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Document and Entity Information Document - USD ($)	12 Months Ended
Document and Entity Information Document - USD ($)	Dec. 31, 2016	Mar. 13, 2017	Jun. 24, 2016
Document and Entity Information [Abstract]
Entity Registrant Name	FORMFACTOR INC.
Entity Central Index Key	0001039399
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding (in shares)		71,652,152
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 456,272,004

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015
Current assets:
Cash and cash equivalents	$ 101,408	$ 146,264
Marketable securities	7,497	41,325
Accounts receivable, net	70,225	36,725
Inventories, net	59,806	27,223
Restricted cash	106	0
Refundable income taxes	1,391	0
Prepaid expenses and other current assets	14,276	6,481
Total current assets	254,709	258,018
Restricted cash	1,082	435
Property, plant and equipment, net	42,663	23,853
Goodwill	188,010	30,731
Intangibles, net	126,608	25,552
Deferred tax assets	3,310	3,281
Other assets	2,600	853
Total assets	618,982	342,723
Current liabilities:
Accounts payable	34,075	18,072
Accrued liabilities	30,184	21,507
Current portion of term loan	12,701	0
Income taxes payable	442	110
Deferred revenue	5,305	3,892
Total current liabilities	82,707	43,581
Long-term income taxes payable	1,315	1,069
Term loan, less current portion	125,475	0
Deferred tax liabilities	3,703	0
Deferred rent and other liabilities	4,726	3,392
Total liabilities	217,926	48,042
Commitments and contingencies (Note 11)
Stockholders' equity:
10,000,000 shares authorized; no shares issued and outstanding at December 31, 2016 and December 26, 2015	0	0
250,000,000 shares authorized; 70,907,847 and 58,088,969 shares issued and outstanding at December 31, 2016 and December 26, 2015, respectively	71	58
Additional paid-in capital	833,341	718,904
Accumulated other comprehensive loss	(3,740)	(2,222)
Accumulated deficit	(428,616)	(422,059)
Total stockholders' equity	401,056	294,681
Total liabilities and stockholders' equity	$ 618,982	$ 342,723

CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - $ / shares	Dec. 31, 2016	Dec. 26, 2015
Statement of Financial Position [Abstract]
Preferred stock par value (in USD per share)	$ 0.001	$ 0.001
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in USD per share)	$ 0.001	$ 0.001
Common stock authorized (in shares)	250,000,000	250,000,000
Common stock issued (in shares)	70,907,847	58,088,969
Common stock outstanding (in shares)	70,907,847	58,088,969

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Income Statement [Abstract]
Revenues	$ 383,881	$ 282,358	$ 268,530
Cost of revenues	281,199	196,620	191,091
Gross profit	102,682	85,738	77,439
Operating expenses:
Research and development	57,453	44,184	42,725
Selling, general and administrative	73,444	45,090	51,385
Restructuring and impairment charges, net	19,692	567	3,887
Total operating expenses	150,589	89,841	97,997
Operating loss	(47,907)	(4,103)	(20,558)
Interest income, net	327	285	302
Other income (expense), net	(2,615)	2,547	161
Loss before income taxes	(50,195)	(1,271)	(20,095)
Provision (benefit) from income taxes	(43,638)	252	(910)
Net loss	$ (6,557)	$ (1,523)	$ (19,185)
Net loss per share:
Basic and diluted (in USD per share)	$ (0.10)	$ (0.03)	$ (0.34)
Weighted-average number of shares used in per share calculations:
Basic and diluted (in shares)	64,941	57,850	55,908

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (6,557)	$ (1,523)	$ (19,185)
Other comprehensive loss, net of tax:
Foreign currency translation adjustments	(2,042)	(397)	(1,502)
Unrealized gains (losses) on available-for-sale marketable securities	29	(64)	(10)
Unrealized gains on derivative instruments	495	0	0
Other comprehensive loss, net of tax	(1,518)	(461)	(1,512)
Comprehensive loss	$ (8,075)	$ (1,984)	$ (20,697)

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balances at Dec. 28, 2013	$ 294,086	$ 55	$ 695,631	$ (249)	$ (401,351)
Balances (in shares) at Dec. 28, 2013		54,649,600
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld	1	$ 1
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld (in shares)		1,282,442
Issuance of common stock under the Employee Stock Purchase Plan	2,812	$ 1	2,811
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		586,386
Stock-based compensation	13,234		13,234
Components of other comprehensive loss:
Change in unrealized gain (loss) on marketable securities, net of tax	(10)			(10)
Foreign currency translation adjustments	(1,502)			(1,502)
Unrealized Gain (loss) on derivative instruments, net of tax	0
Net loss	(19,185)				(19,185)
Balances at Dec. 27, 2014	289,436	$ 57	711,676	(1,761)	(420,536)
Balances (in shares) at Dec. 27, 2014		56,518,428
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash	209		209
Issuance of common stock pursuant to exercise of options for cash (in shares)		24,607
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld	2	$ 2
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld (in shares)		1,993,603
Issuance of common stock under the Employee Stock Purchase Plan	3,206		3,206
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		565,493
Issuance of common stock pursuant to Cascade Microtech acquisition	(8,211)	$ (1)	(8,210)
Purchase and retirement of common stock (in shares)		(1,013,162)
Stock-based compensation	12,023		12,023
Components of other comprehensive loss:
Change in unrealized gain (loss) on marketable securities, net of tax	(64)			(64)
Foreign currency translation adjustments	(397)			(397)
Unrealized Gain (loss) on derivative instruments, net of tax	0
Net loss	(1,523)				(1,523)
Balances at Dec. 26, 2015	$ 294,681	$ 58	718,904	(2,222)	(422,059)
Balances (in shares) at Dec. 26, 2015	58,088,969	58,088,969
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash	$ 2,003		2,003
Issuance of common stock pursuant to exercise of options for cash (in shares)		232,190
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld	2	$ 2
Issuance of common stock pursuant to vesting of restricted stock units, net of stock withheld (in shares)		1,579,218
Issuance of common stock under the Employee Stock Purchase Plan	3,741	$ 1	3,740
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		557,281
Issuance of common stock pursuant to Cascade Microtech acquisition	97,079	$ 10	97,069
Purchase and retirement of common stock (in shares)		10,450,189
Stock-based compensation	11,625		11,625
Components of other comprehensive loss:
Change in unrealized gain (loss) on marketable securities, net of tax	29			29
Foreign currency translation adjustments	(2,042)			(2,042)
Unrealized Gain (loss) on derivative instruments, net of tax	495			495
Net loss	(6,557)				(6,557)
Balances at Dec. 31, 2016	$ 401,056	$ 71	$ 833,341	$ (3,740)	$ (428,616)
Balances (in shares) at Dec. 31, 2016	70,907,847	70,907,847

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Cash flows from operating activities:
Net loss	$ (6,557)	$ (1,523)	$ (19,185)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	46,798	23,771	30,491
(Accretion) amortization of discount on investments	(31)	(10)	208
Stock-based compensation expense	10,722	11,575	13,279
Amortization of debt issuance costs	307	0	0
Deferred income tax (benefit) provision	(45,022)	(14)	230
Provision for doubtful accounts receivable	15	18	1
Provision for excess and obsolete inventories	6,631	6,493	7,127
Acquired inventory step-up amortization	10,022	0	0
(Gain) loss on disposal and write-off of long-lived assets	361	(1,009)	(10)
Impairment of long-lived assets	12,400	8	1,219
Non-cash restructuring	964	500	600
Foreign currency transaction (gains) losses	(77)	(275)	2,489
Gain on derivative instruments	(51)	0	0
Changes in assets and liabilities:
Accounts receivable	(6,847)	8,261	(15,949)
Inventories	(11,733)	(8,167)	(11,975)
Prepaid expenses and other current assets	(3,292)	173	(822)
Refundable income taxes	126	782	0
Other assets	(248)	250	25
Accounts payable	3,433	(2,036)	4,155
Accrued liabilities	786	(333)	7,765
Income taxes payable	(1,127)	19	(1,511)
Deferred rent and other liabilities	126	52	248
Deferred revenues	(283)	(2,413)	(726)
Net cash provided by operating activities	17,423	36,122	17,659
Cash flows from investing activities:
Acquisition of property, plant and equipment	(11,521)	(8,640)	(5,670)
Acquisition of Cascade Microtech, net of cash acquired	(228,031)	0	0
Proceeds from sale of subsidiary	47	53	115
Proceeds from sale of intellectual property and property, plant and equipment	53	1,200	1,114
Purchases of marketable securities	(10,587)	(66,234)	(31,693)
Proceeds from maturities of marketable securities	44,500	74,750	73,473
Change in restricted cash	(779)	0	0
Net cash (used in) provided by investing activities	(206,318)	1,129	37,339
Cash flows from financing activities:
Proceeds from issuances of common stock	5,745	3,418	2,813
Purchase and retirement of common stock	0	(8,210)	0
Proceeds from term loan debt	150,000	0	0
Payments on term loan debt	(10,625)	0	0
Payments of term loan debt issuance costs	(1,506)	0	0
Payments of term loan debt issuance costs	0	0	(271)
Net cash provided by (used in) financing activities	143,614	(4,792)	2,542
Effect of exchange rate changes on cash and cash equivalents	425	(135)	(2,796)
Net increase (decrease) in cash and cash equivalents	(44,856)	32,324	54,744
Cash and cash equivalents, beginning of year	146,264	113,940	59,196
Cash and cash equivalents, end of year	101,408	146,264	113,940
Non-cash investing and financing activities:
Fair value of stock issued in connection with the acquisition of Cascade Microtech	97,080	0	0
Changes in accounts payable and accrued liabilities related to property, plant and equipment purchases	(732)	361	(122)
Supplemental disclosure of cash flow information:
Income and property taxes paid, net	3,667	27	950
Cash paid for interest	$ 2,110	$ 0	$ 0

Formation and Business of the Company	12 Months Ended
Formation and Business of the Company	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Business of the Company	Formation and Business of the Company FormFactor, Inc. ("FormFactor" or the "Company" and also referred to as "we" or "our") was incorporated in Delaware on April 15, 1993 and is headquartered in Livermore, California. We are a leading provider of test and measurement solutions. We provide a broad range of high-performance probe cards, analytical probes, probe stations, thermal sub-systems and reliability test systems to both semiconductor companies and scientific institutions. Our products provide electrical information from a variety of semiconductor and electro-optical devices and integrated circuits (devices) from development to production. Customers use our products and services to lower production costs, improve yields, and enable development of complex next generation devices. We believe our technology leadership enables critical roadmap advances for our customers. On June 24, 2016, we acquired Cascade Microtech Inc. ("Cascade Microtech") which designs, develops, manufactures and markets advanced wafer probing, thermal and reliability solutions for the electrical measurement and testing of high performance semiconductor devices. Design, development and manufacturing operations are located in Beaverton, Oregon, United States and Munich and Thiendorf, Germany, and sales, service and support operations are located in the United States, Germany, Japan, Taiwan, China and Singapore. The acquisition of Cascade Microtech transforms our business into a broader test and measurement market leader with significant scale and increased diversification and demand for the combined company’s products and technologies. Fiscal Year Our fiscal year ends on the last Saturday in December. The fiscal years ended on December 31, 2016, December 26, 2015 and December 27, 2014 consisted of 53 weeks, 52 weeks and 52 weeks, respectively. The first three fiscal quarters in our fiscal year ended December 31, 2016 contained 13 weeks, and the fourth fiscal quarter contained 14 weeks.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

Basis of Consolidation and Foreign Currency Translation

The consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated.

Our consolidated financial statements as of December 31, 2016 included the consolidated balance sheet of Cascade Microtech as of December 31, 2016 whereas our consolidated statements of operations for the fiscal year ended December 31, 2016 included the financial results of Cascade Microtech only for the third and fourth quarters of fiscal 2016. We excluded the financial results of Cascade Microtech for the second quarter of fiscal 2016 as the one-day stub period between the acquisition of Cascade Microtech on June 24, 2016 and the end of our second quarter of fiscal 2016 on June 25, 2016 was immaterial. See Note 4 to the Consolidated Financial Statements - Acquisition, for further details.

The functional currencies of certain of our foreign subsidiaries are the local currencies and, accordingly, all assets and liabilities of these foreign operations are translated to U.S. Dollars at current period-end exchange rates, and revenues and expenses are translated to U.S. Dollars using average exchange rates in effect during the period. The gains and losses from the foreign currency translation of these subsidiaries' financial statements are included as a separate component of stockholders' equity under “Accumulated other comprehensive income (loss).”

Certain other of our foreign subsidiaries use the U.S. Dollar as their functional currency. Accordingly, monetary assets and liabilities in non-functional currencies of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included in the Consolidated Statements of Operations as incurred.

Use of Estimates

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America ("GAAP") requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Estimates may change as new information is obtained. We believe that the estimates, assumptions and judgments involved in revenue recognition, fair value of marketable securities, fair value of derivative financial instruments used to hedge both foreign currency and interest rate exposures, allowance for doubtful accounts, reserves for product warranty, valuation of obsolete and slow moving inventory, assets acquired and liabilities assumed in business combinations, legal contingencies, valuation of goodwill, the assessment of recoverability of long-lived assets, valuation and recognition of stock-based compensation, provision for income taxes and valuation of deferred tax assets have the greatest potential impact on our consolidated financial statements. Actual results could differ from those estimates.

Business Acquisitions

Our consolidated financial statements include the operations of acquired businesses after the completion of their respective acquisitions. We account for acquired businesses using the acquisition method of accounting. The acquisition method of accounting for acquired businesses requires, among other things, that assets acquired and liabilities assumed be recognized at their estimated fair values as of the acquisition date, and that the fair value of acquired intangibles including in-process research and development (IPR&D) be recorded on the balance sheet. Also, transaction costs are expensed as incurred. Any excess of the purchase price over the assigned fair values of the net assets acquired is recorded as goodwill.

Cash and Cash Equivalents and Marketable Securities

Cash and cash equivalents consist of deposits and financial instruments which are readily convertible into cash and have original maturities of 90 days or less at the time of acquisition. Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We generally classify our marketable securities at the date of acquisition as available-for-sale. These securities are reported at fair value with the related unrealized gains and losses included in "Accumulated other comprehensive income (loss)", a component of stockholder's equity, net of tax. Any unrealized losses which are considered to be other-than-temporary impairments are recorded in "Other income (expense), net" in the Consolidated Statements of Operations. Realized gains (losses) on the sale of marketable securities are determined using the specific-identification method and recorded in "Other income (expense), net" in the Consolidated Statements of Operations.

All of our available-for-sale investments are subject to a periodic impairment review. We record a charge to earnings when a decline in fair value is significantly below cost basis and judged to be other-than-temporary, or have other indicators of impairments. If the fair value of an available-for-sale investment is less than its amortized cost basis, an other-than-temporary impairment is triggered in circumstances where (1) we intend to sell the instrument, (2) it is more likely than not that we will be required to sell the instrument before recovery of its amortized cost basis or (3) a credit loss exists where we do not expect to recover the entire amortized cost basis of the instrument. If we intend to sell or it is more likely than not that we will be required to sell the available-for-sale investment before recovery of its amortized cost basis, we recognize an other-than- temporary impairment charge equal to the entire difference between the investment's amortized cost basis and its fair value.

Fair Value of Financial Instruments

We have evaluated the estimated fair value of financial instruments using available market information and valuations as provided by third-party sources. The use of different market assumptions and/or estimation methodologies could have a significant effect on the estimated fair value amounts. The fair value of the Company's cash and cash equivalents, accounts receivable, accounts payable and other current liabilities approximate their carrying amounts due to the relatively short maturity of these items. Estimates of fair value of our marketable securities are based on quoted market prices from active markets or third party, market-based pricing sources which we believe to be reliable. These estimates represent the third parties' good faith opinion as to what a buyer in the marketplace would pay for a security in a current sale.

Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical assets or quoted market prices of similar assets from active markets. The three levels of inputs that may be used to measure fair value are as follows:


•	Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets;


•	Level 2 inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and


•	Level 3 valuations are based on unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances.

Each level of input has different levels of subjectivity and difficulty involved in determining fair value.

Foreign Exchange Management

We transact business in various foreign currencies. We enter into forward foreign exchange contracts in an effort to mitigate the risks associated with currency fluctuations on certain foreign currency balance sheet exposures and certain operational costs denominated in local currency impacting our statement of operations. Gains and losses resulting from the impact of currency exchange rate movements on forward foreign exchange contracts designated to offset certain foreign currency balance sheet exposures and certain operational exposures are recognized as "Other income (expense), net" in the Consolidated Statements of Operations in the period in which the exchange rates change. These gains and losses are intended to partially offset the foreign currency exchange gains and losses on the underlying exposures being hedged. We record the fair value of these contracts as of the end of our reporting period in the Consolidated Balance Sheet. We do not use derivative financial instruments for trading or speculative purposes.

Restricted Cash

As of December 31, 2016 and December 26, 2015, restricted cash included in our Consolidated Balance Sheets were $1.2 million and $0.4 million, respectively. Restricted cash is comprised of security provided to one of our facility landlords in the form of letters of credit and for a foreign subsidiary employee retirement obligations.

Inventories

Inventories are stated at the lower of cost (principally standard cost which approximates actual cost on a first-in, first-out basis) or market value. The provision for potentially excess and obsolete inventory is made based on management's analysis of inventory levels and forecasted future sales. On a quarterly basis, we review inventory quantities on hand and on order under non-cancelable purchase commitments in comparison to our past usage and estimated forecast of product demand for the next six to twelve months to determine what inventory quantities, if any, may not be sellable. Based on this analysis, we write down the affected inventory value for estimated excess and obsolescence charges. Once the value is adjusted, the original cost of our inventory less the related inventory write-down represents the new cost basis of such products. Reversal of these write downs is recognized only when the related inventory has been scrapped or sold. Shipping and handling costs are classified as a component of "Cost of revenues" in the Consolidated Statements of Operations.

We design, manufacture and sell a fully custom product into a market that has been subject to cyclicality and significant demand fluctuations. Our products are complex, custom to a specific chip design and have to be delivered on short lead-times. Probe cards are manufactured in low volumes, but for certain materials, the purchases are often subject to minimum order quantities in excess of the actual underlying probe card demand. It is not uncommon for us to acquire production materials and commence production activities based on estimated production yields and forecasted demand prior to or in excess of actual demand for our probe cards. These factors result in normal recurring inventory valuation adjustments to cost of revenues. Aggregate inventory write downs were $6.6 million, $6.5 million and $7.1 million for fiscal 2016, 2015 and 2014, respectively.

When our products have been delivered, but the revenue associated with that product is deferred because the related revenue recognition criteria have not been met, we may defer the related inventory costs. The deferred inventory costs do not exceed the deferred revenue amounts. The deferred inventory costs are classified as a component of "Prepaid expenses and other current assets" in the Consolidated Balance Sheet.

Property, Plant, and Equipment

Property and equipment is stated at cost less accumulated depreciation and amortization. Depreciation is provided on a straight-line method over the following estimated useful lives of the assets: 1 to 5 years for machinery and equipment, 1 to 5 years for computer equipment and software and 1 to 5 years for furniture and fixtures. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Construction-in-progress assets are not depreciated until the assets are placed in service. Upon sale or retirement of assets, the cost and related accumulated depreciation or amortization, are removed from the balance sheet and the resulting gain or loss is reflected in operations.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of identifiable assets acquired and liabilities assumed. For fiscal 2015, we determined that our reporting unit, for purposes of our goodwill impairment analysis, was comprised of one entity-wide reporting unit associated with the design, development, manufacture, sale and support of precision, high performance advanced semiconductor wafer probe card products and solutions. Upon the acquisition of Cascade Microtech on June 24, 2016, we determined that we now operate in two reportable segments consisting of the Probe Cards Segment and Systems Segment, and three operating segments consisting of FormFactor Probes, Cascade Microtech Probes and Systems. We further determined that for purposes of our goodwill impairment analysis, we now have four reporting units consisting of FormFactor Probes, Cascade Microtech Probes, Systems, and Advanced Temperature Test Systems GmbH ("ATT").

The Company first assesses qualitative factors to determine whether it is necessary to perform a two-step quantitative goodwill impairment test. If an entity determines as a result of the qualitative assessment that it is more likely than not that the fair value of a reporting unit is less than its carrying amount, then the quantitative impairment test is required. Otherwise, no further testing is required.

The performance of the quantitative impairment test involves a two-step process. The first step of the impairment test involves comparing the fair value of the applicable reporting unit with its aggregate carrying value, including goodwill. We generally determine the fair value of our reporting unit using a combination of the income approach (that includes the use of the discounted cash flow method) and the market approach (guideline company approach) valuation methodologies. If the carrying amount of a reporting unit exceeds the fair value of that reporting unit, we perform the second step of the quantitative impairment test to determine the amount of impairment loss. The second step of the goodwill impairment test involves comparing the implied fair value of the affected reporting unit's goodwill with the carrying value of that goodwill.

During the fourth quarter of fiscal 2016, we performed our annual goodwill impairment test by assessing qualitative factors and we concluded that our goodwill was not impaired as of December 31, 2016. Our qualitative review included, among other factors, an assessment of our market capitalization which was significantly higher than our book value. The evaluation of goodwill for impairment requires the exercise of significant judgment. In the event of future changes in business conditions, we will be required to reassess and update our forecasts and estimates used in future impairment analyses. If the results of these analyses are lower than current estimates, a material impairment charge may result at that time. Refer to Note 10 to Notes to Consolidated Financial Statements - Goodwill and Intangible Assets, for further details.

Intangible Assets

Intangible assets consist of acquisition related intangible assets and intellectual property. The intangible assets are being amortized over periods which reflect the pattern in which economic benefits of the assets are expected to be realized, over 1 to 10 years. We perform a review of intangible assets when facts and circumstances indicate that the useful life is shorter than originally estimated or that the carrying amount of assets may not be recoverable. Such facts and circumstances include significant adverse changes in the business climate or legal factors; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the intangible assets; and current expectation that the intangible assets will more likely than not be sold or disposed of before the end of their estimated useful lives. We assess the recoverability of identified intangible assets by comparing the projected undiscounted net cash flows associated with the related asset or group of assets over their remaining lives against their respective carrying amounts. Impairments, if any, are based on the excess of the carrying amount over the fair value of those assets.

Impairment of Long-Lived Assets

We test long-lived assets or asset groups such as property, plant and equipment and intangible assets for recoverability when events or changes in circumstances indicate that their carrying amounts may not be recoverable. Circumstances which could trigger a review include, but are not limited to: significant decreases in the market price of the asset; significant adverse changes in the business climate or legal factors; accumulation of costs significantly in excess of the amount originally expected for the acquisition or construction of the asset; current period cash flow or operating losses combined with a history of losses or a forecast of continuing losses associated with the use of the asset; and current expectation that the asset will more likely than not be sold or disposed of before the end of its estimated useful life.

Recoverability is assessed based on the carrying amounts of the asset or asset group and the sum of the undiscounted cash flows expected to result from the use and the eventual disposal of the asset. An impairment loss is recognized when the carrying amount is not recoverable and exceeds fair value. Refer to Note 7 to Notes to Consolidated Financial Statements - Impairment of Long-lived Assets, for additional information.

Concentration of Credit Risk and Other Risks and Uncertainties

Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash equivalents, marketable securities and trade receivables. Our cash equivalents and marketable securities are held in safekeeping by large, credit worthy financial institutions. We invest our excess cash primarily in U.S. banks, government and agency bonds, money market funds and corporate obligations. We have established guidelines relative to credit ratings, diversification and maturities that seek to maintain safety and liquidity. Deposits in these banks may exceed the amounts of insurance provided on such deposits. To date, we have not experienced any losses on our deposits of cash and cash equivalents. We market and sell our products to a narrow base of customers and generally do not require collateral.

