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Document and Entity Information Document - USD ($)	12 Months Ended
Document and Entity Information Document - USD ($)	Dec. 29, 2018	Feb. 20, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	FORMFACTOR INC.
Entity Central Index Key	0001039399
Current Fiscal Year End Date	--12-29
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 29, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding (in shares)		74,478,445
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 498,775,456
Entity Shell Company	false

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Current assets:
Cash and cash equivalents	$ 98,472	$ 91,184
Marketable securities	50,531	48,988
Accounts receivable, net	95,333	81,515
Inventories, net	77,706	67,848
Restricted cash	849	372
Refundable income taxes	1,260	2,242
Prepaid expenses and other current assets	13,669	13,705
Total current assets	337,820	305,854
Restricted cash	1,225	1,170
Property, plant and equipment, net	54,054	46,754
Goodwill	189,214	189,920
Intangibles, net	67,640	97,484
Deferred tax assets	77,301	3,133
Other assets	968	2,259
Total assets	728,222	646,574
Current liabilities:
Accounts payable	40,006	35,046
Accrued liabilities	27,731	33,694
Current portion of term loan, net of unamortized issuance cost of $160 and $307	29,840	18,443
Deferred revenue	4,941	4,978
Total current liabilities	102,518	92,161
Term loan, less current portion, net of unamortized issuance cost of $29 and $272	34,971	87,228
Deferred tax liabilities	2,355	3,379
Deferred rent and other liabilities	8,214	5,169
Total liabilities	148,058	187,937
Commitments and contingencies (Note 11)
Stockholders' equity:
10,000,000 shares authorized; no shares issued and outstanding	0	0
250,000,000 shares authorized; 74,139,712 and 72,532,176 shares issued and outstanding	74	73
Additional paid-in capital	862,897	843,116
Accumulated other comprehensive income	780	3,021
Accumulated deficit	(283,587)	(387,573)
Total stockholders' equity	580,164	458,637
Total liabilities and stockholders' equity	$ 728,222	$ 646,574

CONSOLIDATED BALANCE SHEETS (PARENTHETICAL) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Statement of Financial Position [Abstract]
Current unamortized debt issuance costs	$ 160	$ 307
Noncurrent unamortized debt issuance costs	$ 29	$ 272
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 outstanding (in shares)	74,139,712	72,532,176

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenues	$ 529,675	$ 548,441	$ 383,881
Cost of revenues	319,336	332,844	281,199
Gross profit	210,339	215,597	102,682
Operating expenses:
Research and development	74,976	73,807	57,453
Selling, general and administrative	99,094	94,679	73,444
Restructuring and impairment charges, net	160	810	19,692
Total operating expenses	174,230	169,296	150,589
Operating income (loss)	36,109	46,301	(47,907)
Interest income	1,356	548	327
Interest expense	(3,314)	(4,491)	(2,391)
Other expense, net	(224)	(152)	(224)
Income (loss) before income taxes	33,927	42,206	(50,195)
Provision (benefit) for income taxes	(70,109)	1,293	(43,638)
Net income (loss)	$ 104,036	$ 40,913	$ (6,557)
Net income (loss) per share:
Basic (in USD per share)	$ 1.42	$ 0.57	$ (0.10)
Diluted (in USD per share)	$ 1.38	$ 0.55	$ (0.10)
Weighted-average number of shares used in per share calculations:
Basic (in shares)	73,482	72,292	64,941
Diluted (in shares)	75,182	74,239	64,941

CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 104,036	$ 40,913	$ (6,557)
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(2,065)	6,764	(2,042)
Unrealized gains on the translation of deferred tax assets	163	0	0
Unrealized gains (losses) on available-for-sale marketable securities	(8)	(206)	29
Unrealized gains (losses) on derivative instruments	(331)	203	495
Other comprehensive income (loss), net of tax	(2,241)	6,761	(1,518)
Comprehensive income (loss)	$ 101,795	$ 47,674	$ (8,075)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances (in shares) at Dec. 26, 2015		58,088,969
Balances at Dec. 26, 2015	$ 294,681	$ 58	$ 718,904	$ (2,222)	$ (422,059)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)		232,190
Issuance of common stock pursuant to exercise of options for cash	2,003		2,003
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,579,218
Issuance of common stock pursuant to vesting of restricted stock units	2	$ 2
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		557,281
Issuance of common stock under the Employee Stock Purchase Plan	3,741	$ 1	3,740
Issuance of common stock pursuant to Cascade Microtech acquisition (in shares)		10,450,189
Issuance of common stock pursuant to Cascade Microtech acquisition	97,079	$ 10	97,069
Stock-based compensation	11,625		11,625
Other comprehensive income	(1,518)			(1,518)
Net income (loss)	(6,557)				(6,557)
Balances (in shares) at Dec. 31, 2016		70,907,847
Balances at Dec. 31, 2016	401,056	$ 71	833,341	(3,740)	(428,616)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)		1,473,389
Issuance of common stock pursuant to exercise of options for cash	13,837	$ 1	13,836
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,364,612
Issuance of common stock pursuant to vesting of restricted stock units	1	$ 1
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		655,961
Issuance of common stock under the Employee Stock Purchase Plan	5,695	$ 1	5,694
Issuance of common stock pursuant to Cascade Microtech acquisition	0
Common stock withheld from vesting of restricted stock units for tax (in shares)		(502,016)
Common stock withheld from vesting of restricted stock units for tax	(6,886)		(6,886)
Purchase and retirement of common stock (in shares)		(1,367,617)
Purchase and retirement of common stock	(18,970)	$ (1)	(18,969)
Stock-based compensation	16,230		16,230
ASU 2017-12 Adoption	0		(130)		130
Other comprehensive income	6,761			6,761
Net income (loss)	$ 40,913				40,913
Balances (in shares) at Dec. 30, 2017	72,532,176	72,532,176
Balances at Dec. 30, 2017	$ 458,637	$ 73	843,116	3,021	(387,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock pursuant to exercise of options for cash (in shares)		134,609
Issuance of common stock pursuant to exercise of options for cash	1,158		1,158
Issuance of common stock pursuant to vesting of restricted stock units (in shares)		1,287,107
Issuance of common stock pursuant to vesting of restricted stock units	1	$ 1
Issuance of common stock under the Employee Stock Purchase Plan (in shares)		610,297
Issuance of common stock under the Employee Stock Purchase Plan	6,662	$ 1	6,661
Issuance of common stock pursuant to Cascade Microtech acquisition	0
Common stock withheld from vesting of restricted stock units for tax (in shares)		(424,477)
Common stock withheld from vesting of restricted stock units for tax	(5,792)	$ (1)	(5,791)
Stock-based compensation	17,753		17,753
ASU 2017-12 Adoption	(50)				(50)
Other comprehensive income	(2,241)			(2,241)
Net income (loss)	$ 104,036				104,036
Balances (in shares) at Dec. 29, 2018	74,139,712
Balances at Dec. 29, 2018	$ 580,164	$ 74	$ 862,897	$ 780	$ (283,587)

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 104,036	$ 40,913	$ (6,557)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation	14,314	13,626	11,371
Amortization	29,373	30,940	35,427
Impairment of long-lived assets	0	0	12,400
Amortization (accretion) of discount on investments	(10)	38	(31)
Stock-based compensation expense	17,827	16,339	11,686
Amortization of debt issuance costs	390	619	307
Deferred income tax benefit	(74,908)	(590)	(45,022)
Provision (benefit) for doubtful accounts receivable	0	(99)	15
Provision for excess and obsolete inventories	10,479	9,259	6,631
Acquired inventory step-up amortization	0	569	10,022
Loss on disposal of long-lived assets	325	510	361
Non-cash restructuring	140	114	964
Foreign currency transaction losses (gains)	125	(1,717)	(77)
Gain on derivative instruments	0	(10)	(51)
Changes in assets and liabilities:
Accounts receivable	(13,830)	(10,651)	(6,847)
Inventories	(21,298)	(15,635)	(11,733)
Prepaid expenses and other current assets	262	870	(3,292)
Refundable income taxes	942	(413)	126
Other assets	707	61	(248)
Accounts payable	3,050	741	3,433
Accrued liabilities	(5,718)	810	786
Income taxes payable	(501)	62	(1,127)
Deferred rent and other liabilities	3,109	111	126
Deferred revenues	26	(30)	(283)
Net cash provided by operating activities	68,700	86,323	17,423
Cash flows from investing activities:
Acquisition of property, plant and equipment	(19,869)	(17,756)	(11,521)
Acquisition of Cascade Microtech, net of cash acquired	0	0	(228,031)
Proceeds from sale of subsidiary	94	68	47
Proceeds from sale of property and property, plant and equipment	23	0	53
Purchases of marketable securities	(30,566)	(50,733)	(10,587)
Proceeds from maturities of marketable securities	29,023	8,996	44,500
Net cash used in investing activities	(21,295)	(59,425)	(205,539)
Cash flows from financing activities:
Proceeds from issuances of common stock	7,712	19,510	5,745
Purchase and retirement of common stock	0	(18,970)	0
Tax withholdings related to net share settlements of equity awards	(5,791)	(6,885)	0
Proceeds from term loan	0	0	150,000
Payments on term loan	(41,250)	(33,125)	(10,625)
Payment of term loan issuance costs	0	0	(1,506)
Net cash provided by (used in) financing activities	(39,329)	(39,470)	143,614
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(256)	2,702	399
Net increase (decrease) in cash, cash equivalents and restricted cash	7,820	(9,870)	(44,103)
Cash, cash equivalents and restricted cash, beginning of year	92,726	102,596	146,699
Cash, cash equivalents and restricted cash, end of year	100,546	92,726	102,596
Non-cash investing and financing activities:
Fair value of stock issued in connection with the acquisition of Cascade Microtech	0	0	97,079
Fair value of stock options and restricted stock-based awards assumed in connection with the acquisition of Cascade Microtech	0	0	7,776
Fair value of vested stock options and restricted stock-based awards paid in cash in connection with the acquisition of Cascade Microtech	0	0	12,815
Change in accounts payable and accrued liabilities related to property, plant and equipment purchases	2,290	(33)	(732)
Supplemental disclosure of cash flow information:
Income taxes paid, net	4,576	3,172	2,567
Cash paid for interest	$ 3,113	$ 3,836	$ 2,110

Debt - Future Principle and Interest Payments $ in Thousands	Dec. 29, 2018 USD ($)
Debt Instrument [Line Items]
Principal, 2019	$ 30,000
Principal, 2020	35,000
Principal, total	65,000
Interest, 2019	2,190
Interest, 2020	556
Interest, total	$ 2,746
Stated rate	4.35%

Formation and Business of the Company	12 Months Ended
Formation and Business of the Company	Dec. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Formation and Business of the Company	Formation and Nature of Business FormFactor, Inc. was incorporated in Delaware on April 15, 1993 and is headquartered in Livermore, California. We are a leading provider of electrical test and measurement technologies. We provide a broad range of high-performance probe cards, analytical probes, probe stations and thermal sub-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 from research, to development through production. Customers use our products and services to lower production costs, improve yields, and enable development of complex next generation products. 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 29, 2018, December 30, 2017 and December 31, 2016 consisted of 52 weeks, 52 weeks and 53 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. 29, 2018

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.

On June 24, 2016, we completed the acquisition of Cascade Microtech and, accordingly, our Consolidated Statements of Operations include the results of operations of Cascade Microtech since that date. See Note 4.

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 on our Consolidated Balance Sheets under Accumulated other comprehensive income.

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 a component of Other income (expense), net 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, which 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. 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 classify our marketable securities as available-for-sale and, accordingly, report them at fair value with the related unrealized gains and losses included in Accumulated other comprehensive income in our Consolidated Balance Sheets. Any unrealized losses which are considered to be other-than-temporary are recorded in Other income (expense), net, in the Consolidated Statements of Operations. Realized gains and 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 difference between the investment's amortized cost basis and its fair value. We did not record any other-than-temporary impairments during fiscal 2018, 2017 or 2016.

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 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 Sheets. We do not use derivative financial instruments for trading or speculative purposes.

Accounts Receivable and Allowance for Doubtful Accounts

The majority of our accounts receivable are derived from sales to large multinational semiconductor manufacturers throughout the world, are recorded at their invoiced amount and do not bear interest.

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.

Activity related to our allowance for doubtful accounts receivable was as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Balance at beginning of year	$	200		$	299		$	284
Charges (reversals) to costs and expenses	(15		)	(99		)	51
Write-offs	—			—			(36		)
Balance at end of year	$	185		$	200		$	299

Inventories

Inventories are stated at the lower of cost (principally standard cost which approximates actual cost on a first-in, first-out basis) or net realizable value.

The provision for potentially excess and obsolete inventory is made based on management's analysis of current inventory levels, and consideration primarily of past consumption, recent purchases and backlog. On a quarterly basis, we review inventory quantities on hand and on order under non-cancelable purchase commitments in comparison to our past consumption, recent purchases, backlog and other factors 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. 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 custom product into a market that has been subject to cyclicality and significant demand fluctuations. Many of 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 charges to Cost of revenues.

Inventory write downs totaled $10.5 million, $9.3 million and $6.6 million for fiscal 2018, 2017 and 2016, respectively.

Restricted Cash

Restricted cash is comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases, customer deposits, and temporary customs import permits.

Property, Plant, and Equipment

Property, plant 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. Machinery and equipment, computer equipment and software, and furniture and fixtures are depreciated over 1 to 5 years.

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 Consolidated Balance Sheets and the resulting gain or loss is reflected in Operating income (loss) in our Consolidated Statements of Operations.

Goodwill

Goodwill represents the excess of the purchase price over the fair value of identifiable assets acquired and liabilities assumed. Goodwill is not amortized, rather assessed, at least annually, for impairment at a reporting unit level. Impairment of goodwill exists when the carrying amount of a reporting unit exceeds its fair value. A goodwill impairment loss is recognized for the amount that the carrying amount of the reporting unit, including goodwill, exceeds its fair value, limited to the total amount of goodwill allocated to that reporting unit. If the fair value of a reporting unit exceeds the carrying amount, goodwill of the reporting unit is not considered impaired.

We evaluate impairment by first assessing qualitative factors to determine whether it is necessary to perform a quantitative impairment test. If we determine, 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.

We perform our annual goodwill impairment test in the fourth quarter of each year by assessing qualitative factors, including, but not limited to an assessment of our market capitalization, which was significantly higher than our book value. Based on these tests, we determined that the quantitative impairment test was not required and no impairment charges were recorded in fiscal 2018, 2017 or 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 analysis. If the results of these analysis are lower than current estimates, a material impairment charge may result at that time.

See Note 10 for additional information.

Intangible Assets

Intangible assets consist of acquisition related intangible assets and intellectual property. The intangible assets are being amortized over periods of 1 to 10 years, which reflect the pattern in which economic benefits of the assets are expected to be realized. 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.

See Note 10 for additional information.

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.

See Note 7 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 accounts receivable. 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 relatively narrow base of customers and generally do not require collateral.

The following customer represented 10% or more of our revenues:



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Intel Corporation	19.0	%	25.9	%	30.1	%

At December 29, 2018, two customers accounted for 27.8% and 13.0% of gross accounts receivable, respectively. At December 30, 2017, one customer accounted for 24.1% of gross accounts receivable. No other customers accounted for 10% or more of gross accounts receivable for these fiscal period ends. We operate in the competitive semiconductor industry, including the Dynamic Random Access Memory, or DRAM, Flash memory, and Foundry & Logic and probe stations 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

Revenue is recognized upon transferring control of products and services, and the amounts recognized reflect the consideration we expect to be entitled to receive in exchange for these products and services. Revenue is recognized net of any taxes collected from customers, which are subsequently remitted to governmental authorities. An arrangement may include some or all of the following products and services: probe cards, systems, accessories, installation services, service contracts and extended warranty contracts. We sell our products and services direct to customers and to partners in two distribution channels: global direct sales force and through a combination of manufacturers’ representatives and distributors.

A performance obligation is a promise in a contract to transfer a distinct good or service to the customer. In contracts with multiple performance obligations, we identify each performance obligation and evaluate whether the performance obligation is distinct within the context of the contract at contract inception. Performance obligations that are not distinct at contract inception are combined and accounted for as one unit of account. Generally, the performance obligations in a contract are considered distinct within the context of the contract and are accounted for as separate units of account.

Our products may be customized to our customers’ specifications, however, control of our product is typically transferred to the customer at the point in time the product is either shipped or delivered, depending on the terms of the arrangement, as the criteria for overtime recognition is not met. In limited circumstances, substantive acceptance by the customer exists which results in the deferral of revenue until acceptance is formally received from the customer. Judgment may be required in determining if the acceptance clause is substantive.

Installation services are routinely provided to customers purchasing our systems. Installation services are a distinct performance obligation apart from the systems and recognized in the period they are performed. Service contracts, which include repair and maintenance service contracts, and extended warranty contracts are also distinct performance obligations and recognized over the contractual service period, which ranges from one to three years. For these service contracts recognized over time, we use an input measure, days elapsed, to measure progress.

A contract’s transaction price is allocated to each distinct performance obligation and recognized as revenue when, or as, the performance obligation is satisfied. In determining the transaction price, we evaluate whether the price is subject to refund or adjustment to determine the net consideration to which we expect to be entitled. We generally do not grant return privileges, except for defective products during the warranty period. Sales incentives and other programs that we may make available to these customers are considered to be a form of variable consideration, which is estimated in determining the contract’s transaction price to be allocated to the performance obligations. We have elected the practical expedient under Accounting Standards Codification (“ASC”) 606-10-32-18 to not assess whether a contract has a significant financing component as our standard payment terms are less than one year.

For contracts with multiple performance obligations, we allocate the contract’s transaction price to each performance obligation based on its relative stand-alone selling price. The stand-alone selling prices are determined based on observable prices, which are the prices at which we separately sell these products. For items which do not have observable prices, we use our best estimate of the stand-alone selling prices.

Transaction price allocated to the remaining performance obligations: On December 29, 2018, we had $3.4 million of remaining performance obligations, which were comprised of deferred service contracts and extended warranty contracts not yet delivered. We expect to recognize approximately 77.7% of our remaining performance obligations as revenue in fiscal 2019, and approximately 22.3% in fiscal 2020 and thereafter. The foregoing excludes the value of remaining performance obligations that have original durations of one year or less, and also excludes information about variable consideration allocated entirely to a wholly unsatisfied performance obligation.

Contract balances: The timing of revenue recognition may differ from the timing of invoicing to customers. Accounts receivable is recorded at the invoiced amount, net of an allowance for doubtful accounts. A receivable is recognized in the period we deliver goods or provide services or when our right to consideration is unconditional. A contract asset is recorded when we have performed under the contract but our right to consideration is conditional on something other than the passage of time. Contract assets as of December 29, 2018 and December 30, 2017 were $0.3 million and $1.6 million, respectively, and are reported on the Consolidated Balance Sheets as a component of Prepaid expenses and other current assets.

Contract liabilities include payments received in advance of performance under a contract and are satisfied as the associated revenue is recognized. Contract liabilities are reported on the Consolidated Balance Sheets on a contract-by-contract basis at the end of each reporting period as a component of Deferred revenue and Deferred rent and other liabilities. Contract liabilities totaled $5.7 million at both December 29, 2018 and December 30, 2017. During fiscal 2018, we recognized $4.8 million of revenue that was included in contract liabilities as of December 30, 2017.

Costs to obtain a contract: We generally expense sales commissions when incurred as a component of Selling, general and administrative expense as the amortization period is typically less than one year.

Revenue by Category: Refer to Note 16 of Notes to Consolidated Financial Statements for further details.

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 Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Balance at beginning of year	$	3,662		$	2,972		$	1,116
Warranty reserve from acquisition-Cascade Microtech	—			—			795
Accruals	3,181			8,115			5,254
Settlements	(4,741		)	(7,425		)	(4,193		)
Balance at end of year	$	2,102		$	3,662		$	2,972

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.