The following customers represented greater than 10% of our revenues in fiscal 2016, fiscal 2015 and fiscal 2014:



	Fiscal 2016		Fiscal 2015		Fiscal 2014
Intel	30.1	%	19.6	%	19.7	%
Samsung	*		14.6		*
SK hynix	*		14.3		16.9
Micron	*		11.7		15.0
Total revenues attributable to customers greater than 10%	30.1	%	60.2	%	51.6	%

* Less than 10% of revenues

At December 31, 2016 and December 26, 2015, one customer accounted for 21% and 29% of gross accounts receivable, respectively. We operate in the competitive semiconductor industry, including the Dynamic Random Access Memory, or DRAM, Flash memory, and Foundry & Logic (previously referred to as System-on-Chip, or SoC) markets, which have been characterized by price erosion, rapid technological change, short product life cycles and heightened foreign and domestic competition. Significant technological changes in the industry could adversely affect our operating results.

We are exposed to non-performance risk by counterparties on our derivative instruments used in hedging activities. We seek to minimize risk by diversifying our hedging program across multiple financial institutions. These counterparties are large international financial institutions, and to date no such counterparty has failed to meet its financial obligations to us.

Certain components for our products that meet our requirements are available only from a limited number of suppliers. The rapid rate of technological change and the necessity of developing and manufacturing products with short life cycles may intensify our reliance on such suppliers. The inability to obtain components as required, or to develop alternative sources, if and as required in the future, could result in delays or reductions in product shipments, which in turn could have a material adverse effect on our business, financial condition, results of operations or cash flows.

Revenue Recognition

We recognize revenue when persuasive evidence of a sales arrangement exists, title and risk of loss has transferred to the customer, the selling price is fixed or determinable and collection of the related receivable is reasonably assured. In instances where final acceptance of the deliverable is specified by the customer, revenue is deferred until all acceptance criteria have been met. Revenues from the licensing of our design and manufacturing technology, which have not been material to date, are recognized over the term of the license agreement or when the significant contractual obligations have been fulfilled.

Our transactions may involve the sale of systems and services under multiple element arrangements. Revenue under multiple element arrangements is allocated based on the fair value of each element. A typical multiple element arrangement may include some or all of the following components: products, accessories, installation services and extended warranty contracts. The total sales price is allocated based on the relative fair value of each component. Historically, most of our products are delivered complete and the impact of the relative fair value by component has not been significant. We record deferred revenue for service contracts, extended warranties and customer deposits. Deferred revenue related to service contracts and extended warranties is recognized over the life of the contract based on the stated contractual price, typically one to two years.

We account for tax assessed by a governmental authority that is directly imposed on a revenue-producing transaction (i.e., sales, use, value added) on a net (excluded from revenue) basis.

Warranty Obligations

We offer warranties on certain products and record a liability for the estimated future costs associated with warranty claims at the time revenue is recognized. The warranty liability is based upon historical experience and our estimate of the level of future costs. While we engage in product quality programs and processes, our warranty obligation is affected by product failure rates, material usage and service delivery costs incurred in correcting a product failure. We continuously monitor product returns for warranty and maintain a reserve for the related expenses based upon our historical experience and any specifically identified field failures. As we sell new products to our customers, we must exercise considerable judgment in estimating the expected failure rates. This estimating process is based on historical experience of similar products, as well as various other assumptions that we believe to be reasonable under the circumstances.

We provide for the estimated cost of product warranties at the time revenue is recognized. Warranty costs are reflected in the Consolidated Statement of Operations as a cost of revenues.

A reconciliation of the changes in our warranty liability is as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Balance at beginning of year	$	1,116		$	1,592
Warranty reserve from acquisition-Cascade Microtech	795			—
Accruals	5,254			2,536
Settlements	(4,193		)	(3,012		)
Balance at end of year	$	2,972		$	1,116

Research and Development

Research and development expenses include expenses related to product development, engineering and material costs. All research and development costs are expensed as incurred.

Allowance for Doubtful Accounts

The majority of our trade receivables are derived from sales to large multinational semiconductor manufacturers throughout the world. In order to monitor potential credit losses, we perform ongoing credit evaluations of our customers' financial condition. An allowance for doubtful accounts is maintained based upon our assessment of the expected collectability of all accounts receivable. The allowance for doubtful accounts is reviewed and assessed for adequacy on a quarterly basis. We take into consideration (1) any circumstances of which we are aware of a customer's inability to meet its financial obligations and (2) our judgments as to prevailing economic conditions in the industry and their impact on our customers. If circumstances change, and the financial condition of our customers is adversely affected and they are unable to meet their financial obligations, we may need to take additional allowances, which would result in an increase in our operating expense.

The allowance for doubtful accounts receivable consisted of the following activity for fiscal years 2016, 2015 and 2014 (in thousands):



	Balance at Beginning of Year		Additions		Reductions			Balance at End of Year
Fiscal year ended December 27, 2014	$	265	$	5	$	(4	)	$	266
Fiscal year ended December 26, 2015	266		20		(2		)	284
Fiscal year ended December 31, 2016	$	284	$	62	$	(48	)	$	298

Restructuring Charges

Restructuring charges are comprised of costs related to employee termination benefits, long-lived assets impaired or abandoned, and contract termination costs. The determination of when we accrue for employee termination benefits depends on whether the termination benefits are provided under a one-time benefit arrangement or under an on-going benefit arrangement. For restructuring charges recorded as an on-going benefit arrangement, a liability for post-employment benefits is recorded when payment is probable, the amount is reasonably estimable, and the obligation relates to rights that have vested or accumulated. For restructuring charges recorded as a one-time benefit arrangement, we recognize a liability for employee termination benefits when a plan of termination, approved by management and establishing the terms of the benefit arrangement, has been communicated to employees. The timing of the recognition of one-time employee termination benefits is dependent upon the period of time the employees are required to render service after communication. If employees are not required to render service in order to receive the termination benefits or if employees will not be retained to render service beyond the minimum legal notification period, a liability for the termination benefits is recognized at the communication date. In instances where employees will be retained to render service beyond the minimum legal notification period, the liability for employee termination benefits is measured initially at the communication date based on the fair value of the liability as of the termination date and is recognized ratably over the future service period. We continually evaluate the adequacy of the remaining liabilities under our restructuring initiatives.

We record charges related to long-lived assets to be abandoned when the assets cease to be used. When we cease using a building or other asset with remaining non-cancelable lease payments continuing beyond our use period, we record a liability for remaining payments under lease arrangements, as well as for contract termination costs, that will continue to be incurred under a contract for its remaining term without economic benefit to us at the cease-use date. Given the significance of, and the timing of the execution of such activities, this process is complex and involves periodic reassessments of estimates made at the time the original decisions were made, including evaluating real estate market conditions for expected vacancy periods and sub-lease rents. Although we believe that these estimates accurately reflect the costs of our restructuring plans, actual results may differ, thereby requiring us to record additional provisions or reverse a portion of such provisions.

The Company recorded restructuring charges of $7.3 million, $0.6 million and $2.7 million for fiscal years 2016, 2015 and 2014, respectively. Refer to Note 6, Restructuring Charges, in Notes to Consolidated Financial Statements for further details.

Income Taxes

We utilize the asset and liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statement and tax basis of assets and liabilities using tax rates expected to be in effect during the years in which the basis differences reverse and for operating losses and tax credit carryforwards. We estimate our provision for income taxes and amounts ultimately payable or recoverable in numerous tax jurisdictions around the world. Estimates involve interpretations of regulations and are inherently complex. Resolution of income tax treatments in individual jurisdictions may not be known for many years after completion of any fiscal year. We are required to evaluate the realizability of our deferred tax assets on an ongoing basis to determine whether there is a need for a valuation allowance with respect to such deferred tax assets. A valuation allowance is recorded when it is more likely than not that some or all of the deferred tax assets will not be realized. Significant management judgment is required in determining any valuation allowance recorded against deferred tax assets. In evaluating the ability to recover deferred tax assets, we consider all available positive and negative evidence giving greater weight to our recent cumulative losses and our ability to carryback losses against prior taxable income and, commensurate with objective verifiability, the forecast of future taxable income including the reversal of temporary differences and the implementation of feasible and prudent tax planning strategies.

We recognize and measure uncertain tax positions taken or expected to be taken in a tax return if it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The tax benefits recognized in the consolidated financial statements from such positions are then measured based on the largest benefit that has a greater than 50 percent likelihood of being realized upon ultimate settlement. We report a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. We adjust these reserves in light of changing facts and circumstances, such as the closing of a tax audit or the refinement of an estimate. To the extent that the final tax outcome of these matters is different than the amounts recorded, such differences will impact the provision for income taxes in the period in which such determination is made. The provision for income taxes includes the impact of reserve provisions and changes to reserves that are considered appropriate, as well as the related net interest. We recognize interest and penalties related to unrecognized tax benefits within the income tax provision. Accrued interest and penalties are included within the related tax liability caption line in the consolidated balance sheet.

We file annual income tax returns in multiple taxing jurisdictions around the world. A number of years may elapse before an uncertain tax position is audited and finally resolved. While it is often difficult to predict the final outcome or the timing of resolution of any particular uncertain tax position, we believe that our reserves for income taxes reflect the most likely outcome. We adjust these reserves, as well as the related interest, in light of changing facts and circumstances. Settlement of any particular position could require the use of cash.

Stock-Based Compensation

We recognize compensation expense for all stock-based awards based on the grant-date estimated fair values, net of an estimated forfeiture rate. The value of the portion of the award that is ultimately expected to vest is recognized as expense ratably over the requisite service periods in our Consolidated Statement of Operations. The fair value of stock options is measured using the Black-Scholes option pricing model while the fair value for restricted stock awards and restricted stock units is measured based on the closing market price of our common stock on the date of grant. The fair value of restricted stock awards based on certain market performance criteria is measured using the Monte Carlo simulation pricing model. Refer to note 12 to Notes to Consolidated Financial Statements - Stockholder's Equity, for further details.

Net Loss Per Share

Basic net loss per share is computed by dividing net loss by the weighted-average number of common shares outstanding for the period. Diluted net loss per share is computed giving effect to all potential dilutive common stock, including stock options, restricted stock units and common stock subject to repurchase. Diluted loss per share was based only on the weighted-average number of shares outstanding during that period as the inclusion of any common stock equivalents would have been anti-dilutive.

A reconciliation of the numerator and denominator used in the calculation of basic and diluted net loss per share is as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Numerator:
Net loss used in computing basic and diluted net loss per share	$	(6,557	)	$	(1,523	)	$	(19,185	)
Denominator:
Weighted-average shares used in computing basic net loss per share	64,941			57,850			55,908
Add potentially dilutive securities	—			—			—
Weighted-average shares used in computing basic and diluted net loss per share	64,941			57,850			55,908

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):



	Fiscal Years Ended
	December 31, 2016	December 26, 2015	December 27, 2014
Options to purchase common stock	2,198	2,320	2,874
Restricted stock units	3,113	2,578	—
Employee stock purchase plan	10	8	28
Total potentially dilutive securities	5,321	4,906	2,902

Accumulated Other Comprehensive Loss

Accumulated other comprehensive loss includes foreign currency translation adjustments, unrealized gains on derivative instruments and unrealized losses on available-for-sale securities, net of tax, the impact of which has been excluded from earnings and reflected as components of stockholders' equity as shown below (in thousands):



	December 31, 2016			December 26, 2015
Unrealized loss on marketable securities, net of tax of $364 in fiscal 2016 and $428 in fiscal 2015, respectively	$	(454	)	$	(483	)
Cumulative translation adjustments	(3,781		)	(1,739		)
Unrealized gains on derivative instruments	495			—
Accumulated other comprehensive loss	$	(3,740	)	$	(2,222	)

Balance Sheet Components

12 Months Ended

Dec. 31, 2016

Balance Sheet Components [Abstract]

Balance Sheet Components

Marketable Securities

Marketable securities at December 31, 2016 consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	7,504	$	—	$	(7	)	$	7,497
	$	7,504	$	—	$	(7	)	$	7,497

Marketable securities at December 26, 2015 consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	18,896	$	1	$	(44	)	$	18,853
Agency securities (Federal)	22,484		—		(12		)	22,472
	$	41,380	$	1	$	(56	)	$	41,325

We classify our marketable securities as available-for-sale. All marketable securities represent the investment of funds available for current operations, notwithstanding their contractual maturities. Such marketable securities are recorded at fair value and unrealized gains and losses are recorded in accumulated other comprehensive income until realized.

We typically invest in highly-rated securities with low probabilities of default. Our investment policy requires investments to be rated single-A or better, limits the types of acceptable investments, concentration as to security holder and duration of the investment. The gross unrealized losses on the Company's investments in fiscal 2016 and 2015, respectively, were caused primarily by changes in interest rates.

Our investment portfolio consists of both corporate and government securities that have a maximum maturity of three years. The longer the duration of these securities, the more susceptible they are to changes in market interest rates and bond yields. As yields increase, those securities with a lower yield-at-cost show a mark-to-market unrealized loss. We anticipate recovering the full cost of the securities either as market conditions improve, or as the securities mature. Accordingly, we believe that the unrealized losses are not other-than-temporary. When evaluating the investments for other-than-temporary impairment, we review factors such as the length of time and extent to which fair value has been below the amortized cost basis, review of current market liquidity, interest rate risk, the financial condition of the issuer, as well as credit rating downgrades. As of December 31, 2016 and December 26, 2015, none of our investments had been in a continuous loss position for 12 months or more.

The contractual maturities of marketable securities as of December 31, 2016 and December 26, 2015 were as follows (in thousands):



	December 31, 2016				December 26, 2015
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	7,504	$	7,497	$	33,882	$	33,871
Due after one year to five years	—		—		7,498		7,454
	$	7,504	$	7,497	$	41,380	$	41,325

Asset Retirement Obligations

We account for the fair value of a liability for an asset retirement obligation to be recognized in the period in which it is incurred if a reasonable estimate of fair value can be made. The fair value of the liability is added to the carrying amount of the associated asset and this additional carrying amount is amortized over the life of the asset. Our asset retirement obligation is associated with our commitment to return property subject to operating leases in the People's Republic of China, Taiwan, South Korea, Singapore and Japan to their original condition upon lease termination. We have estimated that as of December 31, 2016, gross expected future cash flows of $1.1 million would be required to fulfill these obligations.

The carrying amount of a majority of the leasehold improvements resulting from asset retirement obligations were fully amortized in prior years and over the original term of the related leases. Leasehold improvements amortization expense was immaterial for each of fiscal years 2016 and 2015.

The following is a reconciliation of the aggregate asset retirement liability associated with our commitment to return property to its original condition upon lease termination (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Asset retirement obligation beginning balance	$	919	$	903
Initial amount recorded for new asset retirement obligation	34		10
Initial amount recorded for new asset retirement obligation upon acquisition of Cascade Microtech	165		—
Currency translation	11		6
Asset retirement obligation ending balance	$	1,129	$	919

The aggregate asset retirement liability was further classified in the Consolidated Balance Sheets as (in thousands):



Other accrued liabilities, current	$	165	$	212
Deferred rent and other liabilities, non-current	964		707
	$	1,129	$	919

Inventories

Net inventories consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Raw materials	$	27,402	$	12,996
Work-in-progress	20,390		12,492
Finished goods	12,014		1,735
	$	59,806	$	27,223

Property, Plant and Equipment

Property, plant and equipment consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Machinery and equipment	$	169,056		$	150,983
Computer equipment and software	30,640			27,951
Furniture and fixtures	6,060			5,380
Leasehold improvements	72,954			67,121
Sub-total	278,710			251,435
Less: Accumulated depreciation and amortization	(241,943		)	(232,005		)
Net long-lived assets	36,767			19,430
Construction-in-progress	5,896			4,423
Total	$	42,663		$	23,853

In fiscal 2016 and 2015, we ceased use of fully depreciated assets with an acquired cost of $1.7 million and $1.6 million, respectively.

As discussed in Note 7 to the Notes to Consolidated Financial Statements - Impairment of Long-lived Assets, in fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. During the fourth quarter of fiscal 2016 and subsequent to the Cascade Microtech acquisition, we were informed by a customer that they had abandoned their project for which this intangible asset was being developed for, and therefore we fully impaired this intangible asset as it had no alternative future use to us.

In fiscal 2015, long-lived asset impairment charges recorded were insignificant. In fiscal 2014, we recorded impairment charges of $1.0 million for manufacturing assets and software that we no longer utilize.

Depreciation and amortization of property, plant and equipment, excluding the impairments charges discussed above, for the fiscal years 2016, 2015 and 2014 was $11.3 million, $10.6 million and $11.7 million, respectively.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Accrued compensation and benefits	$	16,516	$	12,286
Accrued indirect and other taxes	3,634		2,189
Accrued commissions	792		366
Accrued warranty	2,972		1,116
Deferred rent	160		325
Accrued restructuring	434		2
Other accrued expenses	5,676		5,223
	$	30,184	$	21,507

Acquisition

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

Acquisition

On June 24, 2016, we acquired Cascade Microtech pursuant to the Agreement and Plan of Merger dated as of February 3, 2016 (the “Merger Agreement”) between Cascade Microtech and Cardinal Merger Subsidiary, Inc., an Oregon corporation and our wholly owned subsidiary. Cascade Microtech designs, develops, manufactures and markets advanced wafer probing, thermal and reliability solutions for the electrical measurement and testing of high performance semiconductor devices. Design, development and manufacturing operations are located in Beaverton, Oregon, United States and Munich and Thiendorf, Germany, and sales, service and support operations are located in the United States, Germany, Japan, Taiwan, China and Singapore.

In accordance with the terms of the Merger Agreement, each outstanding share of Cascade Microtech common stock was canceled and converted into the right to receive $16.00 in cash, without interest, and 0.6534 of a share of FormFactor common stock. At the effective time of the merger (the “Effective Time”), each in-the-money Cascade Microtech stock option which was outstanding and vested prior to the Effective Time (or that vested as a result of the consummation of the merger) was canceled and converted into the right to receive an amount in cash equal to the excess, if any, of $21.47 over the applicable per share exercise price of such option. Each out-of-the-money vested option to purchase shares of Cascade Microtech common stock was canceled without any cash payment. Also at the Effective Time, each Cascade Microtech restricted stock unit which was outstanding and vested immediately prior to the Effective Time (or that vested as a result of the consummation of the Merger) was canceled and converted into the right to receive an amount of cash (without interest) equal to $21.47 per share underlying such restricted stock unit.

Additionally, all of the equity awards originally granted by Cascade Microtech which were outstanding and unvested immediately prior to the consummation of the merger (and that did not vest as a result of the consummation of the merger) were assumed by us on substantially the same terms at the Effective Time, except that the number of shares of our common stock that underlie the assumed award and the exercise price of any assumed option were determined pursuant to a formula intended to preserve the intrinsic value of the original award, resulting in the assumption of stock options exercisable for an aggregate of 152,276 shares of our common stock and restricted stock units representing 777,444 shares of our common stock as of the acquisition date. The fair value of the stock options assumed was determined using a Black-Scholes valuation model with market-based assumptions. The fair value of the restricted stock units assumed was $8.92 per unit, based on the FormFactor closing stock price on June 24, 2016. The fair value of unvested equity awards relating to future services, and not yet earned, will be recorded as operating expense over the remaining service periods. Option pricing models require the use of highly subjective market assumptions, including expected stock price volatility, which if changed can materially affect fair value estimates. See Note 12 to the Consolidated Financial Statements - Stockholder’s Equity, for further details.

The acquisition was accounted for using the acquisition method of accounting in accordance with the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") Topic No. 805, Business Combinations, with FormFactor treated as the acquirer. The acquired assets and liabilities of Cascade Microtech were recorded at their respective fair values including an amount for goodwill representing the difference between the acquisition consideration and the fair value of the identifiable net assets. As a result of the acquisition, Cascade Microtech shares ceased to trade on the NASDAQ Global Market effective June 24, 2016.

The total acquisition consideration of $325.1 million, net of cash acquired of $40.7 million was determined based on the terms of the Merger Agreement which consisted of the a) payment of $255.9 million in cash to former shareholders of Cascade Microtech, b) issuance of 10,450,189 shares of FormFactor's common stock to former shareholders of Cascade Microtech which was valued at the closing market price of $8.92 per share on June 24, 2016 and amounted to $93.2 million in the aggregate, c) payment of $12.8 million at the commencement of the third quarter of fiscal 2016, in cash, to Cascade Microtech outstanding and vested equity award holders, and d) $3.9 million attributable to the fair value of the assumed unvested equity awards for services performed by Cascade Microtech employees for the period leading up to the effective date of the acquisition.

During fiscal 2016, we incurred approximately $6.5 million in transaction costs related to the acquisition, which primarily consisted of investment banking, legal, accounting and valuation-related expenses. These expenses were recorded in selling, general and administrative expense in the accompanying Consolidated Statements of Operations.

To finance a portion of the acquisition consideration, we entered into a credit agreement with certain lenders to provide a senior secured term loan facility in an aggregate amount of $150 million. See Note 5 to the to the Notes to Consolidated Financial Statements - Debt, for further details.

The acquisition price was allocated to the tangible and identified intangible assets acquired and liabilities assumed as of the closing date of the acquisition based upon their respective fair values. Asset categories acquired included working capital, long-term assets and liabilities and identifiable intangible assets, including in-process research and development ("IPR&D"). The allocation of the acquisition price has been prepared on a preliminary basis and changes to that allocation may occur as additional information becomes available.

The fair values assigned to assets acquired and liabilities assumed are based on management’s best estimates and assumptions as of the reporting date and are considered preliminary pending finalization of valuation analyses pertaining to intangible assets acquired, liabilities assumed and tax liabilities assumed including calculation of deferred tax assets and liabilities. Changes to amounts recorded as assets or liabilities may result in corresponding adjustments to goodwill, restructuring and impairment charges, recognized deferred tax assets and liabilities including changes to release of valuation allowance during the measurement period (up to one year from the acquisition date). Any such revisions or changes may be material as we finalize the fair values of the tangible and intangible assets acquired and liabilities assumed.

During the year ended December 31, 2016 and subsequent to the acquisition of Cascade Microtech, we made adjustments to certain identifiable intangible assets (order backlog and customer relationships amounting to $(0.1) million) and accrued liabilities (amounting to $0.5 million) resulting in a net increase to goodwill of approximately $0.4 million.

The table below summarizes the assets acquired and liabilities assumed, as of December 31, 2016 (in thousands):



	Amount
Cash and cash equivalents	$	40,681
Accounts receivable	27,112
Inventory	38,315
Prepaid expenses and other current assets	6,249
Property, plant and equipment	19,875
Other long-term assets	818
Deferred revenue	(1,829		)
Accounts payable and accrued liabilities	(23,370		)
Deferred tax liabilities	(48,993		)
Other long-term liabilities	(960		)
Total tangible assets acquired and liabilities assumed	57,898
Intangible assets	149,753
Goodwill	158,141
Total acquisition price	$	365,792

The intangible assets as of the closing date of the acquisition included (in thousands):



	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	91,100	4.7
Customer relationships	23,053		6.8
Order backlog	15,600		0.5
Trade names	7,600		3.5
In-process research and development	12,400
Total intangible assets	$	149,753

Indications of fair value of the intangible assets acquired in connection with the acquisition were determined using either the income, market or replacement cost methodologies. The intangible assets are being amortized over periods which reflect the pattern in which economic benefits of the assets are expected to be realized. Order backlog is expected to be fully amortized by the second quarter of fiscal 2017.

Identifiable intangible assets

Developed technology acquired primarily consists of Cascade Microtech’s existing technologies related to engineering and production probes used in testing wafers, manufacturing wafer testing stations, thermal chuck systems, and reliability test systems. A Multi-Period Excess Earnings (MPEE) Method was used to value the developed technologies. Along with the cash flow forecast associated with each developed technology, other key assumptions in MPEE method are remaining life of technology, technology migration pattern (or technology decay curve), level of R&D required to maintain the technology, discount rate and applicable tax rate. Using this approach, the estimated fair values were calculated using expected future cash flows from specific products discounted to their net present values at an appropriate risk-adjusted rate of return that resulted in a value of $91.1 million and will be amortized over their useful lives.

Customer relationships represent the fair value of future projected revenues that will be derived from the sale of products to existing customers of the acquired company. The fair value of the customer relationships is determined based on the With and Without Method and resulted in a value of $23.1 million which will be amortized over their useful lives. The With and Without Method is appropriate for valuing non-primary customer-related assets for which reasonable estimates can be made for both the time and resources required to recreate those assets, as well as the economic impact over the period of time in which the assets are recreated. The Without scenario incorporates lost revenue and lost profits over the period necessary to retain the asset. Key assumptions in this valuation are attrition rate, time to recreate customer relationships, composition of costs into fixed versus variable costs, tax rates and discount rates.