Restructuring Charges

Restructuring charges are comprised of costs related to employee termination benefits, long-lived assets and inventory 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.

We recorded restructuring charges of $0.2 million, $0.8 million and $7.3 million for fiscal years 2018, 2017 and 2016, respectively.

See Note 6 for additional information.

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. In evaluating the ability to recover deferred tax assets, we consider all available positive and negative evidence giving greater weight to our recent cumulative income, our historical ability to utlize net operating losses in recent years and our 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 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 in the Consolidated Balance Sheets.

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 related liability reflects the most likely outcome. We adjust the liability, as well as the related interest, in light of changing facts and circumstances. Settlement of any particular position could require the use of cash.

See Note 14 for additional information, including the Tax Cuts and Jobs Act enacted in December 2017.

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 Statements of Operations. The fair value of stock options is measured using the Black-Scholes option pricing model, while the fair value for restricted stock units ("RSUs") is measured based on the closing market price of our common stock on the date of grant. The fair value of Performance RSUs ("PRSU") is based on certain market performance criteria is measured using the Monte Carlo simulation pricing model.

See Notes 12 and 13 for additional information.

Net Income (Loss) Per Share

Basic net income (loss) per share is computed by dividing net income (loss) by the weighted-average number of common shares outstanding for the period. Diluted net income (loss) per share is computed giving effect to all potentially dilutive common stock and common stock equivalents, including stock options, RSUs and common stock subject to repurchase.

The following table reconciles the shares used in calculating basic net income (loss) per share and diluted net income (loss) per share (in thousands):



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Weighted-average shares used in computing basic net income (loss) per share	73,482	72,292	64,941
Add potentially dilutive securities	1,700	1,947	—
Weighted-average shares used in computing basic and diluted net income (loss) per share	75,182	74,239	64,941

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



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Options to purchase common stock	—	—	2,198
Restricted stock units	—	1	3,113
Employee stock purchase plan	—	—	10
Total potentially dilutive securities	—	1	5,321

Accumulated Other Comprehensive Income

Accumulated other comprehensive income ("OCI") includes the following items, the impact of which has been excluded from earnings and reflected as components of stockholders' equity as shown below (in thousands):



	December 29, 2018			December 30, 2017
Unrealized losses on marketable securities	$	(668	)	$	(660	)
Cumulative translation adjustments	918			2,983
Unrealized gains on derivative instruments	367			698
Unrealized gains on the translation of deferred tax assets	163			—
Accumulated other comprehensive income	$	780		$	3,021

Balance Sheet Components

12 Months Ended

Dec. 29, 2018

Balance Sheet Components [Abstract]

Balance Sheet Components

Marketable Securities

Marketable securities consisted of the following (in thousands):



December 29, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	7,997	$	1	$	(1	)	$	7,997
Commercial paper	2,296		—		(1		)	2,295
Corporate bond	30,833		1		(160		)	30,674
Certificate of deposit	960		—		(3		)	957
Agency securities	8,667		—		(59		)	8,608
	$	50,753	$	2	$	(224	)	$	50,531



December 30, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	3,968	$	—	$	(5	)	$	3,963
Commercial paper	3,000		—		—			3,000
Corporate bond	30,785		1		(150		)	30,636
Certificate of deposit	960		—		(3		)	957
Agency securities	10,489		—		(57		)	10,432
	$	49,202	$	1	$	(215	)	$	48,988

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 (loss) 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 gains and losses in fiscal 2018 and 2017 were caused primarily by changes in interest rates.

The longer the duration of marketable 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, current market liquidity, interest rate risk, the financial condition of the issuer, and credit rating downgrades. As of December 29, 2018 and December 30, 2017, $0.1 million and none, respectively, of our investments had been in a continuous loss position for 12 months or more.

The contractual maturities of marketable securities were as follows (in thousands):



	December 29, 2018				December 30, 2017
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	35,269	$	35,172	$	23,009	$	22,966
Due after one year to five years	15,484		15,359		26,193		26,022
	$	50,753	$	50,531	$	49,202	$	48,988

See also Note 9.

Fair Value

12 Months Ended

Dec. 29, 2018

Fair Value Disclosures [Abstract]

Fair Value

Whenever possible, the fair values of our financial assets and liabilities are determined using quoted market prices of identical securities or quoted market prices of similar securities 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 securities;


•	Level 2 valuations utilize significant observable inputs, 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 utilize 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.

We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during fiscal 2018, 2017 or 2016.

The carrying values of Cash, Accounts receivable, net, Restricted cash, Prepaid expenses and other current assets, Accounts payable and Accrued liabilities approximate fair value due to their short maturities.

No changes were made to our valuation techniques during fiscal 2018.

Cash Equivalents

The fair value of our cash equivalents is determined based on quoted market prices for similar or identical securities.

Marketable Securities

We classify our marketable securities as available-for-sale and value them utilizing a market approach. Our investments are priced by pricing vendors who provide 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 value. Our broker-priced investments are categorized as Level 2 investments because fair value is 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 value is appropriate.

Assets Measured at Fair Value on a Recurring Basis

Assets measured at fair value on a recurring basis were as follows (in thousands):



December 29, 2018	Level 1		Level 2		Total
Assets:
Cash equivalents:
Money market funds	$	1,184	$	—	$	1,184
Marketable securities:
U.S. Treasuries	7,997		—		7,997
Certificates of deposit	—		957		957
Agency securities	—		8,608		8,608
Corporate bonds	—		30,674		30,674
Commercial paper	—		2,295		2,295
	7,997		42,534		50,531
Interest rate swap derivative contracts	—		871		871
Total assets	$	9,181	$	43,405	$	52,586



December 30, 2017	Level 1		Level 2		Total
Assets:
Cash equivalents:
Money market funds	$	1,064	$	—	$	1,064
Corporate bonds	—		774		774
	1,064		774		1,838
Marketable securities:
U.S. Treasuries	3,963		—		3,963
Certificates of deposit	—		957		957
Agency securities	—		10,432		10,432
Corporate bonds	—		30,636		30,636
Commercial paper	—		3,000		3,000
	3,963		45,025		48,988
Foreign exchange derivative contract	—		31		31
Interest rate swap derivative contracts	—		1,043		1,043
Total assets	$	5,027	$	46,873	$	51,900

We did not have any liabilities measured at fair value on a recurring basis at December 29, 2018 or December 30, 2017.

Assets and Liabilities 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. Other than as discussed in Note 4 and Note 7, there were no assets or liabilities measured at fair value on a nonrecurring basis during fiscal 2018, 2017 or 2016.

- 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. 29, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Goodwill and Intangible Assets

Goodwill

Goodwill by reportable segment was as follows (in thousands):



	Probe Cards		Systems			Total
Goodwill, gross, as of December 26, 2015	$	30,731	$	—		$	30,731
Additions - Cascade Microtech acquisition	141,751		16,390			158,141
Foreign currency translation	—		(862		)	(862		)
Goodwill, gross, as of December 31, 2016	172,482		15,528			188,010
Foreign currency translation	—		1,910			1,910
Goodwill, gross, as of December 30, 2017	172,482		17,438			189,920
Foreign currency translation	—		(706		)	(706		)
Goodwill, gross, as of December 29, 2018	$	172,482	$	16,732		$	189,214

We have not recorded any goodwill impairments as of December 29, 2018.

Intangible Assets

Intangible assets were as follows (in thousands):



	December 29, 2018						December 30, 2017
Other Intangible Assets	Gross		Accumulated Amortization		Net		Gross		Accumulated Amortization		Net
Existing developed technologies	$	143,408	$	97,111	$	46,297	$	143,966	$	76,826	$	67,140
Trade name	12,023		9,173		2,850		12,086		5,735		6,351
Customer relationships	40,146		21,653		18,493		40,313		16,320		23,993
Backlog	—		—		—		15,811		15,811		—
	$	195,577	$	127,937	$	67,640	$	212,176	$	114,692	$	97,484

Amortization expense was included in our Consolidated Statements of Operations as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Cost of revenues	$	20,530	$	22,800	$	30,039
Selling, general and administrative	8,843		8,140		5,388
	$	29,373	$	30,940	$	35,427

The estimated future amortization of intangible assets is as follows (in thousands):



Fiscal Year	Amount
2019	$	26,387
2020	23,377
2021	12,628
2022	3,206
2023	2,042
Total	$	67,640

We did not record any impairment of intangible assets in fiscal 2018 or 2017. 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. See Note 7 for additional information.

Commitments and Contingencies

12 Months Ended

Dec. 29, 2018

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 fiscal 2018, 2017 and 2016 was $8.4 million, $7.9 million and $6.5 million, respectively.

Future minimum payments under our non-cancelable operating leases were as follows as of December 29, 2018 (in thousands):



Fiscal year:	Amount
2019	$	6,256
2020	6,522
2021	5,742
2022	4,786
2023	4,355
Thereafter	20,382
Total	$	48,043

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 2018, 2017 or 2016. 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 Consolidated Balance Sheets as of December 29, 2018 or December 30, 2017.

Legal Matters

From time to time, we may be subject to legal proceedings and claims in the ordinary course of business. As of December 29, 2018, and as of the filing of these financial statements, we were not involved in any material legal proceedings. In the future, we may become a party to additional legal proceedings that may require us to spend significant resources. Litigation can be expensive and disruptive to normal business operations. The results of legal proceedings are difficult to predict, and the costs incurred in litigation can be substantial, regardless of outcome.

In August 2013, a former employee filed a class action lawsuit against us in the Superior Court of California for the County of Alameda alleging violations of California’s wage and hour laws and other claims on behalf of himself and all similarly situated current and former employees at our Livermore facilities. On August 25, 2017, the court granted final approval of the parties’ agreement to settle the lawsuit. The settlement provided for payment by us of $1.5 million, which was accrued as of December 31, 2016 and paid during the third quarter of fiscal 2017.