Trade names and trademarks are considered a type of guarantee of a certain level of quality or performance represented by the brands owned including the Cascade Microtech brand. Trade names and trademarks were valued using the “relief-from-royalty income” approach. This method is based on the assumption that in lieu of ownership, a market participant would be willing to pay a royalty in order to exploit the related benefits of this asset. Key assumptions involved in valuation of trade names include royalty rate, expected utilization of the trade names, tax rates and discount rates. The value of the trade names acquired was determined to be $7.6 million and will be amortized over their useful lives.

IPR&D represents the estimated fair values of incomplete Cascade Microtech research and development projects that had not reached commercialization stage and meet the criteria for recognition as IPR&D as described in the American Institute of Certified Public Accountants IPR&D guide as of the date of the acquisition. In the future, the fair value of each project at the acquisition date will be either amortized or impaired depending on whether the projects are completed or abandoned. The fair value of IPR&D was determined using the MPEE method. For IPR&D, costs to complete the project and expected commercialization timeline are considered as key assumptions. This method reflects the present value of the projected cash flows that are expected to be generated by the IPR&D less charges representing the contribution of other assets to those cash flows. The value of the IPR&D was determined to be $12.4 million and the amortization will commence upon completion of the IPR&D projects. In the fourth quarter of fiscal 2016, we fully impaired this $12.4 million IPR&D intangible asset. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.

Goodwill

The excess of purchase price over the fair value amounts assigned to the assets acquired and liabilities assumed represents the amount of goodwill resulting from the acquisition. We believe the factors that contributed to goodwill include synergies that are specific to our consolidated business such as cost savings and operational efficiencies and the acquisition of a talented workforce that expands our expertise in business development and commercializing semiconductor test products, none of which qualify for recognition as a separate intangible asset. We do not expect any portion of this goodwill to be deductible for tax purposes. The goodwill attributable to the acquisition has been recorded as a non-current asset and is not amortized, but is subject to an annual review for impairment.

The goodwill arising from the acquisition was preliminarily allocated to our reporting units based on the relative fair values of the expected incremental cash flows that the acquisition is expected to provide to each reporting unit within our reportable segments. The allocation of goodwill, which was prepared on a preliminary basis, may be subject to changes as additional information becomes available as the allocation was based on estimates and assumptions made by management at the time of acquisition.

Operating and reporting segments, and reporting units

Upon acquisition of Cascade Microtech, we re-evaluated our operating and reportable segments as well as our reporting units for goodwill impairment consideration in accordance with Financial Accounting Standards Board's Accounting Standards Codification ("ASC") Topics Nos. 280, Segment Reporting and 350, Intangibles-Goodwill and Other. See Note 16 to the Notes to Condensed Consolidated Financial Statements - Operating Segments and Geographic Information, for further details.

Pro forma consolidated results of operations

The following unaudited pro forma results of operations for the year ended December 31, 2016 and December 26, 2015 presents the combined results of operations of FormFactor and Cascade Microtech as if the acquisition had been completed at the beginning of fiscal 2015. The pro forma information includes adjustments to amortization and depreciation for intangible assets and property, plant and equipment, adjustments to stock-based compensation expense, interest expense for the incremental indebtedness incurred, and interest income for the cash paid in connection with the transaction. The pro forma results for the year ended December 26, 2015 include non-recurring adjustments related to deferred tax asset valuation allowance release of $44.0 million which increases pro-forma net income, and acquisition-related transaction costs of $14.4 million and restructuring charges of $7.3 million which decreases pro-forma net income.

The pro forma results also include utilization of the net increase in the cost basis of acquired inventory and acquisition related expenses. The pro forma data are for informational purposes only and are not necessarily indicative of the consolidated results of operations of the combined business had the acquisition actually occurred at the beginning of fiscal year 2015 and 2016 or of the results of future operations of the combined business. Consequently, actual results may differ from the unaudited pro forma information presented below (in thousands, except per share data):



	Twelve Months Ended
	December 31, 2016			December 26, 2015
Revenues	$	455,713		$	426,336
Net loss	(20,641		)	(15,469		)
Net loss per share - basic	$	(0.27	)	$	(0.23	)
Net loss per share - diluted	$	(0.27	)	$	(0.23	)

- Definition

The entire disclosure for a business combination (or series of individually immaterial business combinations) completed during the period, including background, timing, and recognized assets and liabilities. The disclosure may include leverage buyout transactions (as applicable).

+ References

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+ Details

Debt

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Debt

Senior Secured Term Loan Facility

Our debt as of December 31, 2016 consisted of the following (in thousands):



	December 31, 2016
Senior secured term loan	$	139,375
Less debt issuance costs	(1,199		)
Total debt less debt issuance costs	$	138,176

On June 24, 2016, we entered into a Credit Agreement (the “Credit Agreement”) with HSBC Bank USA, National Association ("HSBC"), as administrative agent, co-lead arranger, sole bookrunner and syndication agent, other lenders that may from time-to-time be a party to the Credit Agreement, and certain guarantors. Pursuant to the Credit Agreement, the lenders have provided us with a senior secured term loan facility of $150 million (the “Term Loan”). The proceeds of the Term Loan were used to finance a portion of the purchase price paid in connection with the Cascade Microtech acquisition and to pay related bank fees and expenses.

The Term Loan bears interest at a rate equal to, at our option, (i) the applicable London Interbank Offered Rate ("LIBOR") rate plus 2.00% per annum or (ii) Base Rate (as defined in the Credit Agreement) plus 1.00% per annum. We have initially elected to pay interest at 2.00% over the one-month LIBOR rate. Interest payments are payable in quarterly installments over a five-year period. The Term Loan will amortize in equal quarterly installments, beginning June 30, 2016, in an annual amount equal to 5% for year one, 10% for year two, 20% for year three, 30% for year four and 35% for year five.

On July 25, 2016, we entered into an interest-rate swap agreement with HSBC and other lenders to hedge the interest payments on our Term Loan entered into on June 24, 2016. See Note 8 to Notes to Consolidated Financial Statements - Derivative Financial Instruments, for further details.

The obligations under the Term Loan are and will be fully and unconditionally guaranteed by certain of our existing and subsequently acquired or organized direct and indirect domestic subsidiaries and are secured by a perfected first priority security interest in substantially all of our assets and the assets of those guarantors, subject to certain customary exceptions. See Note 11 to Notes to Consolidated Financial Statements - Commitments and Contingencies, for a schedule of our principal and interest payment commitments under the Term Loan.

The Credit Agreement contains negative covenants customary for financing of this type, including covenants that place limitations on the incurrence of additional indebtedness, the creation of liens, the payment of dividends; dispositions; fundamental changes, including mergers and acquisitions; loans and investments; sale leasebacks; negative pledges; transactions with affiliates; changes in fiscal year; sanctions and anti-bribery laws and regulations, and modifications to charter documents in a manner materially adverse to the Lenders. The Credit Agreement also contains affirmative covenants and representations and warranties customary for financing of this type.

In addition, the Credit Agreement contains financial maintenance covenants requiring, at the end of, and for, each period of four consecutive fiscal quarters, beginning as of June 30, 2016, (a) a ratio of total debt to earnings before interest, taxes, depreciation and amortization ("EBITDA") not in excess of 2.75 to 1.00, stepping down to 2.50 to 1.00 at the end of the fiscal quarter ending June 30, 2017; and (b) a fixed charge coverage ratio of not less than 1.50 to 1.00, stepping down to 1.30 to 1.00 at the end of the fiscal quarter ending June 30, 2018 and to 1.20 to 1.00 at the end of the fiscal quarter ending June 30, 2019. As of December 31, 2016, the Company was in compliance with all of the financial covenants under the senior secured term loan facility.

The Credit Agreement contains customary events of default, including (subject to certain materiality thresholds and grace periods) payment default, failure to comply with covenants, material inaccuracy of representation or warranty, bankruptcy or insolvency proceedings, change of control, certain material Employee Retirement Security Act ("ERISA") events and cross event of default and cross-acceleration in respect of other material debt.

The foregoing description of the Credit Agreement does not purport to be complete and is subject to and qualified in its entirety by reference to the full text of the Credit Agreement, which is filed as Exhibit 10.1 to our Current Report on Form 8-K filed on June 28, 2016.

Restructuring Charges

12 Months Ended

Dec. 31, 2016

Restructuring Charges [Abstract]

Restructuring Charges

Restructuring charges are comprised of costs related to employee termination benefits, cost of long-lived assets abandoned or impaired, as well as contract termination costs. Restructuring charges are included in "Restructuring and impairment charges, net" in the Consolidated Statements of Operations. A summary of the actions we have taken during fiscal 2016, 2015, and 2014, the purpose of which were to improve operating efficiency, streamline and simplify our operations and reduce our operating costs, are discussed below.

2016 Restructuring Activities

During fiscal 2016, we recorded;

• approximately $0.8 million of severance charges and $0.3 million of stock-based compensation expense relating to the modification of certain equity-based awards as a result of the consolidation of our operations;

• approximately $5.4 million of severance charges and $0.7 million of stock-based compensation expense relating to the acceleration of certain equity-based awards of certain executives of Cascade Microtech who were terminated upon our acquisition of Cascade Microtech and in accordance with their contractual change of control agreements; and

• approximately $0.1 million of cease use charges relating to abandoned facilities no longer to be used in our operations.

The cash payments associated with the restructuring activities are expected to be completed by the end of the second quarter of fiscal 2017.

2015 Restructuring Activities

During fiscal 2015, we recorded restructuring charges of approximately $0.6 million which included stock-based compensation expense of approximately $0.5 million relating to the modification of an equity-based award.

2014 Restructuring Activities

On January 27, 2014, we announced a global organizational restructuring and cost reduction plan. As part of the plan, the Company eliminated 52 full-time employees. In addition, we reduced our temporary workforce by 9 positions. We recorded $2.0 million of restructuring charges during the first quarter of fiscal 2014, which was comprised of $1.4 million in severance and related benefits and $0.6 million in impairment charges for certain equipment that would no longer be utilized. During the remainder of fiscal 2014, we further eliminated an additional 5 full-time positions and recorded $0.7 million in severance charges.

The following table summarizes the activities related to the restructuring actions from fiscal 2014 to 2016 (in thousands):



	Employee Severance and Benefits			Property and Equipment Impairment			Contract Termination and Other Costs			Stock-based Compensation			Total
Accrual at December 28, 2013	$	138		$	—		$	—		$	—		$	138
Restructuring charges	2,068			600			—			—			2,668
Asset impairments	—			(600		)	—			—			(600		)
Cash payments	(1,620		)	—			—			—			(1,620		)
Non-cash settlements	(2		)	—			—			—			(2		)
Accrual at December 27, 2014	584			—			—			—			584
Restructuring charges	59			—			500			—			559
Cash payments	(641		)	—			—			—			(641		)
Non-cash settlements	—			—			(500		)	—			(500		)
Accrual at December 26, 2015	2			—			—			—			2
Restructuring charges	6,220			—			104			964			7,288
Cash payments	(5,892		)	—			—			—			(5,892		)
Non-cash settlements	—			—						(964		)	(964		)
Accrual at December 31, 2016	$	330		$	—		$	104		$	—		$	434

Impairment of Long-lived Assets

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment Impairment or Disposal [Abstract]

Impairment of Long-lived Assets

The following table summarizes the components of the impairments that we recorded in fiscal 2016, 2015 and 2014 (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Impairment of long-lived assets:
Assets held for sale	$	—	$	—	$	191
Assets to be disposed of other than by sale	12,400		8		1,028
Total	$	12,400	$	8	$	1,219

Assets held for sale

In fiscal 2016 and 2015, we did not record any impairment charge on assets held for sale and there were no long-lived assets classified as held for sale as of December 31, 2016 and December 26, 2015.

During fiscal 2014, we reclassified $0.6 million of building and $0.5 million of machinery and equipment from "Property, plant and equipment, net" to "Prepaid expenses and other current assets" in our Consolidated Balance Sheet as these assets were identified as held for sale. In the same fiscal year, we recorded a gain of $0.2 million and $52.0 thousand on the sale of the building and machinery and equipment, respectively. In addition, we also recorded a $0.2 million impairment charge related to machinery and equipment which was held for sale. There were no long-lived assets classified as held for sale as of December 27, 2014.

These impairments were included within "Restructuring and Impairment Charges, net" in the Consolidated Statement of Operations for their respective periods.

Assets to be disposed of other than by sale

We test long-lived assets or asset groups for recoverability when events or changes in circumstances indicate that their carrying amounts may not be recoverable. In fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. During the fourth quarter of fiscal 2016 and subsequent to the Cascade Microtech acquisition, we were informed by a customer that they had abandoned their project for which this intangible asset was being developed for, and therefore we fully impaired this intangible asset as it had no alternative future use to us.

All of these charges are included in "Restructuring and Impairment Charges, net" in the Consolidated Statements of Operations for their respective periods.

Refer to Note 10 to the Notes to Consolidated Financial Statements - Goodwill and Intangible Assets for further details relating to our intangible long-lived assets.

Derivative Financial Instruments

12 Months Ended

Dec. 31, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Financial Instruments

Foreign Currency Derivatives

We operate and sell our products in various global markets. As a result, we are exposed to changes in foreign currency exchange rates. We utilize foreign currency forward contracts to hedge against future movements in foreign exchange rates that affect certain existing foreign currency denominated assets and liabilities and forecasted foreign currency revenue and expense transactions. Under this program, our strategy is to have increases or decreases in our foreign currency exposures offset by gains or losses on the foreign currency forward contracts to mitigate the risks and volatility associated with foreign currency transaction gains or losses. We do not use derivative financial instruments for speculative or trading purposes. For accounting purposes, our foreign currency forward contracts are not designated as hedging instruments as defined under ASC 815, Derivatives and Hedging. We record the fair value of these contracts as of the end of our reporting period to our Consolidated Balance Sheets with changes in fair value recorded within "Other income (expense), net" in our Consolidated Statement of Operations for both realized and unrealized gains and losses.

The following table provides information about our foreign currency forward contracts outstanding as of December 31, 2016 (in thousands):



Currency	Contract Position	Contract Amount (Local Currency)		Contract Amount (U.S. Dollars)
Taiwan Dollar	Buy	(42,660	)	$	(1,326	)
Korean Won	Buy	(1,806,386	)	(1,508		)
Euro	Buy	(2,500	)	(2,774		)
Japanese Yen	Sell	1,548,535		13,252
Euro	Sell	2,732		2,876
Euro	Sell	15,877		17,852
Japanese Yen	Sell	136,000		1,288
Total USD notional amount of outstanding foreign exchange contracts				$	29,660

The contracts were entered into during the fourth quarter of fiscal 2016 and will mature during the first quarter of fiscal 2017. Our foreign currency contracts are classified within Level 2 of the fair value hierarchy as they are valued using pricing models that utilize observable market inputs.

The location and amount of gains (losses) related to non-designated derivative instruments that matured in fiscal 2016 and 2015 in the Consolidated Statements of Operations are as follows (in thousands):



		Fiscal Years Ended
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized on Derivatives	December 31, 2016		December 26, 2015
Foreign exchange forward contracts	Other income (expense), net	$	139	$	(310	)

Interest Rate Swaps

Pursuant to our interest rate and risk management strategy, on July 25, 2016, we entered into interest-rate swap agreements with HSBC and other lenders to hedge the interest payments on our Term Loan entered into on June 24, 2016. The Term Loan has a LIBOR based floating interest rate and matures on March 31, 2021. As future levels of LIBOR over the life of the loan are uncertain, we entered into these interest-rate swap agreements to hedge the exposure in interest rate risks associated with movement in LIBOR rates. See Note 5 to Notes to Consolidated Financial Statements - Debt, for further details of the Term Loan.

For accounting purposes, the interest-rate swap contracts qualify for and are designated as cash flow hedges as defined under ASC 815, Derivatives and Hedging. All hedging relationships are formally documented, and the hedges are designed to offset changes to future cash flows on hedged transactions. We recognize derivative instruments from hedging activities as either assets or liabilities on the balance sheet and measure them at fair value on a quarterly basis. We record changes in the effective portion of our cash flow hedges in accumulated other comprehensive income on the Consolidated Balance Sheets, until the forecasted transaction occurs. Amounts expected to be reclassified from other comprehensive income into earnings in the next twelve months were insignificant. We evaluate hedge effectiveness at hedge inception and on an ongoing basis, and record any ineffective portion of the hedge in "Other income (expense), net" in our Consolidated Statement of Operations. We recorded approximately $51 thousand of hedge ineffectiveness for fiscal 2016. The cash flows associated with the interest rate swaps are reported in net cash provided by operating activities on the Consolidated Statements of Cash Flows.

The estimated fair value of the interest rate swaps as of December 31, 2016 was reported as a derivative asset of approximately $0.8 million, recorded within other assets (non-current) on the Company's Consolidated Balance Sheet.

The impact of the cash flow hedges on the consolidated financial statements is depicted below (in thousands):



The Effect of Derivative Instruments on the Statement of Financial Performance
For the Twelve Months Ended
	Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)				Location of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)						Location of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )	Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )

Derivatives in ASC 815 Cash Flow Hedging Relationships

	December 31, 2016		December 26, 2015				December 31, 2016			December 26, 2015				December 31, 2016		December 26, 2015
Interest rate contracts	$	628	$	—	Other income (expense), net		$	(160	)	$	—	Other income (expense), net		$	51	$	—
Total	$	628	$	—			$	(160	)	$	—			$	51	$	—

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

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+ Details

Fair Value

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value

We use fair value measurements to record adjustments to certain financial and non-financial assets and to determine fair value disclosures. The carrying amounts of certain of our financial instruments, including cash and cash equivalents, accounts receivable, accounts payable, accrued compensation and other accrued liabilities, approximate fair value because of their short maturities. Our marketable securities are financial assets recorded at fair value on a recurring basis.

The accounting standards for fair value defines fair value, establishes a framework for measuring fair value and requires disclosures about fair value measurements. Fair value is defined as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities required to be recorded at fair value, we consider the principal or most advantageous market in which we would transact and consider assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions and risk of nonperformance. The accounting standard establishes a fair value hierarchy that requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The standard describes a fair value hierarchy based on three levels of inputs, the first two of which are considered observable and the last unobservable. We apply the following fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows:


•	Level 1—Quoted prices in active markets for identical assets or liabilities;


•	Level 2—Inputs, other than the quoted prices in active markets, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and


•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

We obtain the fair value of our Level 1 investments in certain money market funds, at the expected market price. These investments are expected to maintain a net asset value of $1 per share.

We determine the fair value of our Level 2 financial instruments from several third-party asset managers, custodian banks, and the accounting service providers. Independently, these service providers use professional pricing services to gather pricing data, which may include quoted market prices for identical or comparable instruments or inputs other than quoted prices that are observable either directly or indirectly.

We utilize the market approach to measure the fair value of our fixed income securities. The market approach is a valuation technique that uses prices and other relevant information generated by market transactions involving identical or comparable assets or liabilities. The fair value of our fixed income securities is obtained using readily-available market prices from a variety of industry standard data providers, large financial institutions and other third-party sources for the identical underlying securities.

Our fair value processes include controls that are designed to ensure appropriate fair values are recorded. Such controls include model validation, review of key model inputs, analysis of period-over-period fluctuations and independent recalculation of prices.

Assets Measured at Fair Value on a Recurring Basis

We measure and report certain assets and liabilities at fair value on a recurring basis, including money market funds, U.S. Treasury securities, agency securities and derivatives comprised of foreign currency forward contracts and interest-rate swap contracts (see Note 8 to the Notes to Consolidated Financial Statements - Derivative Financial Instruments, for further details).

Assets measured on a recurring basis as of December 31, 2016 (in thousands):



	Level 1		Level 2		Total
Assets:
Cash equivalents
Money market funds	$	19,350	$	—	$	19,350
Marketable securities
U.S. Treasuries	—		7,497		7,497
Foreign exchange derivative contracts	—		1,137		1,137
Interest rate swap derivative contracts	—		838		838
Total	$	19,350	$	9,472	$	28,822

Assets measured on a recurring basis as of December 26, 2015 (in thousands):



	Level 1		Level 2		Total
Assets:
Cash equivalents
Money market funds	$	82,935	$	—	$	82,935
Marketable securities
U.S. Treasuries	—		18,853		18,853
Agency securities (Federal)	—		22,472		22,472
Total	$	82,935	$	41,325	$	124,260

The Level 1 assets consist of our money market fund deposits. The Level 2 assets consist of our available-for-sale investment portfolio, which are valued utilizing a market approach. Our investments are priced by pricing vendors who provided observable inputs for their pricing without applying significant judgment. Broker pricing is used mainly when a quoted price is not available, the investment is not priced by our pricing vendors or when a broker price is more reflective of fair values in the market in which the investment trades. Our broker-priced investments are labeled as Level 2 investments because fair values of these investments are based on similar assets without applying significant judgments. In addition, all of our investments have a sufficient level of trading volume to demonstrate that the fair values used are appropriate for these investments.

Derivative assets and liabilities include foreign currency forward contracts and interest rate swap contracts. The fair value of foreign currency forward contracts represents the estimated amount required to settle the contracts using current market exchange rates, and is based on the current foreign currency exchange rates and forward points. The fair value of interest rate swaps is estimated based on valuation models that use interest rate yield curves as inputs. The inputs used to estimate the fair value of the Company's derivatives are classified as Level 2.

We did not have any transfers of assets measured at fair value on a recurring basis to or from Level 1 and Level 2 during fiscal 2016 and 2015.

Assets Measured at Fair Value on a Non-recurring Basis

We measure and report goodwill and intangible assets at fair value on a non-recurring basis if we determine these assets to be impaired or in the period when we make a business acquisition. Refer to Note 10 to Notes to Consolidated Financial Statements-Goodwill and Intangible Assets, for further details. The only assets that were measured at fair value on a nonrecurring basis during fiscal 2016 related to the Cascade Acquisition. See Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details. There were no assets measured at fair value on a non-recurring basis during fiscal 2015.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Goodwill and Intangible Assets

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Goodwill recorded from the acquisition of Cascade Microtech on June 24, 2016 was $158.1 million as of December 31, 2016. The Company determined the total consideration paid for its acquisition of Cascade Microtech as well as the fair value of the assets acquired and liabilities assumed as of the acquisition date. The fair values assigned to assets acquired and liabilities assumed are based on management’s best estimates and assumptions as of the reporting date and are considered preliminary pending finalization of valuation analyses pertaining to intangible assets acquired, liabilities assumed and tax liabilities assumed including calculation of deferred tax assets and liabilities. Changes to amounts recorded as assets or liabilities may result in corresponding adjustments to goodwill, recognized deferred tax assets and liabilities including changes to release of valuation allowance during the measurement period (up to one year from the acquisition date). Any such revisions or changes may be material as we finalize the fair values of the tangible and intangible assets acquired and liabilities assumed. See Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details.

Goodwill recorded from the acquisition of MicroProbe Inc. on October 16, 2012 was $30.7 million as of December 31, 2016 and remained unchanged from the amounts recorded as of December 26, 2015.

Upon the acquisition of Cascade Microtech on June 24, 2016 and for purposes of our goodwill impairment analysis, we determined that we now have four reporting units consisting of FormFactor Probes, Cascade Microtech Probes, Systems, and Advanced Temperature Test Systems GmbH ("ATT").

During the fourth quarter of fiscal 2016, we performed our annual goodwill impairment test by assessing qualitative factors and we concluded that our goodwill was not impaired as of December 31, 2016. Our qualitative review included, among other factors, an assessment of our market capitalization which was significantly higher than our book value. Furthermore, the Company has not recorded any historical goodwill impairments as of December 31, 2016. The evaluation of goodwill for impairment requires the exercise of significant judgment. In the event of future changes in business conditions, we will be required to reassess and update our forecasts and estimates used in future impairment analyses. If the results of these analyses are lower than current estimates, a material impairment charge may result at that time.

The changes in intangible assets for fiscal 2016 and the net book value of intangible assets at December 31, 2016 and December 26, 2015 were as follows (in thousands):



	Intangible Assets, Gross Amount								Accumulated Amortization						Intangible Assets, Net					Weight Average Useful Life
Other Intangible Assets (1)	December 26, 2015		Additions/Disposals			December 31, 2016			December 26, 2015		Expense, net		December 31, 2016		December 26, 2015		December 31, 2016			December 31, 2016
Existing developed technologies	$	52,200	$	90,501		$	142,701		$	39,581	$	16,550	$	56,131	$	12,619	$	86,569		4.4
Trade name	4,388		7,533			11,921			1,409		1,580		2,989		2,979		8,932			4.0
Customer relationships	17,000		22,869			39,869			7,046		3,808		10,854		9,954		29,015			5.8
Backlog	—		15,581			15,581			—		13,489		13,489		—		2,092			0.2
Total finite-lived intangible assets	73,588		136,484			210,072			48,036		35,427		83,463		25,552		126,608
IPR&D-addition (2)	—		12,400			12,400			—		—		—		—		12,400
Total intangible assets	73,588		148,884			222,472			48,036		35,427		83,463		25,552		139,008
IPR&D-disposal (2)	—		(12,400		)	(12,400		)	—		—		—		—		(12,400		)
Total intangible assets	$	73,588	$	136,484		$	210,072		$	48,036	$	35,427	$	83,463	$	25,552	$	126,608



(1)	Excludes fully amortized intangible assets.
(2)	In the fourth quarter of fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.

Intangible asset additions during fiscal 2016 related to Cascade Microtech acquisition-see Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details.

We recorded $35.4 million, $13.1 million and $18.8 million, in amortization expense related to our intangible assets in fiscal 2016, 2015, and 2014, respectively. Of the total amortization expense for fiscal 2016, 2015, and 2014, $30.0 million, $10.4 million, and $16.1 million were charged to cost of revenues, respectively, and $5.4 million, $2.7 million and $2.7 million were charged to selling, general and administrative expenses, respectively.

Based on the carrying value of the finite-lived intangible assets recorded as of December 31, 2016, and assuming no subsequent additions to or impairment of the underlying assets, the remaining estimated annual amortization expense is expected to be as follows (in thousands):



Fiscal Year	Amount
2017	$	30,672
2018	28,303
2019	25,639
2020	23,570
2021	12,915
and thereafter	5,509
Total	$	126,608

As of the Effective Date of the acquisition of Cascade Microtech, we began operating under two reportable segments consisting of Probe Cards Segment and Systems Segment. See Note 16 to Notes to Consolidated Financial Statements - Operating Segments and Geographic Information, for further details. The following table summarizes the changes in the carrying amount of goodwill, by reportable segments, for fiscal 2016, applying the segment changes as of June 24, 2016, which was the date when we acquired Cascade Microtech.



	Probe Cards		Systems			Total
	(in thousands)
Goodwill, gross, as of December 27, 2014 and December 26, 2015	$	30,731	$	—		$	30,731
Additions-Cascade Microtech	141,751		16,390			158,141
Foreign currency translation	—		(862		)	(862		)
Balance as of December 31, 2016	$	172,482	$	15,528		$	188,010

Commitments and Contingencies

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Leases

We lease facilities under non-cancellable operating leases with various expiration dates through 2027. The facilities generally require us to pay property taxes, insurance and maintenance costs. Further, several lease agreements contain rent escalation clauses or rent holidays. For purposes of recognizing minimum rental expenses on a straight-line basis over the terms of the leases, we use the date of initial possession to begin amortization. We have the option to extend or renew most of our leases which may increase the future minimum lease commitments.

Rent expense for the fiscal years 2016, 2015, and 2014 was $6.5 million, $4.9 million and $4.8 million, respectively.

Future minimum payments under our non-cancelable operating leases are as follows as of December 31, 2016 (in thousands):



	Operating Leases
Fiscal years:
2017	$	6,279
2018	5,789
2019	4,882
2020	3,581
2021	3,236
Thereafter	15,734
Total	$	39,501

Other Contractual Obligations

The following table sets forth our commitments to settle other contractual obligations in cash as of December 31, 2016 (in thousands):



	Payments Due In Fiscal Years
	2017		2018		2019		2020		2021		Total
	(In thousands)
Purchase obligations	$	33,696	$	4,550	$	515	$	—	$	—	$	38,761
Senior secured term loan facility-principal payments (1)	13,125		26,250		41,250		50,625		8,125		139,375
Senior secured term loan facility-interest payments (2)	2,828		2,400		1,739		821		41		7,829
Total	$	49,649	$	33,200	$	43,504	$	51,446	$	8,166	$	185,965

(1) On June 24, 2016, we entered into a senior secured term loan facility in an aggregate amount of $150 million in order to finance a portion of the Cascade Microtech acquisition consideration. See Note 5 to Notes to Consolidated Financial Statements - Debt, for further details. (2) Represents our minimum interest payment commitments at 2.00% per annum.

Purchase obligations are primarily for purchases of inventory and manufacturing related service contracts. For the purposes of this table, purchase obligations are defined as agreements that are enforceable and legally binding and that specify all significant terms, including: fixed or minimum quantities to be purchased; fixed, minimum or variable price provisions; and the approximate timing of the transaction. The expected timing of payment of the obligations discussed above is estimated based on information available to us as of December 31, 2016. Timing of payments and actual amounts paid may be different depending on the time of receipt of goods or services or changes to agreed-upon amounts for some obligations.

The table above excludes our gross liability for unrecognized tax benefits, which totaled $18.0 million as of December 31, 2016. The timing of any payments which could result from these unrecognized tax benefits will depend upon a number of factors. Accordingly, the timing of payment cannot be estimated and has been excluded from the table above. As of December 31, 2016, the changes to our uncertain tax positions in the next 12 months, that are reasonably possible, are not expected to have a significant impact on our financial position or results of operations.

Environmental Matters

We are subject to U.S. Federal, State, local, and foreign governmental laws and regulations relating to the protection of the environment, including those governing the discharge of pollutants into the air and water, the management and disposal of hazardous substances and wastes, the clean-up of contaminated sites and the maintenance of a safe workplace. We believe that we comply in all material respects with the environmental laws and regulations that apply to us. We did not receive any notices of violations of environmental laws and regulations in fiscal 2016, 2015 or 2014. In the future, we may receive notices of violations of environmental regulations, or otherwise learn of such violations. Environmental contamination or violations may negatively impact our business.

Indemnification Arrangements

We have entered, and may from time to time in the ordinary course of our business enter, into contractual arrangements with third parties that include indemnification obligations. Under these contractual arrangements, we have agreed to defend, indemnify and/or hold the third party harmless from and against certain liabilities. These arrangements include indemnities in favor of customers in the event that our products or services infringe a third party's intellectual property or cause property or other indemnities in favor of our lessors in connection with facility leasehold liabilities that we may cause. In addition, we have entered into indemnification agreements with our directors and certain of our officers, and our bylaws contain indemnification obligations in favor of our directors, officers and agents. These indemnity arrangements may limit the type of the claim, the total amount that we can be required to pay in connection with the indemnification obligation and the time within which an indemnification claim can be made. The duration of the indemnification obligation may vary, and for most arrangements, survives the agreement term and is indefinite. We believe that substantially all of our indemnity arrangements provide either for limitations on the maximum potential future payments we could be obligated to make, or for limitations on the types of claims and damages we could be obligated to indemnify, or both. However, it is not possible to determine or reasonably estimate the maximum potential amount of future payments under these indemnification obligations due to the varying terms of such obligations, a lack of history of prior indemnification claims, the unique facts and circumstances involved in each particular contractual arrangement and in each potential future claim for indemnification, and the contingency of any potential liabilities upon the occurrence of events that are not reasonably determinable. We have not had any material requests for indemnification under these arrangements. We have not recorded any liabilities for these indemnification arrangements on our condensed consolidated balance sheet as of December 31, 2016.

Legal Matters

From time to time, we may be subject to legal proceedings and claims in the ordinary course of business. As of December 31, 2016 and as of the filing of this Annual Report on Form 10-K, we were not involved in any material legal proceedings other than the proceeding summarized below. In the future, we may become a party to additional legal proceedings that may require us to spend significant resources, including proceedings designed to protect our intellectual property rights. Litigation can be expensive and disruptive to normal business operations. Moreover, the results of legal proceedings are difficult to predict, and the costs incurred in litigation can be substantial, regardless of outcome.

On April 8, 2016, an individual plaintiff filed a putative class action lawsuit on behalf of Cascade Microtech’s shareholders against Cascade Microtech, its directors, FormFactor and Cascade Merger Sub, in connection with the acquisition of Cascade Microtech by the Company. The lawsuit, captioned Solak v. Cascade Microtech, Inc., et al., No. 16CV11809, was filed in Multnomah County Circuit Court in the State of Oregon.

The Solak lawsuit alleges that the individual members of Cascade Microtech’s board of directors breached their fiduciary duties owed to Cascade Microtech’s shareholders by approving the proposed merger for inadequate consideration; approving the merger to obtain unique benefits not shared equally with Cascade Microtech’s other shareholders; failing to take steps to maximize the value paid to Cascade Microtech shareholders; failing to take steps to ensure a fair process leading up to the proposed merger; and agreeing to preclusive deal protection devices in the merger agreement. The lawsuit also alleges claims against FormFactor and one of its subsidiaries for aiding and abetting the alleged breaches of fiduciary duties by the individual members of Cascade Microtech’s board of directors.

Under a memorandum of understanding signed by the parties and filed with the court in the Solak case, Cascade Microtech and the Company agreed with the plaintiff’s counsel to supplement the disclosures made in connection with the merger. The supplemental disclosures were made on June 14, 2016. The court in the Solak lawsuit has granted preliminary approval of a stipulated settlement, including an award of the plaintiffs’ attorneys’ fees and expenses. The final resolution of the proceedings under the stipulation of settlement is subject to customary conditions, including final court approval of the class settlement following notice to Cascade Microtech’s former shareholders within the proposed class.

There can be no assurance that the court will approve the final settlement. In such event, the proposed settlement may be terminated.

In August 2013, a former employee filed a class action lawsuit against the Company in the Superior Court of California, alleging violations of California’s wage and hour laws and other claims on behalf of himself and all other similarly situated current and former employees at the Company’s Livermore facilities from August 21, 2009, to the present. On January 4, 2016, the court certified the plaintiff class. The parties have signed a stipulation dated March 3, 2017, regarding the settlement of the class action under which the parties have agreed to settle the lawsuit, subject court approvals and other conditions. The stipulation provides for payment by the Company of $1.5 million in settlement of the lawsuit. As of December 31, 2016, we have accrued in our Consolidated Financial Statements $1.5 million in respect of the potential payment under the stipulation of settlement.

Stockholders' Equity

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Stockholders' Equity

Preferred Stock

We have authorized 10,000,000 shares of undesignated preferred stock, $0.001 par value, none of which is issued and outstanding. Our Board of Directors shall determine the rights, preferences, privileges and restrictions of the preferred stock, including dividends rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of any series.

Common Stock

Each share of common stock has the right to one vote. The holders of common stock are also entitled to receive dividends whenever funds are legally available and when declared by the Board of Directors, subject to the prior rights of holders of all classes of stock outstanding having priority rights as to dividends. No dividends have been declared or paid as of December 31, 2016.

Common Stock Repurchase Program

On April 16, 2015, our Board of Directors authorized a program to repurchase up to $25.0 million of outstanding common stock on the open market and which expired on April 15, 2016. During fiscal 2016, we did not repurchase any shares under this program. During fiscal 2015, we repurchased and retired 1,013,162 shares of common stock for approximately $8.2 million.

In February 2017, our Board of Directors authorized a new program to repurchase up to $25 million of outstanding common stock to offset potential dilution from sales of common stock under our employee stock purchase plan and exercises of stock options. The share repurchase program will expire on February 1, 2020.

Repurchased shares are retired upon the settlement of the related trade transactions. Our policy related to repurchases of our common stock is to charge the excess of cost over par value to additional paid-in capital. All repurchases were made in compliance with Rule 10b-18 under the Securities Exchange Act of 1934, as amended.

Equity Incentive Plan

We currently grant equity-based awards under our Equity Incentive Plan (the "2012 Plan") which was approved by our stockholders at our Annual Meeting of Stockholders on April 18, 2012. On May 1, 2015, at our Annual Meeting of Stockholders, our stockholders further approved the amended and restated 2012 Plan which increased the maximum number of shares of common stock authorized for issuance by an additional 4.5 million shares and prohibited the cashing out of stock appreciation rights.

Restricted stock and restricted stock units granted under the 2012 Plan will generally vest over three years in annual tranches though we also have granted and will continue to grant such awards over a shorter vest term for employee retention purposes. Additionally, restricted shares reduce the shares available for issuance at 1.70 shares for every one share issued.

The 2012 Plan also provides for the grant of incentive stock options, nonqualified stock options and stock appreciation rights. The incentive stock options may be granted to our employees and the nonqualified stock options, and all awards other than incentive stock options, may be granted to employees, directors and consultants. The exercise price of incentive stock options must be at least equal to the fair market value of common stock on the date of grant. All options granted under the 2012 Plan will generally vest over four years and have a term of seven years, unless otherwise determined by the Compensation Committee of the Board of Directors. Stock appreciation rights granted under the 2012 Plan will generally vest over four years in annual tranches. We have not granted any incentive stock options or stock appreciation rights during fiscal 2016 and 2015.

At December 31, 2016, there were 3.5 million shares available for grant under the 2012 Plan.

Stock Options

On June 24, 2016, pursuant to the Agreement and Plan of Merger with Cascade Microtech, we granted 152,276 stock options with a total grant date fair value of approximately $0.8 million, of which approximately $0.3 million was attributable to the fair value of the assumed unvested options for services performed by Cascade Microtech employees for the period leading up to the effective date of the acquisition and which was included as part of the purchase price consideration. See Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details.

Stock option activity is set forth below:



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 26, 2015	2,320,195		$	9.40
Options granted	152,276		4.42
Options exercised	(232,190	)	8.63
Options canceled	(42,250	)	9.87
Outstanding at December 31, 2016	2,198,031		$	9.13	2.02	$	4,825,647
Vested and expected to vest at December 31, 2016	2,171,229		$	9.14	1.97	$	4,735,512
Exercisable at December 31, 2016	1,767,871		$	9.48	1.14	$	3,305,020

On February 9, 2015, we granted 450,000 non-qualified stock options to our Chief Executive Officer with a grant-date fair value of approximately $1.7 million which will be recognized as stock compensation expense ratably over the service period. The following weighted average assumptions were used in the estimated grant-date fair value calculations using the Black-Scholes option pricing model:



Stock Options:
Dividend yield	—	%
Expected volatility	47.5	%
Risk-free interest rate	1.6	%
Expected term (in years)	5.5

Restricted Stock Units

Restricted stock units are converted into shares of our common stock upon vesting on a one-for-one basis. The vesting of restricted stock units is subject to the employee's continuing service to us. Restricted stock unit (RSU) activity is set forth below:



	Number of Shares		Weighted Average Grant Date Fair Value
Restricted stock units at December 28, 2013	2,929,639		$	5.88
Granted	1,900,000		6.52
Vested	(1,282,442	)	6.30
Canceled	(297,151	)	6.17
Restricted stock units at December 27, 2014	3,250,046		6.07
Granted	1,540,250		8.64
Vested	(1,993,603	)	6.00
Canceled	(218,555	)	6.36
Restricted stock units at December 26, 2015	2,578,138		7.63
Granted	2,296,210		8.20
Vested	(1,579,218	)	6.60
Canceled	(182,509	)	6.44
Restricted stock units at December 31, 2016	3,112,621		$	8.65

On June 24, 2016, pursuant to the Agreement and Plan of Merger with Cascade Microtech, we granted 777,444 RSUs with a total grant date fair value of approximately $6.9 million, of which approximately $3.6 million was attributable to the fair value of the assumed unvested RSUs for services performed by Cascade Microtech employees for the period leading up to the effective date of the acquisition and which was included as part of the purchase price consideration. See Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details.

On August 19, 2016, we issued 155,000 RSUs to six senior executives which will vest based on certain market performance criteria. The performance criteria are based on a metric called our Total Shareholder Return (TSR) for the period from April 1, 2016 to March 31, 2019 relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies), as of April 1, 2016. The total stock-based compensation cost of approximately $1.7 million will be recognized ratably over the requisite service period.

On May 2, 2016, we issued 40,000 RSUs to a senior executive which will vest based on certain market performance criteria. The performance criteria are based on a metric called our TSR for the period from April 1, 2016 to March 31, 2019 relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies), as of April 1, 2016. The total stock-based compensation cost of approximately $0.3 million will be recognized ratably over the requisite service period.

On May 28, 2015, we issued 195,000 RSUs to seven senior executives of our company that will vest based on certain market performance criteria. The performance criteria are based on our TSR for the period from April 1, 2015 to March 31, 2017 relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies), as of April 1, 2015. The total stock-based compensation cost of approximately $1.5 million will be recognized ratably over the requisite service period.

On May 5, 2014, we issued 350,000 RSUs to seven senior executives of our company that will vest based on certain market performance criteria. The performance criteria are based on our TSR for the period from April 1, 2014 to March 31, 2016 relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies), as of April 1, 2014. Upon the review of the market performance criteria on April 4, 2016, our Compensation Committee certified a total earn out of 328,600 RSUs which immediately vested as of that date.

The total fair value of restricted stock units vested during fiscal 2016, 2015 and 2014 was $12.0 million, $18.1 million and $8.2 million, respectively.

Employee Stock Purchase Plan

Under the 2012 Employee Stock Purchase Plan ("ESPP"), the offering periods are 12 months commencing on February 1 of each calendar year and ending on January 31 of the subsequent calendar year, and a six-month fixed offering period commencing on August 1 of each calendar year and ending on January 31 of the subsequent calendar year. The 12-month offering period consists of two six-month purchase periods and the six-month offering period consists of one six-month purchase period. The price of the common stock purchased is 85% of the lesser of the fair market value of the common stock on the first day of the applicable offering period or the last day of each purchase period.

During fiscal 2016, 2015, and 2014, employees purchased 557,281 shares, 565,493 shares and 586,386 shares under this program at a weighted average exercise price of $6.71, $5.67 and $4.80, respectively.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.E)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21484-112644

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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+ Details

Stock-Based Compensation

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation

We account for all stock-based compensation to employees and directors, including grants of RSUs and stock options, as stock-based compensation costs based on the fair value measured as of the date of grant. These costs are recognized as an expense in the Consolidated Statements of Operations over the requisite service period.

The table below shows the stock-based compensation expense included in the Consolidated Statement of Operations (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Stock-based compensation expense included in:
Cost of revenues	$	2,518	$	2,651	$	2,433
Research and development	3,329		3,490		3,529
Selling, general and administrative	4,875		5,434		7,317
Total stock-based compensation	10,722		11,575		13,279
Tax effect on stock-based compensation	—		—		—
Total stock-based compensation, net of tax	$	10,722	$	11,575	$	13,279

During fiscal 2016, we recorded approximately $0.3 million of stock-based compensation expense relating to the modification of certain equity-based awards as a result of the consolidation of our operations. In addition, we also recorded approximately $0.7 million of stock-based compensation expense relating to the acceleration of certain equity-based awards of an executive of Cascade Microtech who was terminated upon our acquisition of Cascade Microtech and in accordance with his contractual change of control agreement with Cascade Microtech.

During fiscal 2015, we recorded stock-based compensation expense of approximately $0.5 million relating to the modification of an equity-based award.

We classified these stock-based compensation expenses as restructuring-related expenses. Refer to Note 6 to Notes to Consolidated Financial Statements - Restructuring Charges for further details.

Restricted Stock Units

The fair value of restricted stock units is determined using the market closing price of our common stock on the grant date and compensation cost is recognized over the vesting period on a straight-line basis. The restricted stock units generally vest over three years though we also have granted and will continue to grant such awards over a shorter vest term for employee retention purposes.

During fiscal 2016, 2015 and 2014, we granted 2,296,210 shares, 1,540,250 shares and 1,900,000 shares of restricted stock units with the weighted average grant-date fair values of $8.20, $8.64 and $6.52 per share, respectively. As of December 31, 2016, the unamortized stock-based compensation balance related to restricted stock units was $19.1 million after estimated forfeitures, which will be recognized over an estimated period of 2.20 years based on the weighted average days to vest.

Stock Options

The exercise price of each stock option equals the market price of our stock on the date of grant. Most options are scheduled to vest over three to four years and expire five to ten years from the grant date. The fair value of each option grant is estimated on the date of grant using the Black-Scholes option pricing model. In addition, we estimate forfeitures when recognizing compensation expense, and adjust our estimates of forfeitures over the requisite service period based on the extent to which actual forfeitures differ, or are expected to differ, from such estimates. Changes in estimated forfeitures are recognized as a change in estimate in the period of change and will also impact the amount of compensation expense to be recognized in future periods.

During fiscal 2016, we granted 152,276 stock options pursuant to the Agreement and Plan of Merger with Cascade Microtech acquired on June 24, 2016 with a weighted average grant-date fair value of $4.42 per share. Our computation of expected volatility was based on a combination of historical and market-based implied volatility from traded options on our common stock. We believe that including market-based implied volatility in the calculation of expected volatility results in a more accurate measure of the volatility expected in future periods. Risk-free interest rates are yields for zero-coupon U.S. Treasury notes maturing approximately at the end of the expected option life. We determine the expected term by considering several factors, including historical option exercise behavior, post vesting turnover rates, contractual terms and vesting periods of the options granted.

As of December 31, 2016, the unamortized stock-based compensation balance related to stock options was $1.1 million after estimated forfeitures, which will be recognized over an estimated period of 2.0 years based on the weighted average days to vest.

Employee Stock Purchase Plan

During fiscal 2016, we issued 557,281 shares under our approved employee stock purchase plans. As of December 31, 2016, we had $0.2 million of total unrecognized stock-based compensation expense, which will be recognized over the weighted average period of approximately one month. Compensation expense is calculated using the fair value of the employees' purchase rights under the Black-Scholes model.

The following assumptions were used in estimating the fair value of employees' purchase rights under the approved employee stock purchase plans:



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	45.43	%	51.78	%	41.71	%
Risk-free interest rate	0.43	%	0.12	%	0.09	%
Expected life (in years)	0.8		0.7		0.7

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

Income Taxes

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Income Taxes

The components of loss before income taxes were as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
United States	$	(50,947	)	$	(3,069	)	$	(23,230	)
Foreign	752			1,798			3,135
	$	(50,195	)	$	(1,271	)	$	(20,095	)

The components of the provision for income taxes are as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Current provision (benefit):
Federal	$	—		$	(3	)	$	(983	)
State	120			72			(386		)
Foreign	1,804			198			234
	1,924			267			(1,135		)
Deferred provision (benefit):
Federal	(42,150		)	—			—
State	(2,165		)	—			—
Foreign	(1,247		)	(15		)	225
	(45,562		)	(15		)	225
Total provision (benefit) from income taxes	$	(43,638	)	$	252		$	(910	)

The following is a reconciliation of the difference between income taxes computed by applying the federal statutory rate of 35% and the provision (benefit) from income taxes for fiscal 2016, 2015 and 2014 (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
U.S. statutory federal tax rate	$	(17,568	)	$	(445	)	$	(7,033	)
State taxes and credits, net of Federal benefit	(975		)	17			(186		)
Amortization of stock-based compensation	1,256			907			686
Research and development credits	(1,654		)	(1,872		)	(1,183		)
Foreign taxes at rates different than the U.S.	504			(66		)	(84		)
Other permanent differences	2,048			238			(972		)
Change in valuation allowance	(27,120		)	1,457			7,886
Other	(129		)	16			(24		)
Total	$	(43,638	)	$	252		$	(910	)

Deferred tax assets and liabilities are recognized for the future tax consequences of differences between the carrying amounts of assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to be reversed. Significant deferred tax assets and liabilities consist of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Tax credits	$	33,486		$	30,968
Inventory reserve	13,863			14,010
Unrealized investment gains	—			20
Other reserves and accruals	10,593			5,953
Non-statutory stock options	6,206			4,936
Depreciation and amortization	7,719			13,440
Net operating loss carryforwards	118,482			119,327
Gross deferred tax assets	190,349			188,654
Valuation allowance	(150,581		)	(176,196		)
Total deferred tax assets	39,768			12,458
Acquired intangibles & fixed assets	(39,801		)	(9,177		)
Unrealized investment gains	(289		)	—
Tax on undistributed earnings	(71		)	—
Total deferred tax liabilities	(40,161		)	(9,177		)
Net deferred tax assets (liabilities)	$	(393	)	$	3,281

We are required to evaluate the realizability of our deferred tax assets in both our U.S. and non-U.S. jurisdictions on an ongoing basis to determine whether there is a need for a valuation allowance with respect to such deferred tax assets. During fiscal 2016 and 2015, we maintained a valuation allowance against our U.S. deferred tax assets. We intend to maintain a valuation allowance until sufficient positive evidence exists to support the realization of such deferred tax assets.