Stockholders' Equity

12 Months Ended

Dec. 29, 2018

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, if any, of all classes of stock outstanding having priority rights as to dividends. No dividends have been declared or paid as of December 29, 2018.

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 2015, we repurchased and retired 1,013,162 shares of common stock for approximately $8.2 million. During fiscal 2016, we did not repurchase any shares under this program.

In February 2017, our Board of Directors authorized a program to repurchase up to $25 million of outstanding common stock to offset potential dilution from issuances of common stock under our stock-based incentive plans. The share repurchase program will expire on February 1, 2020. During fiscal 2018, we did not repurchase any shares. During fiscal 2017, we repurchased 1,367,617 shares of common stock for $19.0 million and, as of December 29, 2018, $6.0 million remained available for future repurchases.

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, as amended (the "2012 Plan") which was approved by our stockholders. As amended, the 2012 Plan has authorized for issuance a total of 17.9 million shares, 4.9 million of which were available for grant as of December 29, 2018.

RSUs granted under the 2012 Plan generally vest over three years in annual tranches, though we have granted, and will continue to grant, such awards that vest over a shorter term for employee retention purposes.

The 2012 Plan provides that incentive stock options may be granted to our employees and 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 our common stock on the date of grant. All restricted stock units and options granted under the 2012 Plan generally vest over three years and expire after seven years, unless otherwise determined by the Compensation Committee of the Board of Directors.

Stock Options

Stock option activity was as follows:



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 30, 2017	659,334		$	8.12
Options exercised	(134,609	)	8.60
Outstanding at December 29, 2018	524,725		$	8.00	3.1	$	3,155,659
Vested and expected to vest at December 29, 2018	524,725		$	8.00	3.1	$	3,155,659
Exercisable at December 29, 2018	401,105		$	7.94	3.0	$	2,435,515

Restricted Stock Units

RSUs are converted into shares of our common stock upon vesting on a one-for-one basis. The vesting of RSUs is subject to the employee's continuing service. RSU activity was as follows:



	Number of Shares		Weighted Average Grant Date Fair Value
Restricted stock units at December 30, 2017	3,148,061		$	11.22
Granted	1,551,770		13.79
Vested	(1,287,107	)	10.43
Canceled	(310,498	)	11.66
Restricted stock units at December 29, 2018	3,102,226		12.79

Performance Restricted Stock Units

The Performance RSUs ("PRSU") granted in fiscal 2018, 2017 and 2016 listed below vest based on us achieving certain market performance criteria. The performance criteria are based on a metric called Total Shareholder Return ("TSR") for the performance period of two or three years, relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies) as of a specific date.

PRSU activity was as follows:



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Grant Date	August 16, 2018	July 20, 2017	August 19, 2016
Performance period	July 1, 2018 - June 30, 2021	July 1, 2017 - June 30, 2020	April 1, 2016 - March 31, 2019
Number of shares	318,100	333,333	195,000
TSR as-of date	August 16, 2018	July 1, 2017	April 1, 2016
Stock-based compensation	$4.7 million	$4.1 million	$2.0 million

Employee Stock Purchase Plan

Our 2012 Employee Stock Purchase Plan (the "ESPP"), as amended, allows for the issuance of a total of 7,000,000 shares. The offering periods under the ESPP 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 2018, employees purchased 610,297 shares under this program at a weighted average exercise price of $12.84 per share, which represented a weighted average discount of $2.82 per share from the fair value of the stock purchased. As of December 29, 2018, 3,201,493 shares remained available for issuance.

Stock-Based Compensation

12 Months Ended

Dec. 29, 2018

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

Stock-Based Compensation

Stock-Based Compensation Expense

Certain information regarding our stock-based compensation was as follows (in thousands, except per share amounts):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Weighted average grant date per share fair value of stock options granted	$	—	$	—	$	2.00
Weighted average grant date per share fair value of RSUs granted	13.79		13.20		8.20
Total intrinsic value of stock options exercised	631		5,946		558
Fair value of RSUs vested	17,541		18,339		12,441

Stock-based compensation expense was included in the Consolidated Statement of Operations as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Stock-based compensation expense included in:
Cost of revenues	$	3,525	$	3,539	$	2,518
Research and development	5,398		5,341		3,329
Selling, general and administrative	8,904		7,350		4,875
Restructuring and impairment charges, net	—		109		964
Total stock-based compensation	$	17,827	$	16,339	$	11,686

Unrecognized Stock-Based Compensation Expense

Unrecognized stock-based compensation expense at December 29, 2018 consisted of the following (in thousands):

Valuation Assumptions

The following assumptions were used in estimating the fair value of options awarded and Employee Stock Purchase Plan:



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
2012 Equity Incentive Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	—	%	—	%	43.76	%
Risk-free interest rate	—	%	—	%	1.57	%
Expected life (in years)	0		0		5.5

Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	44.85%-48.94%		46.20%-46.33%		43.76%-46.48%
Risk-free interest rate	0.83%-2.22%		0.65%-1.15%		0.40%-0.47%
Expected life (in years)	0.5-1.0		0.5-1.0		0.5-1.0

Income Taxes

12 Months Ended

Dec. 29, 2018

Income Tax Disclosure [Abstract]

Income Taxes

Components of Income (Loss) Before Income Taxes

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



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
United States	$	20,877	$	31,492	$	(50,947	)
Foreign	13,050		10,714		752
	$	33,927	$	42,206	$	(50,195	)

Provision for Income Taxes

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



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Current provision (benefit):
Federal	$	79		$	(2,130	)	$	—
State	388			17			120
Foreign	4,687			4,069			1,804
	5,154			1,956			1,924
Deferred provision (benefit):
Federal	(72,295		)	66			(42,150		)
State	(2,056		)	—			(2,165		)
Foreign	(912		)	(729		)	(1,247		)
	(75,263		)	(663		)	(45,562		)
Total provision (benefit) for income taxes	$	(70,109	)	$	1,293		$	(43,638	)

Tax Rate Reconciliation

The following is a reconciliation of the difference between income taxes computed by applying the federal statutory rate of 21% for fiscal 2018 and for our deferred tax provision in fiscal 2017 and 35% for the current tax provision in fiscal 2017 and for the entire tax provision (benefit) in fiscal 2016 (in thousands):



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
U.S. statutory federal tax rate	$	7,125		$	14,772		$	(17,568	)
State taxes, net of federal benefit	778			951			(975		)
Stock-based compensation	(453		)	(1,428		)	1,256
Research and development credits	(3,213		)	(1,979		)	(1,654		)
Foreign taxes at rates different than the U.S.	1,287			(271		)	504
Other permanent differences	152			160			2,048
Global intangible low-taxed income	1,828			—			—
Mandatory deemed repatriation	—			1,655			—
Change in valuation allowance	(75,803		)	(12,207		)	(27,120		)
Other	(1,810		)	(360		)	(129		)
Total	$	(70,109	)	$	1,293		$	(43,638	)

Deferred Tax Assets and Liabilities

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 basis using enacted tax rates in effect for the year in which the differences are expected to be reversed.

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



	As of
	December 29, 2018			December 30, 2017
Tax credits	$	39,586		$	35,484
Inventory reserve	10,850			10,763
Other reserves and accruals	5,398			5,667
Non-statutory stock options	2,722			2,642
Depreciation and amortization	1,979			3,677
Net operating loss carryforwards	61,275			70,457
Gross deferred tax assets	121,810			128,690
Valuation allowance	(34,037		)	(109,840		)
Total deferred tax assets	87,773			18,850
Acquired intangibles and fixed assets	(12,667		)	(18,921		)
Unrealized investment gains	(107		)	(109		)
Tax on undistributed earnings	(53		)	(66		)
Total deferred tax liabilities	(12,827		)	(19,096		)
Net deferred tax assets (liabilities)	$	74,946		$	(246	)

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. From the fourth quarter of fiscal year 2009 to the third quarter of fiscal year 2018, we maintained a 100% valuation allowance against most of our U.S. deferred tax assets because there was insufficient positive evidence to overcome the existing negative evidence such that it was not more likely than not that the U.S. deferred tax assets were realizable. While we reported U.S. pre-tax income in fiscal year 2015 and 2017, because we reported U.S. pre-tax losses during the previous seven fiscal years, we continued to maintain the 100% valuation allowance through the third quarter of fiscal year 2018.

As of December 29, 2018, we had reported positive operating performance in the U.S. for two consecutive fiscal years and had also reported a cumulative three-year U.S. pre-tax profit. In addition, during the fourth quarter of fiscal year 2018, we completed our financial plan for fiscal year 2019 and expect continued positive operating performance in the U.S. We also considered forecasts of future taxable income and evaluated the utilization of net operating losses and tax credit carryforwards prior to their expiration. After considering these factors, we determined that the positive evidence overcame any negative evidence and concluded that it was more likely than not that the U.S. deferred tax assets were realizable. As a result, we released the valuation allowance against a significant portion of the U.S. federal deferred tax assets and a portion of the U.S. state deferred tax assets during the fourth quarter of fiscal year 2018.

The valuation allowance decreased by $75.8 million in fiscal year 2018, primarily due to the release of the valuation allowance on U.S. deferred tax assets. As of December 29, 2018, we maintained a valuation allowance of $34.0 million, primarily related to California deferred tax assets and foreign tax credit carryovers, due to uncertainty about the future realization of these assets.

In accordance with rates specified in The Tax Cuts and Jobs Act (“the Tax Act”), we revalued our net deferred tax asset at 21% in the fourth quarter of fiscal 2017, which resulted in a reduction in the value of our net deferred tax asset of $31.3 million, which was offset by a corresponding decrease in the valuation allowance and did not impact our Statements of Operations in fiscal 2017.