The valuation allowance against deferred tax assets consisted of the following activity for the fiscal years 2016, 2015 and 2014 (in thousands):



Description	Balance at Beginning of Year		Additions		Reduction			Balance at End of Year
Allowance against deferred tax assets
Year ended December 31, 2016	$	176,196	$	—	$	(25,615	)	$	150,581
Year ended December 31, 2015	187,759		—		(11,563		)	176,196
Year ended December 31, 2014	$	180,913	$	6,846	$	—		$	187,759

At December 31, 2016, we had Federal research and development tax credit, Federal net operating loss, and foreign tax credit carryforwards of $22.5 million, $298.7 million and $2.2 million, respectively, which will expire at various dates from 2017 through 2036. We had alternative minimum tax credits of $2.4 million which do not expire. We had California and Oregon research credits of $29.9 million and $0.6 million, respectively. The California research credit can be carried forward indefinitely while Oregon research credits expire at various dates from 2017 through 2022. We had state net operating loss carryforwards of approximately $271.7 million, which will expire at various dates from 2017 through 2036. We had Singapore net operating loss carryforwards of approximately $9.7 million, which can be carried forward indefinitely.

We have not provided U.S. Federal and State income taxes, nor foreign withholding taxes, on approximately $20.2 million of undistributed earnings for certain non-US subsidiaries, because such earnings are intended to be indefinitely reinvested. If these earnings were distributed to the U.S. in the form of dividends or otherwise, or if the shares of the relevant foreign subsidiaries were sold or otherwise transferred, we would be subject to additional U.S. income taxes (subject to an adjustment for foreign tax credits) and foreign withholding taxes, of approximately $0.4 million. Determination of the amount of unrecognized deferred tax liability for temporary differences related to investment in these non-U.S. subsidiaries that are essentially permanent in duration is not practicable.

During fiscal 2016 and 2015, there were $1.8 million and $6.3 million, respectively, of unrecognized tax benefit associated with the exercise of employee stock options and other employee stock programs. During fiscal 2014, there were no tax benefits associated with the exercise of employee stock options and other employee stock programs.

The following table reflects changes in the unrecognized tax benefits (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Unrecognized tax benefit beginning balance	$	17,033		$	16,333		$	16,972
Additions based on tax positions related to the current year	614			667			498
Additions based on tax position from prior year	450			163			324
Reductions for tax positions of prior years	—			(18		)	(1,109		)
Reductions to unrecognized tax benefits due to lapse of the applicable statute of limitations	(119		)	(112		)	(352		)
Unrecognized tax benefit ending balance	$	17,978		$	17,033		$	16,333

At December 31, 2016, we had total tax-effected unrecognized tax benefits of $18.0 million of which $1.3 million, if recognized, would impact the effective tax rate.

We recognize interest (benefit) charges and penalties related to uncertain tax positions as part of the income tax provision. We recognized interest (benefit) charges and penalties of $22 thousand, $50 thousand and $(0.1) million in fiscal 2016, 2015, and 2014, respectively. As of December 31, 2016 and December 26, 2015, we have accrued total interest charges and penalties of $0.2 million and $0.2 million, respectively, related to uncertain tax positions.

The amount of income taxes we pay is subject to ongoing audits by Federal, State and foreign tax authorities which might result in proposed assessments. Our estimate for the potential outcome for any uncertain tax issue is judgmental in nature. However, we believe we have adequately provided for any reasonably foreseeable outcome related to those matters. Our future results may include favorable or unfavorable adjustments to our estimated tax liabilities in the period the assessments are made or resolved or when statutes of limitation on potential assessments expire. As of December 31, 2016, changes to our uncertain tax positions in the next 12 months that are reasonably possible are not expected to have a significant impact on our financial position or results of operations.

We and our subsidiaries file income tax returns in the U.S. Federal jurisdiction, various states and non U.S. jurisdictions. The material income tax jurisdictions are the United States (Federal), California, Germany, Singapore, China and Japan. The audit of income tax returns for Federal and California for the tax years 2010 to 2012 stub period and 2010 to 2011, respectively, have been settled. However, as a result of net operating loss carryforwards, we are subject to audit for tax years 2007 and forward for Federal purposes and 2008 and forward for California purposes. For Germany, Singapore, China and Japan purposes, we are subject to audit for tax years after 2012.

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans We have an employee savings plan that qualifies as a deferred salary arrangement under Section 401(k) of the Internal Revenue Code. The plan is designed to provide employees with an accumulation of funds for retirement on a tax-deferred basis and provide for annual discretionary employer contributions. The total charge to operations under the 401(k) plan for fiscal 2016, 2015 and 2014 aggregated $0.5 million, $1.1 million and $1.0 million, respectively.

Operating Segment and Geographic Information

12 Months Ended

Dec. 31, 2016

Segment Reporting [Abstract]

Operating Segment and Geographic Information

Operating Segments and Geographic Information

Until the acquisition of Cascade Microtech, we operated in one reportable segment consisting of one operating segment relating to the design, development, manufacture and sale of high performance advanced probe cards. Our chief operating decision maker ("CODM") is our Chief Executive Officer, who reviews operating results to make decisions about allocating resources and assessing performance for the entire company.

Upon the acquisition of Cascade Microtech (See Note 4 to Notes to Consolidated Financial Statements - Acquisition, for further details), we re-evaluated our CODM's decision process for allocating resources and assessing performance for the company and determined that we now operate in two reportable segments consisting of the Probe Cards Segment and Systems Segment.

The following table summarizes the operating results by reportable segments for fiscal 2016 and 2015 (in thousands, except percentages):



	Fiscal 2016
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	337,970		$	45,911		$	—		$	383,881
Gross profit	$	121,407		$	23,925		$	(42,650	)	$	102,682
Gross margin	35.9		%	52.1		%	—		%	26.7		%
Operating income (loss)	$	49,382		$	8,968		$	(106,257	)	$	(47,907	)



	Fiscal 2015
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	282,358		$	—		$	—		$	282,358
Gross profit	$	99,199		$	—		$	(13,461	)	$	85,738
Gross margin	35.1		%	—		%	—		%	30.4		%
Operating income (loss)	$	39,964		$	—		$	(44,067	)	$	(4,103	)

Operating results provide useful information to our management for assessment of our performance and results of operations. Certain components of our operating results are utilized to determine executive compensation along with other measures.

Corporate and other includes unallocated expenses relating to amortization of intangible assets, share-based compensation expense, acquisition-related costs, including charges related to inventory stepped up to fair value, and other costs, which are not used in evaluating the results of, or in allocating resources to, our reportable segments. Acquisition-related costs include transaction costs and any costs directly related to the acquisition and integration of acquired businesses.

The following table summarizes revenue, by geographic region, as a percentage of total revenues based upon ship-to location:



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
United States	33.3	%	23.4	%	28.1	%
South Korea	17.1		25.2		19.6
Taiwan	14.9		21.9		18.4
Europe	12.9		9.0		11.4
Asia-Pacific (1)	11.4		11.1		12.9
Japan	10.0		9.4		9.6
Rest of the world	0.4		—		—
Total Revenues	100.0	%	100.0	%	100.0	%

(1) Asia-Pacific includes all countries in the region except Taiwan, Japan and South Korea, which are disclosed separately.

The following table summarizes revenue by product group (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Foundry & Logic	$	237,591	$	145,839	$	142,360
DRAM	86,910		125,512		110,800
Flash	13,469		11,007		15,370
Systems	45,911		—		—
Total revenues	$	383,881	$	282,358	$	268,530

The following customers represented greater than 10% of our revenues in fiscal 2016, fiscal 2015 and fiscal 2014:



	Fiscal 2016		Fiscal 2015		Fiscal 2014
Intel	30.1	%	19.6	%	19.7	%
Samsung	*		14.6		*
SK hynix	*		14.3		16.9
Micron	*		11.7		15.0
Total revenues attributable to customers greater than 10%	30.1	%	60.2	%	51.6	%

* Less than 10% of revenues

Long-lived assets, comprising of net property, plant and equipment, goodwill and net intangibles assets are reported

based on the location of the asset. Long-lived assets by geographic location are as follows (in thousands):



	December 31, 2016		December 26, 2015
United States	$	323,369	$	77,257
Europe	30,903		655
Asia-Pacific (1)	1,709		689
South Korea	733		1,128
Japan	510		295
Singapore	57		112
Total	$	357,281	$	80,136

(1) Asia-Pacific includes all countries in the region except Taiwan, Japan and South Korea, which are disclosed separately.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
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-Section 50
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+ Details

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data (Unaudited)

The following selected quarterly financial data should be read in conjunction with our consolidated financial statements and the related notes and "Item 7: Management's Discussion and Analysis of Financial Condition and Results of Operations." This information has been derived from our unaudited consolidated financial statements that, in our opinion, reflect all recurring adjustments necessary to fairly present this information when read in conjunction with our consolidated financial statements and the related notes appearing in the section entitled "Consolidated Financial Statements." The results of operations for any quarter are not necessarily indicative of the results to be expected for any future period.



	Fiscal Quarters Ended
	Dec. 31, 2016 (3)			Sep. 24, 2016			June. 25, 2016 (1) (2)			March 26, 2016			Dec. 26, 2015			Sep. 26, 2015 (5)			June. 27, 2015		March 28, 2015 (4)
	(in thousands, except per share data)
Revenues	$	123,888		$	123,299		$	83,083		$	53,611		$	71,782		$	65,862		$	73,885	$	70,829
Cost of revenues	83,613			96,111			57,656			43,819			50,591			47,407			50,582		48,040
Gross profit	40,275			27,188			25,427			9,792			21,191			18,455			23,303		22,789
Operating Expenses:
Research and development	18,218			17,253			11,133			10,849			11,236			10,645			11,217		11,086
Selling, general and administrative	23,890			23,008			14,030			12,516			10,719			11,108			11,381		11,882
Restructuring and impairment charges, net	12,697			85			6,910			—			(3		)	59			8		503
Total operating expenses	54,805			40,346			32,073			23,365			21,952			21,812			22,606		23,471
Operating income (loss)	(14,530		)	(13,158		)	(6,646		)	(13,573		)	(761		)	(3,357		)	697		(682		)
Interest income, net	59			52			88			117			70			65			65		85
Other income (expense), net	(946		)	(1,042		)	(302		)	(314		)	(36		)	982			100		1,501
Income (loss) before income taxes	(15,417		)	(14,148		)	(6,860		)	(13,770		)	(727		)	(2,310		)	862		904
Provision (benefit) for income taxes	26			50			(43,744		)	30			(108		)	215			24		121
Net income (loss)	$	(15,443	)	$	(14,198	)	$	36,884		$	(13,800	)	$	(619	)	$	(2,525	)	$	838	$	783
Net income (loss) per share:
Basic	$	(0.22	)	$	(0.20	)	$	0.62		$	(0.24	)	$	(0.01	)	$	(0.04	)	$	0.01	$	0.01
Diluted	$	(0.22	)	$	(0.20	)	$	0.61		$	(0.24	)	$	(0.01	)	$	(0.04	)	$	0.01	$	0.01
Weighted average number of shares used in per share calculations:
Basic	70,807			70,502			59,572			58,431			58,128			58,209			58,109		56,594
Diluted	70,807			70,502			59,988			58,431			58,128			58,209			59,094		58,838

(1)

In the second quarter of fiscal 2016, we recorded $5.4 million of severance charges and $0.7 million of stock-based compensation expense relating to the acceleration of certain equity-based awards of certain executives of Cascade Microtech who were terminated upon our acquisition of Cascade Microtech and in accordance with their contractual change of control agreements. See Note 6, Restructuring Charges, to the Notes to Consolidated Financial Statements for further details.


(2)	In the second quarter of fiscal 2016, we recorded an income tax benefit of $43.7 million primarily due to the release of valuation allowance of our deferred tax assets in connection with our acquisition of Cascade Microtech. See Note 14, Income Taxes, to the Notes to Consolidated Financial Statements for further details.


(3)	In the fourth quarter of fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.


(4)	In the first quarter of fiscal 2015, we recorded a $1.5 million gain from a business interruption insurance claim relating to a factory fire at a customer. See Note 18, Business Interruption Insurance Claim Recovery, to the Notes to Consolidated Financial Statements for further details.


(5)	In the third quarter of fiscal 2015, we recorded a $1.0 million net gain from the sale of intellectual property.

Business Interruption Insurance Claim Recovery	12 Months Ended
Business Interruption Insurance Claim Recovery	Dec. 31, 2016
Unusual or Infrequent Items, or Both [Abstract]
Business Interruption Insurance Claim Recovery	Business Interruption Insurance Claim Recovery During fiscal 2015, we received approximately $1.5 million as a result of a payment from our insurer arising from a business interruption insurance claim related to a factory fire at a customer during the second half of fiscal 2013. We recorded this cash receipt within “Other income (expense), net” in our Consolidated Statements of Operations.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Fiscal Year

Our fiscal year ends on the last Saturday in December.

Basis of Consolidation

Basis of Consolidation and Foreign Currency Translation

The consolidated financial statements include our accounts and those of our wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated.

Foreign Currency Translation

Use of Estimates

Business Aquisitions

Business Acquisitions

Cash and Cash Equivalents

Cash and Cash Equivalents and Marketable Securities

Cash and cash equivalents consist of deposits and financial instruments which are readily convertible into cash and have original maturities of 90 days or less at the time of acquisition.

Marketable Securities

Marketable securities consist primarily of highly liquid investments with maturities of greater than 90 days when purchased. We generally classify our marketable securities at the date of acquisition as available-for-sale. These securities are reported at fair value with the related unrealized gains and losses included in "Accumulated other comprehensive income (loss)", a component of stockholder's equity, net of tax. Any unrealized losses which are considered to be other-than-temporary impairments are recorded in "Other income (expense), net" in the Consolidated Statements of Operations. Realized gains (losses) on the sale of marketable securities are determined using the specific-identification method and recorded in "Other income (expense), net" in the Consolidated Statements of Operations.

Fair Value of Financial Instruments


•	Level 1 valuations are obtained from real-time quotes for transactions in active exchange markets involving identical assets;


•	Level 2 inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and


•	Level 3 valuations are based on unobservable inputs to the valuation methodology and include our own data about assumptions market participants would use in pricing the asset or liability based on the best information available under the circumstances.

Each level of input has different levels of subjectivity and difficulty involved in determining fair value.

Foreign Exchange Management

Restricted Cash

Inventories

Property, Plant, and Equipment

Goodwill

Intangible Assets

Impairment of Long-Lived Assets

Concentration of Credit Risk and Other Risk and Uncertainties

Concentration of Credit Risk and Other Risks and Uncertainties

Revenue Recognition

We account for tax assessed by a governmental authority that is directly imposed on a revenue-producing transaction (i.e., sales, use, value added) on a net (excluded from revenue) basis.

Warranty Obligations

We provide for the estimated cost of product warranties at the time revenue is recognized. Warranty costs are reflected in the Consolidated Statement of Operations as a cost of revenues.

Research and Development

Research and development expenses include expenses related to product development, engineering and material costs. All research and development costs are expensed as incurred.

Allowance for Doubtful Accounts

Restructuring Charges

Income Taxes

Stock-based Compensation

Stock-Based Compensation

Net Loss Per Share

Accumulated Other Comprehensive Loss

Derivative Financial Instruments

We do not use derivative financial instruments for speculative or trading purposes. For accounting purposes, our foreign currency forward contracts are not designated as hedging instruments as defined under ASC 815, Derivatives and Hedging. We record the fair value of these contracts as of the end of our reporting period to our Consolidated Balance Sheets with changes in fair value recorded within "Other income (expense), net" in our Consolidated Statement of Operations for both realized and unrealized gains and losses.

Fair Value Measurement


•	Level 1—Quoted prices in active markets for identical assets or liabilities;


•	Level 2—Inputs, other than the quoted prices in active markets, such as quoted prices for similar assets or liabilities, quoted prices near the reporting date in markets that are less active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and


•	Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedules of Concentration of Risk, by Customer

The following customers represented greater than 10% of our revenues in fiscal 2016, fiscal 2015 and fiscal 2014:



	Fiscal 2016		Fiscal 2015		Fiscal 2014
Intel	30.1	%	19.6	%	19.7	%
Samsung	*		14.6		*
SK hynix	*		14.3		16.9
Micron	*		11.7		15.0
Total revenues attributable to customers greater than 10%	30.1	%	60.2	%	51.6	%

* Less than 10% of revenues

Schedule of Product Warranty Liability Reconciliation

A reconciliation of the changes in our warranty liability is as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Balance at beginning of year	$	1,116		$	1,592
Warranty reserve from acquisition-Cascade Microtech	795			—
Accruals	5,254			2,536
Settlements	(4,193		)	(3,012		)
Balance at end of year	$	2,972		$	1,116

Schedule of Allowance for Doubtful Accounts

The allowance for doubtful accounts receivable consisted of the following activity for fiscal years 2016, 2015 and 2014 (in thousands):



	Balance at Beginning of Year		Additions		Reductions			Balance at End of Year
Fiscal year ended December 27, 2014	$	265	$	5	$	(4	)	$	266
Fiscal year ended December 26, 2015	266		20		(2		)	284
Fiscal year ended December 31, 2016	$	284	$	62	$	(48	)	$	298

Schedule of Calculation of Numerator and Denominator in Earnings Per Share

A reconciliation of the numerator and denominator used in the calculation of basic and diluted net loss per share is as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Numerator:
Net loss used in computing basic and diluted net loss per share	$	(6,557	)	$	(1,523	)	$	(19,185	)
Denominator:
Weighted-average shares used in computing basic net loss per share	64,941			57,850			55,908
Add potentially dilutive securities	—			—			—
Weighted-average shares used in computing basic and diluted net loss per share	64,941			57,850			55,908

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the periods presented (in thousands):



	Fiscal Years Ended
	December 31, 2016	December 26, 2015	December 27, 2014
Options to purchase common stock	2,198	2,320	2,874
Restricted stock units	3,113	2,578	—
Employee stock purchase plan	10	8	28
Total potentially dilutive securities	5,321	4,906	2,902

Schedule of Accumulated Other Comprehensive Loss



	December 31, 2016			December 26, 2015
Unrealized loss on marketable securities, net of tax of $364 in fiscal 2016 and $428 in fiscal 2015, respectively	$	(454	)	$	(483	)
Cumulative translation adjustments	(3,781		)	(1,739		)
Unrealized gains on derivative instruments	495			—
Accumulated other comprehensive loss	$	(3,740	)	$	(2,222	)

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2016

Balance Sheet Components [Abstract]

Schedule of Marketable Securities

Marketable securities at December 31, 2016 consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	7,504	$	—	$	(7	)	$	7,497
	$	7,504	$	—	$	(7	)	$	7,497

Marketable securities at December 26, 2015 consisted of the following (in thousands):



	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	18,896	$	1	$	(44	)	$	18,853
Agency securities (Federal)	22,484		—		(12		)	22,472
	$	41,380	$	1	$	(56	)	$	41,325

Contractual Maturity of Marketable Securities

The contractual maturities of marketable securities as of December 31, 2016 and December 26, 2015 were as follows (in thousands):



	December 31, 2016				December 26, 2015
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	7,504	$	7,497	$	33,882	$	33,871
Due after one year to five years	—		—		7,498		7,454
	$	7,504	$	7,497	$	41,380	$	41,325

Schedule of Asset Retirement Liability

The following is a reconciliation of the aggregate asset retirement liability associated with our commitment to return property to its original condition upon lease termination (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Asset retirement obligation beginning balance	$	919	$	903
Initial amount recorded for new asset retirement obligation	34		10
Initial amount recorded for new asset retirement obligation upon acquisition of Cascade Microtech	165		—
Currency translation	11		6
Asset retirement obligation ending balance	$	1,129	$	919

The aggregate asset retirement liability was further classified in the Consolidated Balance Sheets as (in thousands):



Other accrued liabilities, current	$	165	$	212
Deferred rent and other liabilities, non-current	964		707
	$	1,129	$	919

Schedule of Net Inventory

Net inventories consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Raw materials	$	27,402	$	12,996
Work-in-progress	20,390		12,492
Finished goods	12,014		1,735
	$	59,806	$	27,223

Schedule of Property, Plant and Equipment

Property, plant and equipment consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Machinery and equipment	$	169,056		$	150,983
Computer equipment and software	30,640			27,951
Furniture and fixtures	6,060			5,380
Leasehold improvements	72,954			67,121
Sub-total	278,710			251,435
Less: Accumulated depreciation and amortization	(241,943		)	(232,005		)
Net long-lived assets	36,767			19,430
Construction-in-progress	5,896			4,423
Total	$	42,663		$	23,853

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015
Accrued compensation and benefits	$	16,516	$	12,286
Accrued indirect and other taxes	3,634		2,189
Accrued commissions	792		366
Accrued warranty	2,972		1,116
Deferred rent	160		325
Accrued restructuring	434		2
Other accrued expenses	5,676		5,223
	$	30,184	$	21,507

Acquisition (Tables)

12 Months Ended

Dec. 31, 2016

Business Combinations [Abstract]

Schedule of Assets Acquired and Liabilities Assumed

The table below summarizes the assets acquired and liabilities assumed, as of December 31, 2016 (in thousands):



	Amount
Cash and cash equivalents	$	40,681
Accounts receivable	27,112
Inventory	38,315
Prepaid expenses and other current assets	6,249
Property, plant and equipment	19,875
Other long-term assets	818
Deferred revenue	(1,829		)
Accounts payable and accrued liabilities	(23,370		)
Deferred tax liabilities	(48,993		)
Other long-term liabilities	(960		)
Total tangible assets acquired and liabilities assumed	57,898
Intangible assets	149,753
Goodwill	158,141
Total acquisition price	$	365,792

Summary of Finite-Lived Intangible Assets Acquired

The intangible assets as of the closing date of the acquisition included (in thousands):



	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	91,100	4.7
Customer relationships	23,053		6.8
Order backlog	15,600		0.5
Trade names	7,600		3.5
In-process research and development	12,400
Total intangible assets	$	149,753

Summary of Indefinite-Lived Intangible Assets Acquired

The intangible assets as of the closing date of the acquisition included (in thousands):



	Amount		Weighted Average Useful Life (in years)
Developed technologies	$	91,100	4.7
Customer relationships	23,053		6.8
Order backlog	15,600		0.5
Trade names	7,600		3.5
In-process research and development	12,400
Total intangible assets	$	149,753

Schedule of Pro Forma Information

The pro forma data are for informational purposes only and are not necessarily indicative of the consolidated results of operations of the combined business had the acquisition actually occurred at the beginning of fiscal year 2015 and 2016 or of the results of future operations of the combined business. Consequently, actual results may differ from the unaudited pro forma information presented below (in thousands, except per share data):



	Twelve Months Ended
	December 31, 2016			December 26, 2015
Revenues	$	455,713		$	426,336
Net loss	(20,641		)	(15,469		)
Net loss per share - basic	$	(0.27	)	$	(0.23	)
Net loss per share - diluted	$	(0.27	)	$	(0.23	)

Debt (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of Debt

Our debt as of December 31, 2016 consisted of the following (in thousands):



	December 31, 2016
Senior secured term loan	$	139,375
Less debt issuance costs	(1,199		)
Total debt less debt issuance costs	$	138,176

Restructuring Charges (Tables)

12 Months Ended

Dec. 31, 2016

Restructuring Charges [Abstract]

Summary of Restructuring Activities

The following table summarizes the activities related to the restructuring actions from fiscal 2014 to 2016 (in thousands):



	Employee Severance and Benefits			Property and Equipment Impairment			Contract Termination and Other Costs			Stock-based Compensation			Total
Accrual at December 28, 2013	$	138		$	—		$	—		$	—		$	138
Restructuring charges	2,068			600			—			—			2,668
Asset impairments	—			(600		)	—			—			(600		)
Cash payments	(1,620		)	—			—			—			(1,620		)
Non-cash settlements	(2		)	—			—			—			(2		)
Accrual at December 27, 2014	584			—			—			—			584
Restructuring charges	59			—			500			—			559
Cash payments	(641		)	—			—			—			(641		)
Non-cash settlements	—			—			(500		)	—			(500		)
Accrual at December 26, 2015	2			—			—			—			2
Restructuring charges	6,220			—			104			964			7,288
Cash payments	(5,892		)	—			—			—			(5,892		)
Non-cash settlements	—			—						(964		)	(964		)
Accrual at December 31, 2016	$	330		$	—		$	104		$	—		$	434

Impairment of Long-lived Assets (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment Impairment or Disposal [Abstract]

Summary of Impairments of Long-lived Assets

The following table summarizes the components of the impairments that we recorded in fiscal 2016, 2015 and 2014 (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Impairment of long-lived assets:
Assets held for sale	$	—	$	—	$	191
Assets to be disposed of other than by sale	12,400		8		1,028
Total	$	12,400	$	8	$	1,219

Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Foreign Currency Forward Contracts Outstanding

The following table provides information about our foreign currency forward contracts outstanding as of December 31, 2016 (in thousands):



Currency	Contract Position	Contract Amount (Local Currency)		Contract Amount (U.S. Dollars)
Taiwan Dollar	Buy	(42,660	)	$	(1,326	)
Korean Won	Buy	(1,806,386	)	(1,508		)
Euro	Buy	(2,500	)	(2,774		)
Japanese Yen	Sell	1,548,535		13,252
Euro	Sell	2,732		2,876
Euro	Sell	15,877		17,852
Japanese Yen	Sell	136,000		1,288
Total USD notional amount of outstanding foreign exchange contracts				$	29,660

Schedule of Non-designated Derivative Gains (Losses)



		Fiscal Years Ended
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized on Derivatives	December 31, 2016		December 26, 2015
Foreign exchange forward contracts	Other income (expense), net	$	139	$	(310	)

Schedule of the Impact of Cash Flow Hedges on Consolidated Financial Statements

The impact of the cash flow hedges on the consolidated financial statements is depicted below (in thousands):



The Effect of Derivative Instruments on the Statement of Financial Performance
For the Twelve Months Ended
	Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)				Location of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)						Location of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )	Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )

Derivatives in ASC 815 Cash Flow Hedging Relationships

	December 31, 2016		December 26, 2015				December 31, 2016			December 26, 2015				December 31, 2016		December 26, 2015
Interest rate contracts	$	628	$	—	Other income (expense), net		$	(160	)	$	—	Other income (expense), net		$	51	$	—
Total	$	628	$	—			$	(160	)	$	—			$	51	$	—

Fair Value (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Schedule of Fair Values Measured on Recurring Basis

Assets measured on a recurring basis as of December 31, 2016 (in thousands):



	Level 1		Level 2		Total
Assets:
Cash equivalents
Money market funds	$	19,350	$	—	$	19,350
Marketable securities
U.S. Treasuries	—		7,497		7,497
Foreign exchange derivative contracts	—		1,137		1,137
Interest rate swap derivative contracts	—		838		838
Total	$	19,350	$	9,472	$	28,822

Assets measured on a recurring basis as of December 26, 2015 (in thousands):



	Level 1		Level 2		Total
Assets:
Cash equivalents
Money market funds	$	82,935	$	—	$	82,935
Marketable securities
U.S. Treasuries	—		18,853		18,853
Agency securities (Federal)	—		22,472		22,472
Total	$	82,935	$	41,325	$	124,260

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2016

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Finite-lived Intangible Assets

The changes in intangible assets for fiscal 2016 and the net book value of intangible assets at December 31, 2016 and December 26, 2015 were as follows (in thousands):



	Intangible Assets, Gross Amount								Accumulated Amortization						Intangible Assets, Net					Weight Average Useful Life
Other Intangible Assets (1)	December 26, 2015		Additions/Disposals			December 31, 2016			December 26, 2015		Expense, net		December 31, 2016		December 26, 2015		December 31, 2016			December 31, 2016
Existing developed technologies	$	52,200	$	90,501		$	142,701		$	39,581	$	16,550	$	56,131	$	12,619	$	86,569		4.4
Trade name	4,388		7,533			11,921			1,409		1,580		2,989		2,979		8,932			4.0
Customer relationships	17,000		22,869			39,869			7,046		3,808		10,854		9,954		29,015			5.8
Backlog	—		15,581			15,581			—		13,489		13,489		—		2,092			0.2
Total finite-lived intangible assets	73,588		136,484			210,072			48,036		35,427		83,463		25,552		126,608
IPR&D-addition (2)	—		12,400			12,400			—		—		—		—		12,400
Total intangible assets	73,588		148,884			222,472			48,036		35,427		83,463		25,552		139,008
IPR&D-disposal (2)	—		(12,400		)	(12,400		)	—		—		—		—		(12,400		)
Total intangible assets	$	73,588	$	136,484		$	210,072		$	48,036	$	35,427	$	83,463	$	25,552	$	126,608



(1)	Excludes fully amortized intangible assets.
(2)	In the fourth quarter of fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.

Schedule of Indefinite-lived Intangible Assets

The changes in intangible assets for fiscal 2016 and the net book value of intangible assets at December 31, 2016 and December 26, 2015 were as follows (in thousands):



	Intangible Assets, Gross Amount								Accumulated Amortization						Intangible Assets, Net					Weight Average Useful Life
Other Intangible Assets (1)	December 26, 2015		Additions/Disposals			December 31, 2016			December 26, 2015		Expense, net		December 31, 2016		December 26, 2015		December 31, 2016			December 31, 2016
Existing developed technologies	$	52,200	$	90,501		$	142,701		$	39,581	$	16,550	$	56,131	$	12,619	$	86,569		4.4
Trade name	4,388		7,533			11,921			1,409		1,580		2,989		2,979		8,932			4.0
Customer relationships	17,000		22,869			39,869			7,046		3,808		10,854		9,954		29,015			5.8
Backlog	—		15,581			15,581			—		13,489		13,489		—		2,092			0.2
Total finite-lived intangible assets	73,588		136,484			210,072			48,036		35,427		83,463		25,552		126,608
IPR&D-addition (2)	—		12,400			12,400			—		—		—		—		12,400
Total intangible assets	73,588		148,884			222,472			48,036		35,427		83,463		25,552		139,008
IPR&D-disposal (2)	—		(12,400		)	(12,400		)	—		—		—		—		(12,400		)
Total intangible assets	$	73,588	$	136,484		$	210,072		$	48,036	$	35,427	$	83,463	$	25,552	$	126,608



(1)	Excludes fully amortized intangible assets.
(2)	In the fourth quarter of fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.

Schedule of Remaining Estimated Amortization Expense



Fiscal Year	Amount
2017	$	30,672
2018	28,303
2019	25,639
2020	23,570
2021	12,915
and thereafter	5,509
Total	$	126,608

Schedule of Goodwill [Table Text Block]

The following table summarizes the changes in the carrying amount of goodwill, by reportable segments, for fiscal 2016, applying the segment changes as of June 24, 2016, which was the date when we acquired Cascade Microtech.



	Probe Cards		Systems			Total
	(in thousands)
Goodwill, gross, as of December 27, 2014 and December 26, 2015	$	30,731	$	—		$	30,731
Additions-Cascade Microtech	141,751		16,390			158,141
Foreign currency translation	—		(862		)	(862		)
Balance as of December 31, 2016	$	172,482	$	15,528		$	188,010

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Operating Lease Payments

Future minimum payments under our non-cancelable operating leases are as follows as of December 31, 2016 (in thousands):



	Operating Leases
Fiscal years:
2017	$	6,279
2018	5,789
2019	4,882
2020	3,581
2021	3,236
Thereafter	15,734
Total	$	39,501

Schedule of Commitments to Settle Other Obligations

The following table sets forth our commitments to settle other contractual obligations in cash as of December 31, 2016 (in thousands):



	Payments Due In Fiscal Years
	2017		2018		2019		2020		2021		Total
	(In thousands)
Purchase obligations	$	33,696	$	4,550	$	515	$	—	$	—	$	38,761
Senior secured term loan facility-principal payments (1)	13,125		26,250		41,250		50,625		8,125		139,375
Senior secured term loan facility-interest payments (2)	2,828		2,400		1,739		821		41		7,829
Total	$	49,649	$	33,200	$	43,504	$	51,446	$	8,166	$	185,965

Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Equity [Abstract]

Schedule of Stock Option Activity

Stock option activity is set forth below:



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 26, 2015	2,320,195		$	9.40
Options granted	152,276		4.42
Options exercised	(232,190	)	8.63
Options canceled	(42,250	)	9.87
Outstanding at December 31, 2016	2,198,031		$	9.13	2.02	$	4,825,647
Vested and expected to vest at December 31, 2016	2,171,229		$	9.14	1.97	$	4,735,512
Exercisable at December 31, 2016	1,767,871		$	9.48	1.14	$	3,305,020

Schedule of Weighted Average Assumptions

The following weighted average assumptions were used in the estimated grant-date fair value calculations using the Black-Scholes option pricing model:



Stock Options:
Dividend yield	—	%
Expected volatility	47.5	%
Risk-free interest rate	1.6	%
Expected term (in years)	5.5

Schedule of Restricted Stock Unit Activity

Restricted stock unit (RSU) activity is set forth below:



	Number of Shares		Weighted Average Grant Date Fair Value
Restricted stock units at December 28, 2013	2,929,639		$	5.88
Granted	1,900,000		6.52
Vested	(1,282,442	)	6.30
Canceled	(297,151	)	6.17
Restricted stock units at December 27, 2014	3,250,046		6.07
Granted	1,540,250		8.64
Vested	(1,993,603	)	6.00
Canceled	(218,555	)	6.36
Restricted stock units at December 26, 2015	2,578,138		7.63
Granted	2,296,210		8.20
Vested	(1,579,218	)	6.60
Canceled	(182,509	)	6.44
Restricted stock units at December 31, 2016	3,112,621		$	8.65

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock-based Compensation Expense

The table below shows the stock-based compensation expense included in the Consolidated Statement of Operations (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Stock-based compensation expense included in:
Cost of revenues	$	2,518	$	2,651	$	2,433
Research and development	3,329		3,490		3,529
Selling, general and administrative	4,875		5,434		7,317
Total stock-based compensation	10,722		11,575		13,279
Tax effect on stock-based compensation	—		—		—
Total stock-based compensation, net of tax	$	10,722	$	11,575	$	13,279

Schedule of Assumptions, Fair Value of Employee Purchase Rights

The following assumptions were used in estimating the fair value of employees' purchase rights under the approved employee stock purchase plans:



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	45.43	%	51.78	%	41.71	%
Risk-free interest rate	0.43	%	0.12	%	0.09	%
Expected life (in years)	0.8		0.7		0.7

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of Components of Loss Before Income Taxes

The components of loss before income taxes were as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
United States	$	(50,947	)	$	(3,069	)	$	(23,230	)
Foreign	752			1,798			3,135
	$	(50,195	)	$	(1,271	)	$	(20,095	)

Schedule of Components of Provision for Income Taxes

The components of the provision for income taxes are as follows (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Current provision (benefit):
Federal	$	—		$	(3	)	$	(983	)
State	120			72			(386		)
Foreign	1,804			198			234
	1,924			267			(1,135		)
Deferred provision (benefit):
Federal	(42,150		)	—			—
State	(2,165		)	—			—
Foreign	(1,247		)	(15		)	225
	(45,562		)	(15		)	225
Total provision (benefit) from income taxes	$	(43,638	)	$	252		$	(910	)

Schedule of Effective Income Tax Rate Reconciliation



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
U.S. statutory federal tax rate	$	(17,568	)	$	(445	)	$	(7,033	)
State taxes and credits, net of Federal benefit	(975		)	17			(186		)
Amortization of stock-based compensation	1,256			907			686
Research and development credits	(1,654		)	(1,872		)	(1,183		)
Foreign taxes at rates different than the U.S.	504			(66		)	(84		)
Other permanent differences	2,048			238			(972		)
Change in valuation allowance	(27,120		)	1,457			7,886
Other	(129		)	16			(24		)
Total	$	(43,638	)	$	252		$	(910	)

Schedule of Deferred Tax Assets and Liabilities

Significant deferred tax assets and liabilities consist of the following (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015
Tax credits	$	33,486		$	30,968
Inventory reserve	13,863			14,010
Unrealized investment gains	—			20
Other reserves and accruals	10,593			5,953
Non-statutory stock options	6,206			4,936
Depreciation and amortization	7,719			13,440
Net operating loss carryforwards	118,482			119,327
Gross deferred tax assets	190,349			188,654
Valuation allowance	(150,581		)	(176,196		)
Total deferred tax assets	39,768			12,458
Acquired intangibles & fixed assets	(39,801		)	(9,177		)
Unrealized investment gains	(289		)	—
Tax on undistributed earnings	(71		)	—
Total deferred tax liabilities	(40,161		)	(9,177		)
Net deferred tax assets (liabilities)	$	(393	)	$	3,281

Summary of Valuation Allowance Against Deferred Tax Assets

The valuation allowance against deferred tax assets consisted of the following activity for the fiscal years 2016, 2015 and 2014 (in thousands):



Description	Balance at Beginning of Year		Additions		Reduction			Balance at End of Year
Allowance against deferred tax assets
Year ended December 31, 2016	$	176,196	$	—	$	(25,615	)	$	150,581
Year ended December 31, 2015	187,759		—		(11,563		)	176,196
Year ended December 31, 2014	$	180,913	$	6,846	$	—		$	187,759

Schedule of Unrecognized Tax Benefits

The following table reflects changes in the unrecognized tax benefits (in thousands):



	Fiscal Years Ended
	December 31, 2016			December 26, 2015			December 27, 2014
Unrecognized tax benefit beginning balance	$	17,033		$	16,333		$	16,972
Additions based on tax positions related to the current year	614			667			498
Additions based on tax position from prior year	450			163			324
Reductions for tax positions of prior years	—			(18		)	(1,109		)
Reductions to unrecognized tax benefits due to lapse of the applicable statute of limitations	(119		)	(112		)	(352		)
Unrecognized tax benefit ending balance	$	17,978		$	17,033		$	16,333

Operating Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2016

Segment Reporting [Abstract]

Operating Results by Reportable Segments

The following table summarizes the operating results by reportable segments for fiscal 2016 and 2015 (in thousands, except percentages):



	Fiscal 2016
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	337,970		$	45,911		$	—		$	383,881
Gross profit	$	121,407		$	23,925		$	(42,650	)	$	102,682
Gross margin	35.9		%	52.1		%	—		%	26.7		%
Operating income (loss)	$	49,382		$	8,968		$	(106,257	)	$	(47,907	)



	Fiscal 2015
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	282,358		$	—		$	—		$	282,358
Gross profit	$	99,199		$	—		$	(13,461	)	$	85,738
Gross margin	35.1		%	—		%	—		%	30.4		%
Operating income (loss)	$	39,964		$	—		$	(44,067	)	$	(4,103	)

Summary of Revenue by Country

The following table summarizes revenue, by geographic region, as a percentage of total revenues based upon ship-to location:



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
United States	33.3	%	23.4	%	28.1	%
South Korea	17.1		25.2		19.6
Taiwan	14.9		21.9		18.4
Europe	12.9		9.0		11.4
Asia-Pacific (1)	11.4		11.1		12.9
Japan	10.0		9.4		9.6
Rest of the world	0.4		—		—
Total Revenues	100.0	%	100.0	%	100.0	%

(1) Asia-Pacific includes all countries in the region except Taiwan, Japan and South Korea, which are disclosed separately.

Summary of Revenue by Product Group

The following table summarizes revenue by product group (in thousands):



	Fiscal Years Ended
	December 31, 2016		December 26, 2015		December 27, 2014
Foundry & Logic	$	237,591	$	145,839	$	142,360
DRAM	86,910		125,512		110,800
Flash	13,469		11,007		15,370
Systems	45,911		—		—
Total revenues	$	383,881	$	282,358	$	268,530

Schedule of Major Customers With Revenues Greater Than 10%

The following customers represented greater than 10% of our revenues in fiscal 2016, fiscal 2015 and fiscal 2014:



	Fiscal 2016		Fiscal 2015		Fiscal 2014
Intel	30.1	%	19.6	%	19.7	%
Samsung	*		14.6		*
SK hynix	*		14.3		16.9
Micron	*		11.7		15.0
Total revenues attributable to customers greater than 10%	30.1	%	60.2	%	51.6	%

* Less than 10% of revenues

Long-lived Assets by Geographic Areas

Long-lived assets, comprising of net property, plant and equipment, goodwill and net intangibles assets are reported

based on the location of the asset. Long-lived assets by geographic location are as follows (in thousands):



	December 31, 2016		December 26, 2015
United States	$	323,369	$	77,257
Europe	30,903		655
Asia-Pacific (1)	1,709		689
South Korea	733		1,128
Japan	510		295
Singapore	57		112
Total	$	357,281	$	80,136

(1) Asia-Pacific includes all countries in the region except Taiwan, Japan and South Korea, which are disclosed separately.

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The results of operations for any quarter are not necessarily indicative of the results to be expected for any future period.



	Fiscal Quarters Ended
	Dec. 31, 2016 (3)			Sep. 24, 2016			June. 25, 2016 (1) (2)			March 26, 2016			Dec. 26, 2015			Sep. 26, 2015 (5)			June. 27, 2015		March 28, 2015 (4)
	(in thousands, except per share data)
Revenues	$	123,888		$	123,299		$	83,083		$	53,611		$	71,782		$	65,862		$	73,885	$	70,829
Cost of revenues	83,613			96,111			57,656			43,819			50,591			47,407			50,582		48,040
Gross profit	40,275			27,188			25,427			9,792			21,191			18,455			23,303		22,789
Operating Expenses:
Research and development	18,218			17,253			11,133			10,849			11,236			10,645			11,217		11,086
Selling, general and administrative	23,890			23,008			14,030			12,516			10,719			11,108			11,381		11,882
Restructuring and impairment charges, net	12,697			85			6,910			—			(3		)	59			8		503
Total operating expenses	54,805			40,346			32,073			23,365			21,952			21,812			22,606		23,471
Operating income (loss)	(14,530		)	(13,158		)	(6,646		)	(13,573		)	(761		)	(3,357		)	697		(682		)
Interest income, net	59			52			88			117			70			65			65		85
Other income (expense), net	(946		)	(1,042		)	(302		)	(314		)	(36		)	982			100		1,501
Income (loss) before income taxes	(15,417		)	(14,148		)	(6,860		)	(13,770		)	(727		)	(2,310		)	862		904
Provision (benefit) for income taxes	26			50			(43,744		)	30			(108		)	215			24		121
Net income (loss)	$	(15,443	)	$	(14,198	)	$	36,884		$	(13,800	)	$	(619	)	$	(2,525	)	$	838	$	783
Net income (loss) per share:
Basic	$	(0.22	)	$	(0.20	)	$	0.62		$	(0.24	)	$	(0.01	)	$	(0.04	)	$	0.01	$	0.01
Diluted	$	(0.22	)	$	(0.20	)	$	0.61		$	(0.24	)	$	(0.01	)	$	(0.04	)	$	0.01	$	0.01
Weighted average number of shares used in per share calculations:
Basic	70,807			70,502			59,572			58,431			58,128			58,209			58,109		56,594
Diluted	70,807			70,502			59,988			58,431			58,128			58,209			59,094		58,838

(1)


(2)	In the second quarter of fiscal 2016, we recorded an income tax benefit of $43.7 million primarily due to the release of valuation allowance of our deferred tax assets in connection with our acquisition of Cascade Microtech. See Note 14, Income Taxes, to the Notes to Consolidated Financial Statements for further details.


(3)	In the fourth quarter of fiscal 2016, we recorded an impairment charge of $12.4 million relating to an in-process research and development intangible asset acquired as part of our acquisition of Cascade Microtech. See Note 7, Impairment of Long-lived Assets, to the Notes to Consolidated Financial Statements for further details.


(4)	In the first quarter of fiscal 2015, we recorded a $1.5 million gain from a business interruption insurance claim relating to a factory fire at a customer. See Note 18, Business Interruption Insurance Claim Recovery, to the Notes to Consolidated Financial Statements for further details.


(5)	In the third quarter of fiscal 2015, we recorded a $1.0 million net gain from the sale of intellectual property.