Tax Credits and Carryforwards

Tax credits and carryforwards available to us at December 29, 2018 consisted of the following (in thousands):



	Amount		Latest Expiration Date
Federal research and development tax credit	$	33,837	2021-2038
Federal net operating loss carryforwards	201,484		2030-2035
Foreign tax credit carryforwards	1,325		2019-2028
Alternative minimum tax credits	391		Indefinite
California research credits	32,964		Indefinite
Oregon research credits	281		2019-2022
State net operating loss carryforwards	250,873		2024-2036
Singapore net operating loss carryforwards	8,949		Indefinite

Undistributed Earnings

As of December 29, 2018, unremitted earnings of foreign subsidiaries was estimated at $18.4 million and were subject to U.S. federal income tax due to the Tax Act one-time transition tax on the deemed repatriation of undistributed foreign earnings and profits. The enactment of the Tax Act also resulted in a reassessment of the permanent reinvestment of undistributed foreign earnings. We intend to permanently invest $12.0 million of undistributed earnings indefinitely outside of the U.S. To the extent we repatriate the remaining $6.4 million of undistributed foreign earnings to the U.S., we established a deferred tax liability of $53 thousand for foreign withholding taxes. Our estimates are provisional and subject to further analysis.

Unrecognized Tax Benefits

We recognize the benefits of tax return positions if we determine that the positions are “more-likely-than-not” to be sustained by the taxing authority. Interest and penalties accrued on unrecognized tax benefits are recorded as tax expense in the period incurred.

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



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Unrecognized tax benefit, beginning balance	$	18,296		$	17,978		$	17,033
Additions based on tax positions related to the current year	1,677			694			614
Additions based on tax positions from prior years	5,332			—			450
Reductions for tax positions of prior years	(7		)	—			—
Reductions due to lapse of the applicable statute of limitations	(74		)	(376		)	(119		)
Unrecognized tax benefit, ending balance	$	25,224		$	18,296		$	17,978

Interest and penalties recognized as a component of Provision (benefit) for income taxes	$	71		$	67		$	22
Interest and penalties accrued at period end	230			218			209

Of the unrecognized tax benefits at December 29, 2018, $12.3 million would impact the effective tax rate if recognized.

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 29, 2018, 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 file income tax returns in the U.S. federal jurisdiction, various states and non U.S. jurisdictions. Our significant income tax jurisdictions are the U.S. (federal), California, Oregon, Germany and Japan. As a result of our net operating loss carryforwards, the statute of limitations is open for audit for tax years 2007 and forward for U.S. federal purposes, 2008 and forward for California purposes and 2015 and forward for Oregon purposes. For Germany, the statute of limitations is open for audit for tax years 2014 and forward. For Japan, the statute of limitations is open for audit for tax years 2013 and forward.

Tax Cuts and Jobs Act of 2017

The Tax Act was enacted in December 2017. The Tax Act significantly changes U.S. tax law effective January 1, 2018 by, among other things, lowering U.S. corporate income tax rates from 35% to 21%, repealing corporate alternative minimum tax, implementing a territorial tax system and imposing a one-time transition tax on deemed repatriated earnings of foreign subsidiaries.

The Tax Act provided for the repeal of corporate alternative minimum tax and made AMT tax credits fully refundable in future years. As a result, we reassessed the realizability of our deferred tax assets and released the valuation allowance against $0.8 million of AMT tax credits at December 30, 2017.

Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to reverse. As a result of the reduction in the U.S. corporate income tax rate, we revalued our ending U.S. deferred tax assets at December 30, 2017, offset by a corresponding change in the U.S. valuation allowance with no material impact to the fiscal 2017 tax provision.

The Tax Act provided for a one-time transition tax on the deemed repatriation of post-1986 undistributed foreign subsidiary earnings and profits (“E&P”). The estimated tax effects of the provisional income inclusion of $15.7 million for the deemed repatriation transition tax was fully offset by the benefit of current and carryforward foreign tax credits previously subjected to a full valuation allowance. We paid no U.S. federal cash taxes on the deemed repatriation. The deemed repatriation of undistributed foreign earnings also resulted in a reassessment of the permanent reinvestment of undistributed foreign earnings and profits and we established a deferred tax liability of $66 thousand for withholding taxes associated with those earnings which were not permanently reinvested as of December 30, 2017.

The SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Act and allows the registrant to record provisional amounts during a measurement period not to extend beyond one year of the enactment date. We recognized the provisional impacts related to the one-time transition tax, the revaluation of deferred tax balances and reassessment of the realizability of deferred tax assets and included these estimates in our consolidated financial statements for the year ended December 30, 2017. We completed our analysis within the measurement period in accordance with SAB 118 and did not have a material impact to our consolidated financial statements.

Employee Benefit Plans	12 Months Ended
Employee Benefit Plans	Dec. 29, 2018
Retirement Benefits [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 2018, 2017 and 2016 aggregated $2.0 million, $1.9 million and $0.5 million, respectively.

Segments and Geographic Information

12 Months Ended

Dec. 29, 2018

Segment Reporting [Abstract]

Segments and Geographic Information

Until the acquisition of Cascade Microtech, we operated in one reportable segment relating to the design, development, manufacture and sale of high performance advanced probe cards. We currently operate in two reportable segments consisting of the Probe Cards Segment and the Systems Segment.

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.

The following table summarizes the operating results by reportable segment (dollars in thousands):



	Fiscal 2018
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	434,269		$	95,406		$	—		$	529,675
Gross profit	$	187,320		$	47,074		$	(24,055	)	$	210,339
Gross margin	43.1		%	49.3		%	—		%	39.7		%



	Fiscal 2017
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	454,794		$	93,647		$	—		$	548,441
Gross profit	$	195,903		$	46,647		$	(26,953	)	$	215,597
Gross margin	43.1		%	49.8		%	—		%	39.3		%



	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 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 Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
United States	25.2	%	34.0	%	33.3	%
Taiwan	20.3		17.7		14.9
South Korea	17.2		14.9		17.1
China	14.7		11.1		7.4
Japan	9.4		8.1		10.0
Europe	7.5		8.2		12.9
Asia-Pacific⁽¹⁾	4.9		5.5		4.0
Rest of the world	0.8		0.5		0.4
Total Revenues	100.0	%	100.0	%	100.0	%

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

The following table summarizes revenue by market (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Foundry & Logic	$	258,459	$	313,714	$	237,591
DRAM	135,333		124,685		86,910
Flash	40,477		16,395		13,469
Systems	95,406		93,647		45,911
Total revenues	$	529,675	$	548,441	$	383,881

The following table summarizes revenue by timing of revenue recognition (in thousands):



	Fiscal Year Ended
	December 29, 2018						December 30, 2017						December 31, 2016
	Probe Cards		Systems		Total		Probe Cards		Systems		Total		Probe Cards		Systems		Total
Products transferred at a point in time	$	432,033	$	91,514	523,547		$	452,946	$	90,107	543,053		$	335,988	$	44,048	380,036
Services transferred over time	2,236		3,892		6,128		1,848		3,540		5,388		1,982		1,863		3,845
Total	$	434,269	$	95,406	$	529,675	$	454,794	$	93,647	$	548,441	$	337,970	$	45,911	$	383,881

Long-lived assets, comprised of Property, plant and equipment, net, Goodwill and Intangibles, net, reported based on the location of the asset was as follows (in thousands):



	December 29, 2018		December 30, 2017		December 31, 2016
United States	$	280,405	$	299,574	$	323,369
Europe	26,118		30,922		30,903
Asia-Pacific	4,385		3,662		3,009
Total	$	310,908	$	334,158	$	357,281

Selected Quarterly Financial Data (Unaudited)

12 Months Ended

Dec. 29, 2018

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. 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. 29, 2018⁽¹⁾			Sep. 29, 2018			June 30, 2018			March 31, 2018			Dec. 30, 2017⁽²⁾			Sep. 30, 2017			July 1, 2017			April 1, 2017
	(in thousands, except per share data)
Revenues	$	140,887		$	134,989		$	135,509		$	118,290		$	131,901		$	143,735		$	143,976		$	128,829
Cost of revenues	84,865			82,019			79,291			73,161			83,272			86,105			82,209			81,258
Gross profit	56,022			52,970			56,218			45,129			48,629			57,630			61,767			47,571
Operating Expenses:
Research and development	18,398			18,857			19,675			18,046			18,513			19,338			18,542			17,414
Selling, general and administrative	25,668			24,745			25,232			23,449			24,238			24,010			23,602			22,829
Restructuring	160			—			—			—			481			16			44			269
Total operating expenses	44,226			43,602			44,907			41,495			43,232			43,364			42,188			40,512
Operating income	11,796			9,368			11,311			3,634			5,397			14,266			19,579			7,059
Interest income	404			369			326			257			264			123			93			67
Interest expense	(660		)	(777		)	(910		)	(967		)	(1,045		)	(1,109		)	(1,162		)	(1,174		)
Other income (expense), net	117			121			50			(512		)	(170		)	311			107			(400		)
Income before income taxes	11,657			9,081			10,777			2,412			4,446			13,591			18,617			5,552
Provision (benefit) for income taxes	(73,443		)	1,393			1,654			287			(1,142		)	1,028			1,040			367
Net income	$	85,100		$	7,688		$	9,123		$	2,125		$	5,588		$	12,563		$	17,577		$	5,185
Net income per share:⁽³⁾
Basic	$	1.15		$	0.10		$	0.12		$	0.03		$	0.08		$	0.17		$	0.24		$	0.07
Diluted	$	1.13		$	0.10		$	0.12		$	0.03		$	0.07		$	0.17		$	0.24		$	0.07
Weighted average number of shares used in per share calculations:
Basic	74,108			73,837			73,157			72,826			72,846			72,651			72,200			71,423
Diluted	75,416			74,962			74,533			74,342			74,756			73,885			73,539			72,922


(1)	In the fourth quarter of fiscal 2018, the tax benefit included a $75.8 million benefit from a valuation allowance release against certain U.S. deferred tax assets.


(2)	In the fourth quarter of fiscal 2017, the tax benefit included a $0.7 million benefit from U.S. tax reform and a $0.8 million benefit from refundable AMT tax credits.


(3)	Quarterly net income per share amounts may not add to the yearly totals due to rounding.

New Accounting Pronouncements (Notes)

12 Months Ended

Dec. 29, 2018

Accounting Policies [Abstract]

New Accounting Pronouncements

ASU 2018-15

In August 2018, the Financial Accounting Standard Board ("FASB") issued Accounting Standards Update ("ASU") 2018-15, "Intangibles-Goodwill and Other-Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract." The new guidance clarifies the accounting for implementation costs in cloud computing arrangements. ASU 2018-15 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2019. Early adoption is permitted. ASU 2018-15 should be applied either retrospectively or prospectively to all implementation costs incurred after the date of adoption. We have not yet determined the impact of this standard on our financial statements.

ASU 2017-12

In August 2017, the FASB issued ASU 2017-12, "Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities," which changes the recognition and presentation requirements of hedge accounting, including eliminating the requirement to separately measure and report hedge ineffectiveness and changing the presentation to include all items that affect earnings in the same income statement line item as the hedged item. ASU 2017-12 also provides new alternatives for applying hedge accounting to additional hedging strategies, measuring the hedged item in fair value hedges of interest rate risk, reducing the cost and complexity of applying hedge accounting and reducing the risk of material error correction if a company applies the shortcut method inappropriately. ASU 2017-12 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2018, on a prospective basis. We early adopted ASU 2017-12 on December 31, 2017, the first day of fiscal 2018, resulting in an immaterial adjustment in our accumulated deficit on December 30, 2017.

ASU 2017-09

In May 2017, the FASB issued ASU 2017-09, "Compensation - Stock Compensation (Topic 718) - Scope of Modification Accounting," which provides clarity and reduces both diversity in practice and the cost and complexity when accounting for a change to the terms of a stock-based award. ASU 2017-09 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2017, on a prospective basis. We adopted ASU 2017-09 on December 31, 2017, the first day of fiscal 2018. There were no modifications to any stock-based awards during fiscal 2018.

ASU 2017-04

In January 2017, the FASB issued ASU 2017-04, "Intangibles - Goodwill and Other (Topic 350) - Simplifying the Test for Goodwill Impairment," which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test. An entity should perform its annual, or interim, goodwill impairment test by comparing the fair value of a reporting unit with its carrying amount, and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value, if applicable. The loss recognized should not exceed the total amount of goodwill allocated to the reporting unit. The same impairment test also applies to any reporting unit with a zero or negative carrying amount. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 is effective for fiscal years, including interim periods within those fiscal years, beginning after December 15, 2019, on a prospective basis. Early adoption is permitted for interim or annual goodwill impairment tests performed after January 1, 2017. We early adopted ASU 2017-04 on July 1, 2018, the first day of the third quarter of fiscal 2018. The adoption did not have an effect on our financial position, results of operations or cash flows.

ASU 2017-01

In January 2017, the FASB issued ASU 2017-01, “Business Combinations (Topic 805) - Clarifying the Definition of a Business” which clarifies the definition and provides a more robust framework to use in determining when a set of assets and activities constitutes a business. ASU 2017-01 is intended to provide guidance when evaluating whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. We adopted ASU 2017-01 on December 31, 2017, the first day of fiscal 2018. The adoption did not have an effect on our financial position, results of operations or cash flows.

ASU 2016-18

In November 2016, the FASB issued ASU 2016-18, "Statement of Cash Flows (Topic 230) - Restricted Cash," which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. Therefore, an entity should include amounts generally described as restricted cash or restricted cash equivalents within cash and cash equivalents when reconciling the beginning-of-period and end-of-period total amounts shown on the statement of cash flows. Prior to this ASU, there was no guidance to address how to classify and present changes in restricted cash or restricted cash equivalents. The updated guidance is effective for interim and annual periods beginning after December 15, 2017. We adopted ASU 2016-18 as of December 31, 2017, the first day of fiscal 2018 and retrospectively applied such guidance to our Condensed Consolidated Statements of Cash Flows.

The following table provides a reconciliation of Cash and cash equivalents as previously reported within the Condensed Consolidated Statements of Cash Flows to Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows (in thousands):



	December 30, 2017		December 31, 2016
Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows	$	91,184	$	101,408
Current assets - Restricted cash	372		106
Restricted cash	1,170		1,082
Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows	$	92,726	$	102,596

As of December 29, 2018 and December 30, 2017, Restricted cash was comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases and customer deposits.

ASU 2016-10, ASU 2015-14 and ASU 2014-09

In May 2014, the Financial Accounting Standard Board ("FASB") issued ASU No. 2014-09, "Revenue from Contracts with Customers," ("ASC 606"). ASU 2014-09 requires an entity to recognize revenue to depict the transfer of goods or services to customers in an amount that reflects the consideration to which an entity expects to be entitled in exchange for those goods or services. The guidance also requires expanded disclosures relating to the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. Additionally, qualitative and quantitative disclosures are required about customer contracts, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The standard permits the use of either the retrospective or modified retrospective transition methods. We adopted ASC 606 on December 31, 2017, the first day of fiscal 2018, using the modified retrospective method. We applied ASC 606 to all contracts not completed as of the date of adoption in order to determine any adjustment to the opening balance of retained earnings. Under the modified retrospective adoption method, the comparative financial information has not been restated and continues to be reported under the accounting standards in effect for those periods, ASC 605, "Revenue Recognition", which is also referred to herein as "legacy GAAP."

The adoption of ASC 606 did not have a material impact on our consolidated financial statements as of December 31, 2017. No adjustment was recorded to accumulated deficit as of the adoption date and reported revenue would not have been different under legacy GAAP.

ASU 2016-02, ASU 2018-10 and ASU 2018-11

In February 2016, the FASB issued ASU 2016-02, "Leases (Topic 842)," which requires the recognition of right-of-use assets and lease liabilities for all long-term leases, including operating leases, on the balance sheet. ASU 2016-02 was amended in July 2018 by both ASU 2018-10, "Codification Improvements to Topic 842, Leases," and ASU 2018-11, "Leases (Topic 842): Targeted Improvements." ASU 2016-02 provides additional guidance on the measurement of the right-of-use assets and lease liabilities and will require enhanced disclosures about our leasing arrangements. Under current accounting standards, substantially all of our leases are considered operating leases and, as such, are not recognized on the Consolidated Balance Sheet. This new standard is effective for us beginning on December 30, 2018, with early adoption permitted. As initially issued, the standard required a “modified retrospective” adoption, meaning the standard is applied to leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. As amended, the standard allows an additional transition method that permits a company to use its effective date as the date of initial application, and therefore, not restate comparative prior period financial information. Upon adoption we will use the modified transition method. We are currently assessing the impact on our Consolidated Financial Statements, which includes assessing the discount rate to be applied to these valuations. We expect that the primary impact upon adoption will be the recognition, on a discounted basis, of our minimum commitments under noncancelable operating leases to our Consolidated Balance Sheets resulting in the recording of right-of-use assets in the range of $30.3 million to $35.5 million and lease liabilities in the range of $35.8 million to $40.9 million.

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 29, 2018

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 classify our marketable securities as available-for-sale and, accordingly, report them at fair value with the related unrealized gains and losses included in Accumulated other comprehensive income in our Consolidated Balance Sheets. Any unrealized losses which are considered to be other-than-temporary are recorded in Other income (expense), net, in the Consolidated Statements of Operations. Realized gains and 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.

Foreign Exchange Management

Allowance for Doubtful Accounts

Accounts Receivable and Allowance for Doubtful Accounts

The majority of our accounts receivable are derived from sales to large multinational semiconductor manufacturers throughout the world, are recorded at their invoiced amount and do not bear interest.

Inventories

Inventories are stated at the lower of cost (principally standard cost which approximates actual cost on a first-in, first-out basis) or net realizable value.

Restricted Cash

Restricted cash is comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases, customer deposits, and temporary customs import permits.

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

Revenue by Category: Refer to Note 16 of Notes to Consolidated Financial Statements for further details.

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.

Restructuring Charges

Income Taxes

See Note 14 for additional information, including the Tax Cuts and Jobs Act enacted in December 2017.

Stock-based Compensation

Stock-Based Compensation

See Notes 12 and 13 for additional information.

Net Loss Per Share

Net Income (Loss) Per Share

Fair Value Measurement


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


•	Level 2 valuations utilize significant observable inputs, 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 utilize 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.

We did not have any transfers of assets or liabilities measured at fair value on a recurring basis to or from Level 1, Level 2 or Level 3 during fiscal 2018, 2017 or 2016.

No changes were made to our valuation techniques during fiscal 2018.

Cash Equivalents

The fair value of our cash equivalents is determined based on quoted market prices for similar or identical securities.

Marketable Securities

New Accounting Pronouncements

ASU 2018-15

ASU 2017-12

ASU 2017-09

ASU 2017-04

ASU 2017-01

ASU 2016-18



	December 30, 2017		December 31, 2016
Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows	$	91,184	$	101,408
Current assets - Restricted cash	372		106
Restricted cash	1,170		1,082
Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows	$	92,726	$	102,596

As of December 29, 2018 and December 30, 2017, Restricted cash was comprised primarily of funds held by our foreign subsidiaries for employee obligations, office leases and customer deposits.