Formation and Business of the Company (Details)	3 Months Ended				12 Months Ended
Formation and Business of the Company (Details)	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of days in fiscal year	98 days	91 days	91 days	91 days	371 days	364 days	364 days

Summary of Significant Accounting Policies - Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 26, 2015
Accounting Policies [Abstract]
Restricted cash	$ 1.2	$ 0.4

Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Accounting Policies [Abstract]
Aggregate inventory write downs	$ 6,631	$ 6,493	$ 7,127

Summary of Significant Accounting Policies - Property, Plant, and Equipment (Details)	12 Months Ended
	Dec. 31, 2016
Machinery & Equipment
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years
Machinery & Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Computer equipment & Software \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Computer equipment & Software \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years
Furniture & Fixtures \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Furniture & Fixtures \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years

Summary of Significant Accounting Policies - Goodwill (Details)			12 Months Ended
	Jun. 24, 2016 segment	Jun. 23, 2016 segment	Dec. 31, 2016 unit	Dec. 26, 2015 unit
Goodwill and Intangible Assets Disclosure [Abstract]
Number of reporting units \| unit			4	1
Number of reportable segments	2	1
Number of operating segments	3	1

Summary of Significant Accounting Policies - Intangibles (Details)	12 Months Ended
	Dec. 31, 2016
Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset weighted average useful life	1 year
Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible asset weighted average useful life	10 years

Summary of Significant Accounting Policies - Concentration of Credit Risk and Other Risks and Uncertainties (Details) - Customer Concentration Risk - Customer	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	30.10%	60.20%	51.60%
Accounts Receivable
Concentration Risk [Line Items]
Number of major customers	1
Intel \| Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	30.10%	19.60%	19.70%
Samsung \| Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%		14.60%
SK hynix \| Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%		14.30%	16.90%
Micron \| Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%		11.70%	15.00%
Major Customer 1 \| Accounts Receivable
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	21.00%	29.00%

Summary of Significant Accounting Policies - Revenue Recognition (Details)	12 Months Ended
	Dec. 31, 2016
Minimum
Deferred Revenue Arrangement [Line Items]
Revenue recognition period	1 year
Maximum
Deferred Revenue Arrangement [Line Items]
Revenue recognition period	2 years

Summary of Significant Accounting Policies - Warranty Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty Accrual beginning balance	$ 1,116	$ 1,592
Warranty reserve from acquisition-Cascade Microtech	795	0
Accruals	5,254	2,536
Settlements	(4,193)	(3,012)
Warranty Accrual ending balance	$ 2,972	$ 1,116

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at Beginning of Year	$ 284	$ 266	$ 265
Additions	62	20	5
Reductions	(48)	(2)	(4)
Balance at End of Year	$ 298	$ 284	$ 266

Summary of Significant Accounting Policies - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended									12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Mar. 29, 2014	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Restructuring and Related Activities [Abstract]
Restructuring charges	$ 12,697	$ 85	$ 6,910	$ 0	$ (3)	$ 59	$ 8	$ 503	$ 2,000	$ 7,288	$ 559	$ 2,668

Summary of Significant Accounting Policies - Net Loss per Share (Details) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Accounting Policies [Abstract]
Net loss used in computing basic and diluted net loss per share	$ (15,443)	$ (14,198)	$ 36,884	$ (13,800)	$ (619)	$ (2,525)	$ 838	$ 783	$ (6,557)	$ (1,523)	$ (19,185)
Weighted-average shares used in computing basic net loss per share (in shares)	70,807	70,502	59,572	58,431	58,128	58,209	58,109	56,594	64,941	57,850	55,908
Add potentially dilutive securities (in shares)									0	0	0
Weighted-average shares used in computing basic and diluted net loss per share (in shares)									64,941	57,850	55,908

Summary of Significant Accounting Policies - Net Loss Per Share Weighted-Average Dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	5,321	4,906	2,902
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	2,198	2,320	2,874
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	3,113	2,578	0
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	10	8	28

Summary of Significant Accounting Policies - Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Accounting Policies [Abstract]
Tax on marketable securities	$ 364	$ 428
Unrealized loss on marketable securities, net of tax of $364 in fiscal 2016 and $428 in fiscal 2015, respectively	(454)	(483)
Cumulative translation adjustments	(3,781)	(1,739)
Unrealized gains on derivative instruments	495	0
Accumulated other comprehensive loss	$ (3,740)	$ (2,222)

Balance Sheet Components - Marketable Securities (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Available-for-sale Securities [Abstract]
Amortized Cost	$ 7,504,000	$ 41,380,000
Available-for-sale Securities, Gross Unrealized Gains	0	1,000
Available-for-sale Securities, Gross Unrealized Losses	(7,000)	(56,000)
Available-for-sale Securities Fair Value	$ 7,497,000	41,325,000
Maximum maturity	3 years
Continuous loss position of investments	$ 0	0
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Due in one year or less - Amortized Cost	7,504,000	33,882,000
Due in one year to five years - Amortized Cost	0	7,498,000
Amortized Cost	7,504,000	41,380,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Due in one year or less - Fair Value	7,497,000	33,871,000
Due in one year to five years - Fair Value	0	7,454,000
Available-for-sale Securities Fair Value	7,497,000	41,325,000
U.S. Treasuries
Available-for-sale Securities [Abstract]
Amortized Cost	7,504,000	18,896,000
Available-for-sale Securities, Gross Unrealized Gains	0	1,000
Available-for-sale Securities, Gross Unrealized Losses	(7,000)	(44,000)
Available-for-sale Securities Fair Value	7,497,000	18,853,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost	7,504,000	18,896,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Available-for-sale Securities Fair Value	$ 7,497,000	18,853,000
Agency securities (Federal)
Available-for-sale Securities [Abstract]
Amortized Cost		22,484,000
Available-for-sale Securities, Gross Unrealized Gains		0
Available-for-sale Securities, Gross Unrealized Losses		(12,000)
Available-for-sale Securities Fair Value		22,472,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Amortized Cost		22,484,000
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract]
Available-for-sale Securities Fair Value		$ 22,472,000

Balance Sheet Components - Asset Retirement Obligation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation beginning balance	$ 919	$ 903
Initial amount recorded for new asset retirement obligation	34	10
Initial amount recorded for new asset retirement obligation upon acquisition of Cascade Microtech	165	0
Currency translation	11	6
Asset retirement obligation ending balance	1,129	919
Other accrued liabilities, current
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation beginning balance	212
Asset retirement obligation ending balance	165	212
Deferred rent and other liabilities, non-current
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Asset retirement obligation beginning balance	707
Asset retirement obligation ending balance	$ 964	$ 707

Balance Sheet Components - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015
Balance Sheet Components [Abstract]
Raw materials	$ 27,402	$ 12,996
Work-in-progress	20,390	12,492
Finished goods	12,014	1,735
Inventory, Net	$ 59,806	$ 27,223

Balance Sheet Components - Property Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 278,710	$ 251,435
Less: Accumulated depreciation and amortization	(241,943)	(232,005)
Net long-lived assets	36,767	19,430
Construction-in-progress	5,896	4,423
Property, plant and equipment, net	42,663	23,853
Fully depreciated assets	1,700	1,600
Impairment of long-lived assets	12,400	8	$ 1,028
Depreciation, excluding impairments	11,300	10,600	$ 11,700
Machinery & Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	169,056	150,983
Computer equipment & Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	30,640	27,951
Furniture & Fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,060	5,380
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 72,954	$ 67,121

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 16,516	$ 12,286
Accrued indirect and other taxes	3,634	2,189
Accrued commissions	792	366
Accrued warranty	2,972	1,116
Deferred rent	160	325
Accrued restructuring	434	2
Other accrued expenses	5,676	5,223
Total	$ 30,184	$ 21,507

Acquisition - Additional Information (Details)		3 Months Ended	12 Months Ended
Acquisition - Additional Information (Details)	Jun. 24, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Business Acquisition [Line Items]
Fair value of stock issued in connection with the acquisition of Cascade Microtech			$ 97,080,000	$ 0	$ 0
Impairment of long-lived assets			12,400,000	8,000	$ 1,028,000
Deferred Tax Asset Valuation Allowance
Business Acquisition [Line Items]
Increases (decreases) to pro-forma net income				44,000,000
Acquisition-related Transaction Costs
Business Acquisition [Line Items]
Increases (decreases) to pro-forma net income				(14,400,000)
Restructuring Charges
Business Acquisition [Line Items]
Increases (decreases) to pro-forma net income				(7,300,000)
Cascade Microtech
Business Acquisition [Line Items]
Cash paid to acquire business (In USD per share) \| $ / shares	$ 16.00
Fraction of parent shares issued per share of acquiree (ratio)	0.6534
Total acquisition consideration	$ 325,100,000
Cash acquired in combination	$ 40,700,000	$ 40,681,000	40,681,000
Total stock issued to acquire business (in shares) \| shares	10,450,189
Market value of hares issued in acquisition, amount	$ 93,200,000
Transaction costs related to acquisition			6,500,000
Adjustment to intangible assets			(100,000)
Adjustment to accrued liabilities			500,000
Net increase in goodwill			400,000
Impairment of long-lived assets		$ 12,400,000
Increases (decreases) to pro-forma net income			$ (20,641,000)	$ (15,469,000)
Cascade Microtech \| In Process Research and Development
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired	12,400,000
Cascade Microtech \| Developed technologies
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	91,100,000
Cascade Microtech \| Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	23,053,000
Cascade Microtech \| Trade name
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	7,600,000
Cascade Microtech \| Senior Secured Term Loan
Business Acquisition [Line Items]
Senior secured loan to finance merger	150,000,000
Cascade Microtech \| Common Stock
Business Acquisition [Line Items]
Fair value of stock issued in connection with the acquisition of Cascade Microtech	$ 3,900,000
Cascade Microtech \| FormFactor
Business Acquisition [Line Items]
Closing stock price (in USD per share) \| $ / shares	$ 8.92
Cascade Microtech \| Former Shareholders of Cascade Microtech
Business Acquisition [Line Items]
Cash paid in acquisition	$ 255,900,000
Cascade Microtech \| Vested Equity Award Holders
Business Acquisition [Line Items]
Cash paid in acquisition	$ 12,800,000
Cascade Microtech \| Restricted Stock Units
Business Acquisition [Line Items]
Amount over exercise price for shares converted in acquisition (in USD per share) \| $ / shares	$ 21.47
Equity awards granted during period (in shares) \| shares	777,444
Cascade Microtech \| Stock Options
Business Acquisition [Line Items]
Amount over exercise price for shares converted in acquisition (in USD per share) \| $ / shares	$ 21.47
Options granted during the period (in shares) \| shares	152,276

Acquisition - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Jun. 24, 2016	Dec. 26, 2015	Dec. 27, 2014
Business Acquisition [Line Items]
Goodwill	$ 188,010		$ 30,731	$ 30,731
Cascade Microtech
Business Acquisition [Line Items]
Cash and cash equivalents	40,681	$ 40,700
Accounts receivable	27,112
Inventory	38,315
Prepaid expenses and other current assets	6,249
Property, plant and equipment	19,875
Other long-term assets	818
Deferred revenue	(1,829)
Accounts payable and accrued liabilities	(23,370)
Deferred tax liabilities	(48,993)
Other long-term liabilities	(960)
Total tangible assets acquired and liabilities assumed	57,898
Intangible assets	149,753	$ 149,753
Goodwill	158,141
Total acquisition price	$ 365,792

Acquisition - Intangible Assets Acquired (Details) - USD ($) $ in Thousands		12 Months Ended
	Jun. 24, 2016	Dec. 31, 2016
Cascade Microtech
Business Acquisition [Line Items]
Total intangible assets	$ 149,753	$ 149,753
In Process Research and Development \| Cascade Microtech
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired	12,400
Developed technologies \| Cascade Microtech
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 91,100
Intangible asset weighted average useful life	4 years 8 months 6 days
Customer relationships
Business Acquisition [Line Items]
Intangible asset weighted average useful life		5 years 9 months 6 days
Customer relationships \| Cascade Microtech
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 23,053
Intangible asset weighted average useful life	6 years 9 months 6 days
Backlog
Business Acquisition [Line Items]
Intangible asset weighted average useful life		2 months 6 days
Backlog \| Cascade Microtech
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 15,600
Intangible asset weighted average useful life	6 months 6 days
Trade name
Business Acquisition [Line Items]
Intangible asset weighted average useful life		4 years 6 days
Trade name \| Cascade Microtech
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 7,600
Intangible asset weighted average useful life	3 years 6 months 6 days

Acquisition - Pro Forma Information (Details) - Cascade Microtech - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Business Acquisition [Line Items]
Revenues	$ 455,713	$ 426,336
Net loss	$ (20,641)	$ (15,469)
Net loss per share - basic (in dollars per share)	$ (0.27)	$ (0.23)
Net loss per share - diluted (in dollars per share)	$ (0.27)	$ (0.23)

Debt - Schedule of Debt (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Debt Disclosure [Abstract]
Senior secured term loan	$ 139,375
Less debt issuance costs	(1,199)
Total	$ 138,176

Debt - Additional Information (Details)	Jun. 30, 2016	Jun. 24, 2016 USD ($)
Debt Instrument [Line Items]
Debt to earnings ratio, in year one	2.75
Debt to earnings ratio, in year two	2.50
Minimum fixed charge coverage ratio in years one and two	1.50
Minimum fixed charge coverage ratio in year three	1.30
Minimum fixed charge coverage ratio, in year four and thereafter	1.20
Senior Secured Term Loan
Debt Instrument [Line Items]
Interest payment term		5 years
Debt principal payable in current year, percentage	5.00%
Debt principal payable in year two, percentage	10.00%
Debt principal payable in year three, percentage	20.00%
Debt principal payable in year four, percentage	30.00%
Debt principal payable in year five, percentage	35.00%
Senior Secured Term Loan \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		2.00%
Senior Secured Term Loan \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate		1.00%
Senior Secured Term Loan \| Cascade Microtech
Debt Instrument [Line Items]
Senior secured loan to finance merger		$ 150,000,000

Restructuring Charges - Additional Information (Details) $ in Thousands		3 Months Ended									9 Months Ended	12 Months Ended
	Jan. 27, 2014 Employee positions	Dec. 31, 2016 USD ($)	Sep. 24, 2016 USD ($)	Jun. 25, 2016 USD ($)	Mar. 26, 2016 USD ($)	Dec. 26, 2015 USD ($)	Sep. 26, 2015 USD ($)	Jun. 27, 2015 USD ($)	Mar. 28, 2015 USD ($)	Mar. 29, 2014 USD ($)	Dec. 27, 2014 USD ($) positions	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 12,697	$ 85	$ 6,910	$ 0	$ (3)	$ 59	$ 8	$ 503	$ 2,000		$ 7,288	$ 559	$ 2,668
Restructuring and impairment charges, net												19,692	567	3,887
Restructuring costs, positions eliminated \| Employee	52
Restructuring costs, additional positions eliminated \| positions	9										5
Employee Severance and Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges										1,400	$ 700	6,220	59	2,068
Employee Severance and Benefits \| Cascade Microtech
Restructuring Cost and Reserve [Line Items]
Restructuring charges				5,400								5,400
Share-based Compensation Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges												964	0	0
Share-based Compensation Expense \| Cascade Microtech
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 700								700
Cease Use Charges
Restructuring Cost and Reserve [Line Items]
Restructuring charges												100
Property and Equipment Impairment
Restructuring Cost and Reserve [Line Items]
Restructuring charges												0	0	$ 600
Impairment charges										$ 600
FormFactor \| Employee Severance and Benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges												800
FormFactor \| Share-based Compensation Expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges												$ 300	$ 500

Restructuring Charges - Restructuring Activities (Details) - USD ($) $ in Thousands	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Mar. 29, 2014	Dec. 27, 2014	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 2				$ 584	$ 138		$ 2	$ 584	$ 138
Restructuring charges	$ 12,697	$ 85	$ 6,910	0	$ (3)	$ 59	$ 8	503	2,000		7,288	559	2,668
Asset impairments													(600)
Cash payments											(5,892)	(641)	(1,620)
Non-cash settlements											(964)	(500)	(2)
Restructuring reserve, ending balance	434				2					$ 584	434	2	584
Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				2				584	138		2	584	138
Restructuring charges									1,400	700	6,220	59	2,068
Asset impairments													0
Cash payments											(5,892)	(641)	(1,620)
Non-cash settlements											0	0	(2)
Restructuring reserve, ending balance	330				2					584	330	2	584
Property and Equipment Impairment
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				0				0	0		0	0	0
Restructuring charges											0	0	600
Asset impairments													(600)
Cash payments											0	0	0
Non-cash settlements											0	0	0
Restructuring reserve, ending balance	0				0					0	0	0	0
Contract Termination and Other Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				0				0	0		0	0	0
Restructuring charges											104	500	0
Asset impairments													0
Cash payments											0	0	0
Non-cash settlements												(500)	0
Restructuring reserve, ending balance	104				0					0	104	0	0
Stock-based Compensation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 0				$ 0	$ 0		0	0	0
Restructuring charges											964	0	0
Asset impairments													0
Cash payments											0	0	0
Non-cash settlements											(964)	0	0
Restructuring reserve, ending balance	$ 0				$ 0					$ 0	$ 0	$ 0	$ 0

Impairment of Long-lived Assets - Impairment of Long-lived Assets (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Impairment of long-lived assets:
Assets held for sale	$ 0	$ 0	$ 191,000
Assets to be disposed of other than by sale	12,400,000	8,000	1,028,000
Total	$ 12,400,000	$ 8,000	$ 1,219,000

Impairment of Long-lived Assets - Assets Held for Sale (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Long Lived Assets Held-for-sale [Line Items]
Impairment of assets held for sale	$ 0	$ 0	$ 191,000
Long-lived assets classified as held for sale	0	0	0
Impairment of long-lived assets	12,400,000	8,000	1,219,000
Gain on sale of property and equipment	(361,000)	1,009,000	10,000
Impairment of long-lived assets	$ 12,400,000	$ 8,000	1,219,000
Assets previously held for sale
Long Lived Assets Held-for-sale [Line Items]
Impairment of long-lived assets			200,000
Building
Long Lived Assets Held-for-sale [Line Items]
Impairment of long-lived assets			600,000
Gain on sale of property and equipment			200,000
Machinery & Equipment
Long Lived Assets Held-for-sale [Line Items]
Impairment of long-lived assets			500,000
Gain on sale of property and equipment			$ 52,000

Impairment of Long-lived Assets - Assets to Be Disposed of Other Than Sale (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Property, Plant and Equipment Impairment or Disposal [Abstract]
Assets to be disposed of other than by sale	$ 12,400	$ 8	$ 1,028

Derivative Financial Instruments - Foreign Currency Derivatives (Details) - Not Designated as Hedging Instrument - Foreign Exchange Forward € in Thousands, ₩ in Thousands, ¥ in Thousands, $ in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)	Dec. 31, 2016 KRW (₩)	Dec. 31, 2016 TWD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2016 JPY (¥)
Derivatives, Fair Value [Line Items]
Total USD notional amount of outstanding foreign exchange contracts	$ 29,660
Other income (expense), net
Derivatives, Fair Value [Line Items]
Foreign exchange forward contracts	139	$ (310)
Buy \| Taiwan Dollar
Derivatives, Fair Value [Line Items]
Derivative liability contract amount	(1,326)			$ (42,660)
Buy \| Korean Won
Derivatives, Fair Value [Line Items]
Derivative liability contract amount	(1,508)		₩ (1,806,386)
Buy \| Euro
Derivatives, Fair Value [Line Items]
Derivative liability contract amount	(2,774)				€ (2,500)
Sell \| Euro
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	2,876				2,732
Sell \| Japanese Yen
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	13,252					¥ 1,548,535
Sell \| Euro
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	17,852				€ 15,877
Sell \| Japanese Yen
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	$ 1,288					¥ 136,000

Derivative Financial Instruments - Interest Rate Swaps (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Hedge ineffectiveness	$ 51
Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)	628	$ 0
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(160)	0
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )	51	0
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset	838
Interest Rate Swap \| Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset	(800)
Interest Rate Swap \| Designated as Hedging Instrument \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)	628	0
Interest Rate Swap \| Other income (expense), net \| Designated as Hedging Instrument \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	(160)	0
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )	$ 51	$ 0

Fair Value (Details) - USD ($)	Dec. 31, 2016	Dec. 26, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	$ 7,497,000	$ 41,325,000
Total	28,822,000	124,260,000
Assets measured at fair value		0
Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	1,137,000
Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	838,000
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	19,350,000	82,935,000
U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	7,497,000	18,853,000
Agency securities (Federal)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities		22,472,000
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	19,350,000	82,935,000
Level 1 \| Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0
Level 1 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	$ 0
Level 1 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Net asset value (in USD per share)	$ 1
Cash equivalents	$ 19,350,000	82,935,000
Level 1 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0	0
Level 1 \| Agency securities (Federal)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities		0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total	9,472,000	41,325,000
Level 2 \| Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	1,137,000
Level 2 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	838,000
Level 2 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Level 2 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	$ 7,497,000	18,853,000
Level 2 \| Agency securities (Federal)
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities		$ 22,472,000

Goodwill and Intangible Assets - Goodwill (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	$ 188,010	$ 30,731	$ 30,731
Cascade Microtech
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	158,141
MicroProbe Inc.
Business Combination, Separately Recognized Transactions [Line Items]
Goodwill	$ 30,700	$ 30,700

Goodwill and Intangible Assets - Finite and Indefinite-lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross Amount, Beginning balance		$ 73,588
Finite-lived Intangible Assets, Additions/Disposals		136,484
Intangible Assets, Gross Amount, Ending balance	$ 210,072	210,072	$ 73,588
Accumulated Amortization, Beginning balance		48,036
Expense, net		35,427	13,100	$ 18,800
Accumulated Amortization, Ending balance	83,463	83,463	48,036
Intangible Assets, Net	126,608	126,608	25,552
Intangible Assets Net Excluding Goodwill [Roll Forward]
Intangible Assets, Gross Amount, After Addition, Beginning balance		73,588
Intangible Assets, Gross Amount, Additions		148,884
Intangible Assets, Gross Amount, After Addition, Ending balance	222,472	222,472	73,588
Intangible Assets, Gross Amount, Beginning balance		73,588
Intangible Assets, Gross Amount, Additions		136,484
Intangible Assets, Gross Amount, Beginning balance	210,072	210,072	73,588
Intangible Assets, Net	139,008	139,008	25,552
Total Intangible Assets, Net	126,608	126,608	25,552
In Process Research and Development
Indefinite-lived Intangible Assets [Roll Forward]
Indefinite-lived Intangible Assets, Beginning balance		0
Indefinite-lived Intangible Assets, Additions/Disposals		12,400
Indefinite-lived Intangible Assets, Ending balance	12,400	12,400	0
In Process Research and Development \| Intangible Assets Disposed of by Sale
Indefinite-lived Intangible Assets [Roll Forward]
Indefinite-lived Intangible Assets, Beginning balance		0
Indefinite-lived Intangible Assets, Additions/Disposals		(12,400)
Indefinite-lived Intangible Assets, Ending balance	(12,400)	(12,400)	0
Existing developed technologies
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross Amount, Beginning balance		52,200
Finite-lived Intangible Assets, Additions/Disposals		90,501
Intangible Assets, Gross Amount, Ending balance	142,701	142,701	52,200
Accumulated Amortization, Beginning balance		39,581
Expense, net		16,550
Accumulated Amortization, Ending balance	56,131	56,131	39,581
Intangible Assets, Net	86,569	$ 86,569	12,619
Weight Average Useful Life		4 years 4 months 8 days
Existing developed technologies \| Intangible Assets Disposed of by Sale
Finite-lived Intangible Assets [Roll Forward]
Finite-lived Intangible Assets, Additions/Disposals	12,400
Trade name
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross Amount, Beginning balance		$ 4,388
Finite-lived Intangible Assets, Additions/Disposals		7,533
Intangible Assets, Gross Amount, Ending balance	11,921	11,921	4,388
Accumulated Amortization, Beginning balance		1,409
Expense, net		1,580
Accumulated Amortization, Ending balance	2,989	2,989	1,409
Intangible Assets, Net	8,932	$ 8,932	2,979
Weight Average Useful Life		4 years 6 days
Customer relationships
Finite-lived Intangible Assets [Roll Forward]
Intangible Assets, Gross Amount, Beginning balance		$ 17,000
Finite-lived Intangible Assets, Additions/Disposals		22,869
Intangible Assets, Gross Amount, Ending balance	39,869	39,869	17,000
Accumulated Amortization, Beginning balance		7,046
Expense, net		3,808
Accumulated Amortization, Ending balance	10,854	10,854	7,046
Intangible Assets, Net	29,015	$ 29,015	$ 9,954
Weight Average Useful Life		5 years 9 months 6 days
Backlog
Finite-lived Intangible Assets [Roll Forward]
Finite-lived Intangible Assets, Additions/Disposals		$ 15,581
Intangible Assets, Gross Amount, Ending balance	15,581	15,581
Expense, net		13,489
Accumulated Amortization, Ending balance	13,489	13,489
Intangible Assets, Net	$ 2,092	$ 2,092
Weight Average Useful Life		2 months 6 days

Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 35,427	$ 13,100	$ 18,800
Finite-Lived Intangible Assets, Net, Amortization Expense, Rolling Maturity [Abstract]
2017	30,672
2018	28,303
2019	25,639
2020	23,570
2021	12,915
and thereafter	5,509
Total	126,608
Intellectual Property \| Cost of Sales
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	30,000	10,400	16,100
Intellectual Property \| Selling, General and Administrative Expenses
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 5,400	$ 2,700	$ 2,700

Goodwill and Intangible Assets - Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 27, 2014
Goodwill [Line Items]
Goodwill, 2014 balance	$ 30,731	$ 30,731
Goodwill, beginning balance	30,731
Additions-Cascade Microtech	158,141
Foreign currency translation	(862)
Goodwill, ending balance	188,010
Probe Cards
Goodwill [Line Items]
Goodwill, 2014 balance	30,731	30,731
Goodwill, beginning balance	30,731
Additions-Cascade Microtech	141,751
Foreign currency translation	0
Goodwill, ending balance	172,482
Systems
Goodwill [Line Items]
Goodwill, 2014 balance	0	$ 0
Goodwill, beginning balance	0
Additions-Cascade Microtech	16,390
Foreign currency translation	(862)
Goodwill, ending balance	$ 15,528

Commitments and Contingencies - Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 6.5	$ 4.9	$ 4.8

Commitments and Contingencies - Operating Leases (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2017	$ 6,279
2018	5,789
2019	4,882
2020	3,581
2021	3,236
Thereafter	15,734
Total	$ 39,501

Commitments and Contingencies - Other Contractual Obligations (Details) - USD ($)	Dec. 31, 2016	Jun. 24, 2016	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Purchase obligations
2017	$ 33,696,000
2018	4,550,000
2019	515,000
2020	0
2021	0
Total	38,761,000
Senior secured term loan facility-principal payments
2017	13,125,000
2018	26,250,000
2019	41,250,000
2020	50,625,000
2021	8,125,000
Total	139,375,000
Senior secured term loan facility-interest payments
2017	2,828,000
2018	2,400,000
2019	1,739,000
2020	821,000
2021	41,000
Total	7,829,000
Total
2017	49,649,000
2018	33,200,000
2019	43,504,000
2020	51,446,000
2021	8,166,000
Total	$ 185,965,000
Debt Instrument [Line Items]
Effective interest rate on commitments	2.00%
Unrecognized tax benefits	$ 17,978,000		$ 17,033,000	$ 16,333,000	$ 16,972,000
Cascade Microtech \| Senior Secured Term Loan
Debt Instrument [Line Items]
Senior secured loan to finance merger		$ 150,000,000