ASU 2016-10, ASU 2015-14 and ASU 2014-09

ASU 2016-02, ASU 2018-10 and ASU 2018-11

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 29, 2018

Accounting Policies [Abstract]

Schedules of Concentration of Risk, by Customer

The following customer represented 10% or more of our revenues:



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Intel Corporation	19.0	%	25.9	%	30.1	%

Schedule of Product Warranty Liability Reconciliation

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



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Balance at beginning of year	$	3,662		$	2,972		$	1,116
Warranty reserve from acquisition-Cascade Microtech	—			—			795
Accruals	3,181			8,115			5,254
Settlements	(4,741		)	(7,425		)	(4,193		)
Balance at end of year	$	2,102		$	3,662		$	2,972

Schedule of Allowance for Doubtful Accounts

Activity related to our allowance for doubtful accounts receivable was as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Balance at beginning of year	$	200		$	299		$	284
Charges (reversals) to costs and expenses	(15		)	(99		)	51
Write-offs	—			—			(36		)
Balance at end of year	$	185		$	200		$	299

Schedule of Calculation of Numerator and Denominator in Earnings Per Share

The following table reconciles the shares used in calculating basic net income (loss) per share and diluted net income (loss) per share (in thousands):



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Weighted-average shares used in computing basic net income (loss) per share	73,482	72,292	64,941
Add potentially dilutive securities	1,700	1,947	—
Weighted-average shares used in computing basic and diluted net income (loss) per share	75,182	74,239	64,941

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

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



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Options to purchase common stock	—	—	2,198
Restricted stock units	—	1	3,113
Employee stock purchase plan	—	—	10
Total potentially dilutive securities	—	1	5,321

Schedule of Accumulated Other Comprehensive Loss



	December 29, 2018			December 30, 2017
Unrealized losses on marketable securities	$	(668	)	$	(660	)
Cumulative translation adjustments	918			2,983
Unrealized gains on derivative instruments	367			698
Unrealized gains on the translation of deferred tax assets	163			—
Accumulated other comprehensive income	$	780		$	3,021

Balance Sheet Components (Tables)

12 Months Ended

Dec. 29, 2018

Balance Sheet Components [Abstract]

Schedule of Marketable Securities

Marketable securities consisted of the following (in thousands):



December 29, 2018	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	7,997	$	1	$	(1	)	$	7,997
Commercial paper	2,296		—		(1		)	2,295
Corporate bond	30,833		1		(160		)	30,674
Certificate of deposit	960		—		(3		)	957
Agency securities	8,667		—		(59		)	8,608
	$	50,753	$	2	$	(224	)	$	50,531



December 30, 2017	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value
U.S. Treasuries	$	3,968	$	—	$	(5	)	$	3,963
Commercial paper	3,000		—		—			3,000
Corporate bond	30,785		1		(150		)	30,636
Certificate of deposit	960		—		(3		)	957
Agency securities	10,489		—		(57		)	10,432
	$	49,202	$	1	$	(215	)	$	48,988

Contractual Maturity of Marketable Securities

The contractual maturities of marketable securities were as follows (in thousands):



	December 29, 2018				December 30, 2017
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due in one year or less	$	35,269	$	35,172	$	23,009	$	22,966
Due after one year to five years	15,484		15,359		26,193		26,022
	$	50,753	$	50,531	$	49,202	$	48,988

Schedule of Net Inventory

Inventories consisted of the following (in thousands):



	December 29, 2018		December 30, 2017
Raw materials	$	43,380	$	33,101
Work-in-progress	20,431		20,134
Finished goods	13,895		14,613
	$	77,706	$	67,848

Schedule of Property, Plant and Equipment

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



	December 29, 2018			December 30, 2017
Machinery and equipment	$	192,108		$	183,186
Computer equipment and software	32,906			32,841
Furniture and fixtures	6,478			6,478
Leasehold improvements	75,285			73,978
Sub-total	306,777			296,483
Less: Accumulated depreciation and amortization	(263,102		)	(255,755		)
Net property, plant and equipment	43,675			40,728
Construction-in-progress	10,379			6,026
Total	$	54,054		$	46,754

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):



	December 29, 2018		December 30, 2017
Accrued compensation and benefits	$	15,600	$	18,141
Accrued employee stock purchase plan contributions withheld	3,174		3,279
Accrued warranty	2,102		3,662
Accrued income and other taxes	4,222		3,965
Other accrued expenses	2,633		4,647
	$	27,731	$	33,694

Acquisition (Tables)

12 Months Ended

Dec. 29, 2018

Business Combinations [Abstract]

Schedule of Assets Acquired and Liabilities Assumed

The table below summarizes the assets acquired and liabilities assumed following the adjustments mentioned above (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
Tangible assets acquired	133,050

Deferred revenue	(1,829		)
Accounts payable and accrued liabilities	(23,370		)
Deferred tax liabilities	(48,993		)
Other long-term liabilities	(960		)
Liabilities assumed	(75,152		)
Total tangible assets acquired and liabilities assumed	57,898
Intangible assets	149,753
Goodwill	158,141
Net assets acquired	$	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		N/A
Total intangible assets	$	149,753	4.1

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		N/A
Total intangible assets	$	149,753	4.1

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 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):



	Fiscal Year Ended
	December 31, 2016
Revenues	$	455,713
Net loss	(20,641		)
Net loss per share - basic	(0.27		)
Net loss per share - diluted	(0.27		)

Debt (Tables)

12 Months Ended

Dec. 29, 2018

Debt Disclosure [Abstract]

Schedule of Maturities of Long-term Debt [Table Text Block]

Future principal and interest payments as of December 29, 2018, based on the interest rate in effect at that date were as follows (in thousands):



	Principal		Interest*
Fiscal year:
2019	$	30,000	$	2,190
2020	35,000		556
Total	$	65,000	$	2,746

* Represents interest payment commitment at 4.35% per annum.

Schedule of Debt

Our debt consisted of the following (in thousands):



	December 29, 2018			December 30, 2017
Term loan	$	65,000		$	106,250
Less unamortized issuance costs	(189		)	(579		)
Total debt less issuance costs	$	64,811		$	105,671

Restructuring Charges (Tables)

12 Months Ended

Dec. 29, 2018

Restructuring Charges [Abstract]

Summary of Restructuring Activities

The following table summarizes the activities related to the restructuring actions (in thousands):



	Employee Severance and Benefits			Contract Termination and Other Costs			Stock-based Compensation			Total
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
Restructuring charges	690			11			109			810
Cash payments	(622		)	(109		)	—			(731		)
Non-cash settlements	—			(5		)	(109		)	(114		)
Accrual at December 30, 2017	398			1			—			399
Restructuring charges	20			140			—			160
Cash payments	(398		)	(1		)	—			(399		)
Non-cash settlements	—			(140		)	—			(140		)
Accrual at December 29, 2018	$	20		$	—		$	—		$	20

Impairment of Long-lived Assets (Tables)

12 Months Ended

Dec. 29, 2018

Property, Plant and Equipment Impairment or Disposal [Abstract]

Summary of Impairments of Long-lived Assets

Impairment of long-lived assets was as follows (in thousands):



Fiscal Year Ended
December 29, 2018		December 30, 2017		December 31, 2016
$	—	$	—	$	12,400

Derivative Financial Instruments (Tables)

12 Months Ended

Dec. 29, 2018

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 29, 2018 (in thousands):



Currency	Contract Position	Contract Amount (Local Currency)	Contract Amount (U.S. Dollars)
Euro	Sell	14,843	$	17,082
Japanese Yen	Sell	1,185,877	10,758
Total USD notional amount of outstanding foreign exchange contracts			$	27,840

Schedule of Non-designated Derivative Gains (Losses)

The location and amount of gains (losses) related to non-designated derivative instruments in the Consolidated Statements of Operations were as follows (in thousands):



	Location of Gain (Loss) Recognized on Derivatives	Fiscal Year Ended
Derivatives Not Designated as Hedging Instruments	Location of Gain (Loss) Recognized on Derivatives	December 29, 2018		December 30, 2017			December 31, 2016
Foreign exchange forward contracts	Other expense, net	$	906	$	(2,505	)	$	(1,490	)

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

The impact of the interest rate swaps on the Consolidated Statements of Operations was as follows (in thousands):



	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 )
Fiscal 2018	$	340	Other expense, net	$	721		Other expense, net	$	—
Fiscal 2017	$	287	Other expense, net	$	84		Other expense, net	$	29
Fiscal 2016	$	628	Other expense, net	$	(160	)	Other expense, net	$	51

Fair Value (Tables)

12 Months Ended

Dec. 29, 2018

Fair Value Disclosures [Abstract]

Schedule of Fair Values Measured on Recurring Basis



December 29, 2018	Level 1		Level 2		Total
Assets:
Cash equivalents:
Money market funds	$	1,184	$	—	$	1,184
Marketable securities:
U.S. Treasuries	7,997		—		7,997
Certificates of deposit	—		957		957
Agency securities	—		8,608		8,608
Corporate bonds	—		30,674		30,674
Commercial paper	—		2,295		2,295
	7,997		42,534		50,531
Interest rate swap derivative contracts	—		871		871
Total assets	$	9,181	$	43,405	$	52,586



December 30, 2017	Level 1		Level 2		Total
Assets:
Cash equivalents:
Money market funds	$	1,064	$	—	$	1,064
Corporate bonds	—		774		774
	1,064		774		1,838
Marketable securities:
U.S. Treasuries	3,963		—		3,963
Certificates of deposit	—		957		957
Agency securities	—		10,432		10,432
Corporate bonds	—		30,636		30,636
Commercial paper	—		3,000		3,000
	3,963		45,025		48,988
Foreign exchange derivative contract	—		31		31
Interest rate swap derivative contracts	—		1,043		1,043
Total assets	$	5,027	$	46,873	$	51,900

Goodwill and Intangible Assets (Tables)

12 Months Ended

Dec. 29, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

Goodwill by reportable segment was as follows (in thousands):



	Probe Cards		Systems			Total
Goodwill, gross, as of December 26, 2015	$	30,731	$	—		$	30,731
Additions - Cascade Microtech acquisition	141,751		16,390			158,141
Foreign currency translation	—		(862		)	(862		)
Goodwill, gross, as of December 31, 2016	172,482		15,528			188,010
Foreign currency translation	—		1,910			1,910
Goodwill, gross, as of December 30, 2017	172,482		17,438			189,920
Foreign currency translation	—		(706		)	(706		)
Goodwill, gross, as of December 29, 2018	$	172,482	$	16,732		$	189,214

Schedule of Finite-lived Intangible Assets

Intangible assets were as follows (in thousands):



	December 29, 2018						December 30, 2017
Other Intangible Assets	Gross		Accumulated Amortization		Net		Gross		Accumulated Amortization		Net
Existing developed technologies	$	143,408	$	97,111	$	46,297	$	143,966	$	76,826	$	67,140
Trade name	12,023		9,173		2,850		12,086		5,735		6,351
Customer relationships	40,146		21,653		18,493		40,313		16,320		23,993
Backlog	—		—		—		15,811		15,811		—
	$	195,577	$	127,937	$	67,640	$	212,176	$	114,692	$	97,484