Commitments and Contingencies - Legal Matters (Details) - USD ($) $ in Millions	Mar. 03, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Accrual for potential settlement payment		$ 1.5
Subsequent Event
Loss Contingencies [Line Items]
Amount of settlement	$ 1.5

Stockholders' Equity - Preferred Stock (Details) - $ / shares	Dec. 31, 2016	Dec. 26, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock authorized (in shares)	10,000,000	10,000,000
Preferred stock par value (in USD per share)	$ 0.001	$ 0.001
Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred stock authorized (in shares)	10,000,000
Preferred stock par value (in USD per share)	$ 0.001

Stockholders' Equity - Common Stock (Details) - USD ($)	12 Months Ended
Stockholders' Equity - Common Stock (Details) - USD ($)	Dec. 31, 2016	Dec. 26, 2015	Feb. 28, 2017	Apr. 16, 2015
Class of Stock [Line Items]
Dividends declared and paid	$ 0
Stock repurchased during the period, amount	$ (97,079,000)	$ 8,211,000
Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount				$ 25,000,000.0
Stock repurchased during the period (in shares)		1,013,162
Stock repurchased during the period, amount		$ 8,200,000
Subsequent Event \| Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount			$ 25,000,000

Stockholders' Equity - Equity Incentive Plans (Details) - Equity Incentive Plan - shares	12 Months Ended
	Dec. 31, 2016	May 01, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total amount of shares authorized (in shares)		4,500,000.0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	3 years
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	4 years
Restricted stock conversion rate (in shares)		1.70
Term of options granted	7 years
Shares available for grant (in shares)	3,500,000.0
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	4 years

Stockholders' Equity - Stock Options (Details) - USD ($)			12 Months Ended
	Jun. 24, 2016	Feb. 09, 2015	Dec. 31, 2016
Equity Incentive Plan
Number of Shares
Number of Shares, Outstanding (in shares)			2,320,195
Number of Shares, Options exercised (in shares)			(232,190)
Number of Shares, Options canceled (in shares)			(42,250)
Number of Shares, Outstanding (in shares)			2,198,031
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding (in USD per share)			$ 9.40
Weighted Average Exercise Price, Options granted (in USD per share)			4.42
Weighted Average Exercise Price, Options exercised (in USD per share)			8.63
Weighted Average Exercise Price, Options canceled (in USD per share)			9.87
Weighted Average Exercise Price, Outstanding (in USD per share)			$ 9.13
Vested and Expected to Vest
Number of Shares, Vested and expected to vest (in shares)			2,171,229
Weighted Average Exercise Price, Vested and expected to vest (in USD per share)			$ 9.14
Weighted Average Remaining Contractual Life, Vested and expected to vest			1 year 11 months 18 days
Aggregate Intrinsic Value, Vested and expected to vest			$ 4,735,512
Additional Disclosures
Number of Shares, Exercisable (in shares)			1,767,871
Weighted Average Exercise Price, Exercisable (in USD per share)			$ 9.48
Weighted Average Remaining Contractual Life, Outstanding			2 years 6 days
Aggregate Intrinsic Value, Outstanding			$ 4,825,647
Weighted Average Remaining Contractual Life, Exercisable			1 year 1 month 20 days
Aggregate Intrinsic Value, Exercisable			$ 3,305,020
Stock Options \| Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 1,700,000
Additional Disclosures
Stock options granted (in shares)		450,000
Stock Options \| Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted during the period (in shares)			152,276
Number of Shares
Number of Shares, Options granted (in shares)			152,276
Cascade Microtech \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted during the period (in shares)	152,276
Total grant date fair value of options granted	$ 800,000
Stock-based compensation expense	$ 300,000
Number of Shares
Number of Shares, Options granted (in shares)	152,276

Stockholders' Equity - Weighted Average Assumptions (Details)	12 Months Ended
	Dec. 31, 2016
Equity [Abstract]
Dividend yield	0.00%
Expected volatility	47.50%
Risk-free interest rate	1.60%
Expected term (in years)	5 years 6 months 6 days

Stockholders' Equity - Restricted Stock Units (Details) - Restricted Stock Units $ / shares in Units, $ in Millions						12 Months Ended
	Aug. 19, 2016 USD ($) executive shares	Jun. 24, 2016 USD ($) shares	May 02, 2016 USD ($) shares	May 28, 2015 USD ($) executive shares	May 05, 2015 shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 26, 2015 USD ($) $ / shares shares	Dec. 27, 2014 USD ($) $ / shares shares	May 05, 2014 executive
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Stock options granted (in shares)	155,000			195,000	350,000
Number of recipients (executives) \| executive	6			7					7
Stock-based compensation expense \| $	$ 1.7		$ 0.3	$ 1.5
Stock issued during the period for equity awards (in shares)			40,000
Fair value of restricted stock units vested during the period \| $						$ 12.0	$ 18.1	$ 8.2
Cascade Microtech
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Equity awards granted during period (in shares)		777,444
Total grant date fair value \| $		$ 6.9
Total grant date fair value, unvested units \| $		$ 3.6
Equity Incentive Plan
Number of Shares
Number of Shares, Restricted stock units, beginning balance (in shares)						2,578,138	3,250,046	2,929,639
Number of Shares, Granted (in shares)						2,296,210	1,540,250	1,900,000
Number of Shares, Vested (in shares)						(1,579,218)	(1,993,603)	(1,282,442)
Number of Shares, Canceled (in shares)						(182,509)	(218,555)	(297,151)
Number of Shares, Restricted stock units, ending balance (in shares)						3,112,621	2,578,138	3,250,046
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Weighted Average Grant Date Fair Value, Restricted stock units, beginning balance (in USD per share) \| $ / shares						$ 7.63	$ 6.07	$ 5.88
Weighted Average Grant Date Fair Value, Granted (in USD per share) \| $ / shares						8.20	8.64	6.52
Weighted Average Grant Date Fair Value, Vested (in USD per share) \| $ / shares						6.60	6.00	6.30
Weighted Average Grant Date Fair Value, Canceled (in USD per share) \| $ / shares						6.44	6.36	6.17
Weighted Average Grant Date Fair Value, Restricted stock units, ending balance(in USD per share) \| $ / shares						$ 8.65	$ 7.63	$ 6.07

Stockholders' Equity - Employee Stock Purchase Plan (Details)	12 Months Ended
	Dec. 31, 2016 purchase_period $ / shares shares	Dec. 26, 2015 $ / shares shares	Dec. 27, 2014 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount from market price, offering date	85.00%
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of purchase periods, 12 months offering period	2
Number of purchase periods, 6 months offering period	1
Issuance of common stock under the Employee Stock Purchase Plan (in shares) \| shares	557,281	565,493	586,386
Weighted average exercise price, exercisable (in USD per share) \| $ / shares	$ 6.71	$ 5.67	$ 4.80

Stock-Based Compensation - Stock-based Compensation Expense (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax effect on stock-based compensation	$ (1,800,000)	$ (6,300,000)	$ 0
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	10,722,000	11,575,000	13,279,000
Tax effect on stock-based compensation	0	0	0
Total stock-based compensation, net of tax	10,722,000	11,575,000	13,279,000
Employee Stock \| Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	2,518,000	2,651,000	2,433,000
Employee Stock \| Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	3,329,000	3,490,000	3,529,000
Employee Stock \| Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation	$ 4,875,000	$ 5,434,000	$ 7,317,000

Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended									12 Months Ended
	Aug. 19, 2016	Jun. 24, 2016	May 02, 2016	May 28, 2015	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Mar. 29, 2014	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net					$ 12,697	$ 85	$ 6,910	$ 0	$ (3)	$ 59	$ 8	$ 503	$ 2,000	$ 7,288	$ 559	$ 2,668
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,700		$ 300	$ 1,500
Amortization period for stock-based compensation balance														2 years 2 months 11 days
Restricted Stock Units \| Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period														3 years
Restricted stock units granted (in shares)														2,296,210	1,540,250	1,900,000
Weighted average grant value (in USD per share)														$ 8.20	$ 8.64	$ 6.52
Total compensation cost not yet recognized, other than options					19,100									$ 19,100
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amortization period for stock-based compensation balance														2 years 6 days
Unamortized stock-based compensation balance					1,100									$ 1,100
Stock Options \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period														3 years
Stock option expiration date														5 years
Stock Options \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period														4 years
Stock option expiration date														10 years
Stock Options \| Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period														4 years
Options granted during the period (in shares)														152,276
Weighted average fair value (in USD per share)														$ 4.42
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense														$ 10,722	$ 11,575	$ 13,279
Total compensation cost not yet recognized, other than options					$ 200									$ 200
Amortization period for stock-based compensation balance														1 month
Issuance of common stock under the Employee Stock Purchase Plan (in shares)														557,281	565,493	586,386
Cascade Microtech \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 300
Options granted during the period (in shares)		152,276
Share-based Compensation Expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense														$ 300
Restructuring and impairment charges, net														964	$ 0	$ 0
Share-based Compensation Expense \| Cascade Microtech
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net							$ 700							700
Share-based Compensation Expense \| FormFactor
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net														$ 300	$ 500

Stock-Based Compensation - Valuation Assumptions (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%
Expected volatility	47.50%
Risk-free interest rate	1.60%
Expected term (in years)	5 years 6 months 6 days
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	45.43%	51.78%	41.71%
Risk-free interest rate	0.43%	0.12%	0.09%
Expected term (in years)	9 months 6 days	8 months	8 months

Income Taxes - Components of Loss Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
United States									$ (50,947)	$ (3,069)	$ (23,230)
Foreign									752	1,798	3,135
Loss before income taxes	$ (15,417)	$ (14,148)	$ (6,860)	$ (13,770)	$ (727)	$ (2,310)	$ 862	$ 904	$ (50,195)	$ (1,271)	$ (20,095)

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Current provision (benefit):
Federal									$ 0	$ (3)	$ (983)
State									120	72	(386)
Foreign									1,804	198	234
Total current provision (benefit)									1,924	267	(1,135)
Deferred provision (benefit):
Federal									(42,150)	0	0
State									(2,165)	0	0
Foreign									(1,247)	(15)	225
Total deferred provision (benefit)									(45,562)	(15)	225
Total provision (benefit) from income taxes	$ 26	$ 50	$ (43,744)	$ 30	$ (108)	$ 215	$ 24	$ 121	$ (43,638)	$ 252	$ (910)

Income Taxes - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Income Tax Disclosure [Abstract]
Federal statutory rate									35.00%	35.00%	35.00%
Income Tax Reconciliation
U.S. statutory federal tax rate									$ (17,568)	$ (445)	$ (7,033)
State taxes and credits, net of Federal benefit									(975)	17	(186)
Amortization of stock-based compensation									1,256	907	686
Research and development credits									(1,654)	(1,872)	(1,183)
Foreign taxes at rates different than the U.S.									504	(66)	(84)
Other permanent differences									2,048	238	(972)
Change in valuation allowance									(27,120)	1,457	7,886
Other									(129)	16	(24)
Total provision (benefit) from income taxes	$ 26	$ 50	$ (43,744)	$ 30	$ (108)	$ 215	$ 24	$ 121	$ (43,638)	$ 252	$ (910)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014	Dec. 28, 2013
Components of Deferred Tax Assets and Liabilities [Abstract]
Tax credits	$ 33,486	$ 30,968
Inventory reserve	13,863	14,010
Unrealized investment gains	0	20
Other reserves and accruals	10,593	5,953
Non-statutory stock options	6,206	4,936
Depreciation and amortization	7,719	13,440
Net operating loss carryforwards	118,482	119,327
Gross deferred tax assets	190,349	188,654
Valuation allowance	(150,581)	(176,196)	$ (187,759)	$ (180,913)
Total deferred tax assets	39,768	12,458
Acquired intangibles & fixed assets	(39,801)	(9,177)
Unrealized investment gains	(289)	0
Tax on undistributed earnings	(71)	0
Total deferred tax liabilities	(40,161)	(9,177)
Net deferred tax assets (liabilities)	$ (393)
Net deferred tax assets (liabilities)		$ 3,281

Income Taxes - Valuation Allowance Against Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Allowance against deferred tax assets
Allowance against deferred tax assets, Beginning balance	$ 176,196	$ 187,759	$ 180,913
Additions	0	0	6,846
Reduction	(25,615)	(11,563)	0
Allowance against deferred tax assets, Ending balance	150,581	$ 176,196	$ 187,759
California
Tax Credit Carryforward [Line Items]
State research credit carryforwards	29,900
Oregon
Tax Credit Carryforward [Line Items]
State research credit carryforwards	600
Singapore
Tax Credit Carryforward [Line Items]
Singapore net operating loss carryforwards	9,700
Federal
Tax Credit Carryforward [Line Items]
Federal research and development tax credit carryforwards	22,500
Net operating loss carryforwards	298,700
Federal foreign tax credit carryforwards	2,200
Alternative minimum tax credits	2,400
State
Tax Credit Carryforward [Line Items]
Net operating loss carryforwards	$ 271,700

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Income Tax Disclosure [Abstract]
Repatriation of earnings of foreign subsidiaries	$ 20,200,000
Additional U.S. income taxes	400,000
Tax effect on stock-based compensation	1,800,000	$ 6,300,000	$ 0
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit beginning balance	17,033,000	16,333,000	16,972,000
Additions based on tax positions related to the current year	614,000	667,000	498,000
Additions based on tax position from prior year	450,000	163,000	324,000
Reductions for tax positions of prior years	0	(18,000)	(1,109,000)
Reductions to unrecognized tax benefits due to lapse of the applicable statute of limitations	(119,000)	(112,000)	(352,000)
Unrecognized tax benefit ending balance	17,978,000	17,033,000	16,333,000
Tax-effected unrecognized tax benefits	1,300,000
Interest (benefit) charges and penalties	22,000	50,000	$ (100,000)
Accrued interest charges and penalties	$ 200,000	$ 200,000

Employee Benefit Plans (Details) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) $ in Millions	Dec. 31, 2016 USD ($) plan	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Compensation and Retirement Disclosure [Abstract]
Number of benefit plans \| plan	1,000
Cost recognized under defined contribution plans \| $	$ 0.5	$ 1.1	$ 1.0

Operating Segment and Geographic Information - Operating Results By Segment (Details) $ in Thousands			3 Months Ended								12 Months Ended
	Jun. 24, 2016 segment	Jun. 23, 2016 segment	Dec. 31, 2016 USD ($)	Sep. 24, 2016 USD ($)	Jun. 25, 2016 USD ($)	Mar. 26, 2016 USD ($)	Dec. 26, 2015 USD ($)	Sep. 26, 2015 USD ($)	Jun. 27, 2015 USD ($)	Mar. 28, 2015 USD ($)	Dec. 31, 2016 USD ($)	Dec. 26, 2015 USD ($)	Dec. 27, 2014 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	2	1
Number of operating segments \| segment	3	1
Segment Reporting Information [Line Items]
Revenues			$ 123,888	$ 123,299	$ 83,083	$ 53,611	$ 71,782	$ 65,862	$ 73,885	$ 70,829	$ 383,881	$ 282,358	$ 268,530
Gross profit			40,275	27,188	25,427	9,792	21,191	18,455	23,303	22,789	$ 102,682	$ 85,738	77,439
Gross margin											26.70%	30.40%
Operating income (loss)			$ (14,530)	$ (13,158)	$ (6,646)	$ (13,573)	$ (761)	$ (3,357)	$ 697	$ (682)	$ (47,907)	$ (4,103)	$ (20,558)
Operating Segments \| Probe Cards
Segment Reporting Information [Line Items]
Revenues											337,970	282,358
Gross profit											$ 121,407	$ 99,199
Gross margin											35.90%	35.10%
Operating income (loss)											$ 49,382	$ 39,964
Operating Segments \| Systems
Segment Reporting Information [Line Items]
Revenues											45,911	0
Gross profit											$ 23,925	$ 0
Gross margin											52.10%	0.00%
Operating income (loss)											$ 8,968	$ 0
Corporate and Other
Segment Reporting Information [Line Items]
Revenues											0	0
Gross profit											$ (42,650)	$ (13,461)
Gross margin											0.00%	0.00%
Operating income (loss)											$ (106,257)	$ (44,067)

Operating Segment and Geographic Information - Revenue by Country (Details) - Geographic Concentration Risk - Sales Revenue	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	100.00%	100.00%	100.00%
United States
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	33.30%	23.40%	28.10%
South Korea
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	17.10%	25.20%	19.60%
Taiwan
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	14.90%	21.90%	18.40%
Europe
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	12.90%	9.00%	11.40%
Asia-Pacific
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	11.40%	11.10%	12.90%
Japan
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	10.00%	9.40%	9.60%
Rest of the world
Product Information [Line Items]
Total revenues attributable to customers greater than 10%	0.40%	0.00%	0.00%

Operating Segment and Geographic Information - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Revenue from External Customers [Line Items]
Revenues	$ 123,888	$ 123,299	$ 83,083	$ 53,611	$ 71,782	$ 65,862	$ 73,885	$ 70,829	$ 383,881	$ 282,358	$ 268,530
Foundry & Logic
Revenue from External Customers [Line Items]
Revenues									237,591	145,839	142,360
DRAM
Revenue from External Customers [Line Items]
Revenues									86,910	125,512	110,800
Flash
Revenue from External Customers [Line Items]
Revenues									13,469	11,007	15,370
Systems
Revenue from External Customers [Line Items]
Revenues									$ 45,911	$ 0	$ 0

Operating Segment and Geographic Information - Major Customers With Revenues Greater Than 10% (Details) - Customer Concentration Risk - Sales Revenue	12 Months Ended
	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Revenue, Major Customer [Line Items]
Total revenues attributable to customers greater than 10%	30.10%	60.20%	51.60%
Intel
Revenue, Major Customer [Line Items]
Total revenues attributable to customers greater than 10%	30.10%	19.60%	19.70%
Samsung
Revenue, Major Customer [Line Items]
Total revenues attributable to customers greater than 10%		14.60%
SK hynix
Revenue, Major Customer [Line Items]
Total revenues attributable to customers greater than 10%		14.30%	16.90%
Micron
Revenue, Major Customer [Line Items]
Total revenues attributable to customers greater than 10%		11.70%	15.00%

Operating Segment and Geographic Information - Long-Lived Assets by Geographical Location (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 26, 2015
Long-Lived Assets [Line Items]
Long-lived assets	$ 357,281	$ 80,136
United States
Long-Lived Assets [Line Items]
Long-lived assets	323,369	77,257
Europe
Long-Lived Assets [Line Items]
Long-lived assets	30,903	655
Asia-Pacific
Long-Lived Assets [Line Items]
Long-lived assets	1,709	689
South Korea
Long-Lived Assets [Line Items]
Long-lived assets	733	1,128
Japan
Long-Lived Assets [Line Items]
Long-lived assets	510	295
Singapore
Long-Lived Assets [Line Items]
Long-lived assets	$ 57	$ 112

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2016	Sep. 24, 2016	Jun. 25, 2016	Mar. 26, 2016	Dec. 26, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Mar. 29, 2014	Dec. 27, 2014	Dec. 31, 2016	Dec. 26, 2015	Dec. 27, 2014
Quarterly Financial Data [Abstract]
Revenues	$ 123,888	$ 123,299	$ 83,083	$ 53,611	$ 71,782	$ 65,862	$ 73,885	$ 70,829			$ 383,881	$ 282,358	$ 268,530
Cost of revenues	83,613	96,111	57,656	43,819	50,591	47,407	50,582	48,040			281,199	196,620	191,091
Gross profit	40,275	27,188	25,427	9,792	21,191	18,455	23,303	22,789			102,682	85,738	77,439
Research and development	18,218	17,253	11,133	10,849	11,236	10,645	11,217	11,086			57,453	44,184	42,725
Selling, general and administrative	23,890	23,008	14,030	12,516	10,719	11,108	11,381	11,882			73,444	45,090	51,385
Restructuring and impairment charges, net	12,697	85	6,910	0	(3)	59	8	503	$ 2,000		7,288	559	2,668
Total operating expenses	54,805	40,346	32,073	23,365	21,952	21,812	22,606	23,471			150,589	89,841	97,997
Operating income (loss)	(14,530)	(13,158)	(6,646)	(13,573)	(761)	(3,357)	697	(682)			(47,907)	(4,103)	(20,558)
Interest income, net	59	52	88	117	70	65	65	85			327	285	302
Other income (expense), net	(946)	(1,042)	(302)	(314)	(36)	982	100	1,501			(2,615)	2,547	161
Loss before income taxes	(15,417)	(14,148)	(6,860)	(13,770)	(727)	(2,310)	862	904			(50,195)	(1,271)	(20,095)
Provision (benefit) from income taxes	26	50	(43,744)	30	(108)	215	24	121			(43,638)	252	(910)
Net loss	$ (15,443)	$ (14,198)	$ 36,884	$ (13,800)	$ (619)	$ (2,525)	$ 838	$ 783			$ (6,557)	$ (1,523)	$ (19,185)
Net loss per share: Basic (in USD per share)	$ (0.22)	$ (0.20)	$ 0.62	$ (0.24)	$ (0.01)	$ (0.04)	$ 0.01	$ 0.01
Net loss per share: Diluted (in USD per share)	$ (0.22)	$ (0.20)	$ 0.61	$ (0.24)	$ (0.01)	$ (0.04)	$ 0.01	$ 0.01
Weighted average number of shares used in per share calculations: Basic (in shares)	70,807	70,502	59,572	58,431	58,128	58,209	58,109	56,594			64,941	57,850	55,908
Weighted average number of shares used in per share calculations: Diluted (in shares)	70,807	70,502	59,988	58,431	58,128	58,209	59,094	58,838
Condensed Income Statements, Captions [Line Items]
Restructuring charges	$ 12,697	$ 85	$ 6,910	$ 0	$ (3)	$ 59	$ 8	$ 503	2,000		$ 7,288	$ 559	$ 2,668
Provision (benefit) from income taxes	26	$ 50	(43,744)	$ 30	$ (108)	215	$ 24	121			(43,638)	252	(910)
Impairment of long-lived assets											12,400	8	1,028
Other Nonoperating Income (Expense)
Condensed Income Statements, Captions [Line Items]
Proceeds from business interruption insurance recovery								$ 1,500				1,500
Other income (expense), net \| Settled Litigation \| MarTek
Condensed Income Statements, Captions [Line Items]
Gain related to legal settlement						$ 1,000
Employee Severance and Benefits
Quarterly Financial Data [Abstract]
Restructuring and impairment charges, net									1,400	$ 700	6,220	59	2,068
Condensed Income Statements, Captions [Line Items]
Restructuring charges									$ 1,400	$ 700	6,220	59	2,068
Share-based Compensation Expense
Quarterly Financial Data [Abstract]
Restructuring and impairment charges, net											964	0	0
Condensed Income Statements, Captions [Line Items]
Restructuring charges											964	$ 0	$ 0
Cascade Microtech
Quarterly Financial Data [Abstract]
Provision (benefit) from income taxes			(43,700)
Condensed Income Statements, Captions [Line Items]
Provision (benefit) from income taxes			(43,700)
Impairment of long-lived assets	$ 12,400
Cascade Microtech \| Employee Severance and Benefits
Quarterly Financial Data [Abstract]
Restructuring and impairment charges, net			5,400								5,400
Condensed Income Statements, Captions [Line Items]
Restructuring charges			5,400								5,400
Cascade Microtech \| Share-based Compensation Expense
Quarterly Financial Data [Abstract]
Restructuring and impairment charges, net			700								700
Condensed Income Statements, Captions [Line Items]
Restructuring charges			$ 700								$ 700

Business Interruption Insurance Claim Recovery (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 28, 2015	Dec. 26, 2015
Other Nonoperating Income (Expense)
Business Interruption Loss [Line Items]
Proceeds from business interruption insurance recovery	$ 1.5	$ 1.5