Schedule of Amortization Expense

Amortization expense was included in our Consolidated Statements of Operations as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Cost of revenues	$	20,530	$	22,800	$	30,039
Selling, general and administrative	8,843		8,140		5,388
	$	29,373	$	30,940	$	35,427

Schedule of Remaining Estimated Amortization Expense

The estimated future amortization of intangible assets is as follows (in thousands):



Fiscal Year	Amount
2019	$	26,387
2020	23,377
2021	12,628
2022	3,206
2023	2,042
Total	$	67,640

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 29, 2018

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Operating Lease Payments

Future minimum payments under our non-cancelable operating leases were as follows as of December 29, 2018 (in thousands):



Fiscal year:	Amount
2019	$	6,256
2020	6,522
2021	5,742
2022	4,786
2023	4,355
Thereafter	20,382
Total	$	48,043

Stockholders' Equity (Tables)

12 Months Ended

Dec. 29, 2018

Equity [Abstract]

Schedule of Stock Option Activity

Stock option activity was as follows:



	Outstanding Options
	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life in Years	Aggregate Intrinsic Value
Outstanding at December 30, 2017	659,334		$	8.12
Options exercised	(134,609	)	8.60
Outstanding at December 29, 2018	524,725		$	8.00	3.1	$	3,155,659
Vested and expected to vest at December 29, 2018	524,725		$	8.00	3.1	$	3,155,659
Exercisable at December 29, 2018	401,105		$	7.94	3.0	$	2,435,515

Schedule of Restricted Stock Unit Activity

RSU activity was as follows:



	Number of Shares		Weighted Average Grant Date Fair Value
Restricted stock units at December 30, 2017	3,148,061		$	11.22
Granted	1,551,770		13.79
Vested	(1,287,107	)	10.43
Canceled	(310,498	)	11.66
Restricted stock units at December 29, 2018	3,102,226		12.79

Schedule of Performance Restricted Stock Unit Activity

PRSU activity was as follows:



	Fiscal Year Ended
	December 29, 2018	December 30, 2017	December 31, 2016
Grant Date	August 16, 2018	July 20, 2017	August 19, 2016
Performance period	July 1, 2018 - June 30, 2021	July 1, 2017 - June 30, 2020	April 1, 2016 - March 31, 2019
Number of shares	318,100	333,333	195,000
TSR as-of date	August 16, 2018	July 1, 2017	April 1, 2016
Stock-based compensation	$4.7 million	$4.1 million	$2.0 million

Stock-Based Compensation (Tables)

12 Months Ended

Dec. 29, 2018

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

Schedule of Additional Information Regarding Stock Based Compensation

Certain information regarding our stock-based compensation was as follows (in thousands, except per share amounts):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Weighted average grant date per share fair value of stock options granted	$	—	$	—	$	2.00
Weighted average grant date per share fair value of RSUs granted	13.79		13.20		8.20
Total intrinsic value of stock options exercised	631		5,946		558
Fair value of RSUs vested	17,541		18,339		12,441

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was included in the Consolidated Statement of Operations as follows (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Stock-based compensation expense included in:
Cost of revenues	$	3,525	$	3,539	$	2,518
Research and development	5,398		5,341		3,329
Selling, general and administrative	8,904		7,350		4,875
Restructuring and impairment charges, net	—		109		964
Total stock-based compensation	$	17,827	$	16,339	$	11,686

Schedule of Unrecognized Compensation Expense

Unrecognized stock-based compensation expense at December 29, 2018 consisted of the following (in thousands):

Schedule of Assumptions, Fair Value of Employee Purchase Rights

The following assumptions were used in estimating the fair value of options awarded and Employee Stock Purchase Plan:



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
2012 Equity Incentive Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	—	%	—	%	43.76	%
Risk-free interest rate	—	%	—	%	1.57	%
Expected life (in years)	0		0		5.5

Employee Stock Purchase Plan:
Dividend yield	—	%	—	%	—	%
Expected volatility	44.85%-48.94%		46.20%-46.33%		43.76%-46.48%
Risk-free interest rate	0.83%-2.22%		0.65%-1.15%		0.40%-0.47%
Expected life (in years)	0.5-1.0		0.5-1.0		0.5-1.0

Income Taxes (Tables)

12 Months Ended

Dec. 29, 2018

Income Tax Disclosure [Abstract]

Schedule of Components of Loss Before Income Taxes

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



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
United States	$	20,877	$	31,492	$	(50,947	)
Foreign	13,050		10,714		752
	$	33,927	$	42,206	$	(50,195	)

Schedule of Components of Provision for Income Taxes

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



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Current provision (benefit):
Federal	$	79		$	(2,130	)	$	—
State	388			17			120
Foreign	4,687			4,069			1,804
	5,154			1,956			1,924
Deferred provision (benefit):
Federal	(72,295		)	66			(42,150		)
State	(2,056		)	—			(2,165		)
Foreign	(912		)	(729		)	(1,247		)
	(75,263		)	(663		)	(45,562		)
Total provision (benefit) for income taxes	$	(70,109	)	$	1,293		$	(43,638	)

Schedule of Effective Income Tax Rate Reconciliation



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
U.S. statutory federal tax rate	$	7,125		$	14,772		$	(17,568	)
State taxes, net of federal benefit	778			951			(975		)
Stock-based compensation	(453		)	(1,428		)	1,256
Research and development credits	(3,213		)	(1,979		)	(1,654		)
Foreign taxes at rates different than the U.S.	1,287			(271		)	504
Other permanent differences	152			160			2,048
Global intangible low-taxed income	1,828			—			—
Mandatory deemed repatriation	—			1,655			—
Change in valuation allowance	(75,803		)	(12,207		)	(27,120		)
Other	(1,810		)	(360		)	(129		)
Total	$	(70,109	)	$	1,293		$	(43,638	)

Schedule of Deferred Tax Assets and Liabilities

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



	As of
	December 29, 2018			December 30, 2017
Tax credits	$	39,586		$	35,484
Inventory reserve	10,850			10,763
Other reserves and accruals	5,398			5,667
Non-statutory stock options	2,722			2,642
Depreciation and amortization	1,979			3,677
Net operating loss carryforwards	61,275			70,457
Gross deferred tax assets	121,810			128,690
Valuation allowance	(34,037		)	(109,840		)
Total deferred tax assets	87,773			18,850
Acquired intangibles and fixed assets	(12,667		)	(18,921		)
Unrealized investment gains	(107		)	(109		)
Tax on undistributed earnings	(53		)	(66		)
Total deferred tax liabilities	(12,827		)	(19,096		)
Net deferred tax assets (liabilities)	$	74,946		$	(246	)

Summary of Tax Credit Carryforwards

Tax credits and carryforwards available to us at December 29, 2018 consisted of the following (in thousands):



	Amount		Latest Expiration Date
Federal research and development tax credit	$	33,837	2021-2038
Federal net operating loss carryforwards	201,484		2030-2035
Foreign tax credit carryforwards	1,325		2019-2028
Alternative minimum tax credits	391		Indefinite
California research credits	32,964		Indefinite
Oregon research credits	281		2019-2022
State net operating loss carryforwards	250,873		2024-2036
Singapore net operating loss carryforwards	8,949		Indefinite

Schedule of Unrecognized Tax Benefits

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



	Fiscal Year Ended
	December 29, 2018			December 30, 2017			December 31, 2016
Unrecognized tax benefit, beginning balance	$	18,296		$	17,978		$	17,033
Additions based on tax positions related to the current year	1,677			694			614
Additions based on tax positions from prior years	5,332			—			450
Reductions for tax positions of prior years	(7		)	—			—
Reductions due to lapse of the applicable statute of limitations	(74		)	(376		)	(119		)
Unrecognized tax benefit, ending balance	$	25,224		$	18,296		$	17,978

Interest and penalties recognized as a component of Provision (benefit) for income taxes	$	71		$	67		$	22
Interest and penalties accrued at period end	230			218			209

Segments and Geographic Information (Tables)

12 Months Ended

Dec. 29, 2018

Segment Reporting [Abstract]

Operating Results by Reportable Segments

The following table summarizes the operating results by reportable segment (dollars in thousands):



	Fiscal 2018
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	434,269		$	95,406		$	—		$	529,675
Gross profit	$	187,320		$	47,074		$	(24,055	)	$	210,339
Gross margin	43.1		%	49.3		%	—		%	39.7		%



	Fiscal 2017
	Probe Cards			Systems			Corporate and Other			Total
Revenues	$	454,794		$	93,647		$	—		$	548,441
Gross profit	$	195,903		$	46,647		$	(26,953	)	$	215,597
Gross margin	43.1		%	49.8		%	—		%	39.3		%



	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		%

Summary of Revenue by Geographic Region

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



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
United States	25.2	%	34.0	%	33.3	%
Taiwan	20.3		17.7		14.9
South Korea	17.2		14.9		17.1
China	14.7		11.1		7.4
Japan	9.4		8.1		10.0
Europe	7.5		8.2		12.9
Asia-Pacific⁽¹⁾	4.9		5.5		4.0
Rest of the world	0.8		0.5		0.4
Total Revenues	100.0	%	100.0	%	100.0	%

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

Summary of Revenue by Market

The following table summarizes revenue by market (in thousands):



	Fiscal Year Ended
	December 29, 2018		December 30, 2017		December 31, 2016
Foundry & Logic	$	258,459	$	313,714	$	237,591
DRAM	135,333		124,685		86,910
Flash	40,477		16,395		13,469
Systems	95,406		93,647		45,911
Total revenues	$	529,675	$	548,441	$	383,881

Summary of Revenue by Timing of Recognition

The following table summarizes revenue by timing of revenue recognition (in thousands):



	Fiscal Year Ended
	December 29, 2018						December 30, 2017						December 31, 2016
	Probe Cards		Systems		Total		Probe Cards		Systems		Total		Probe Cards		Systems		Total
Products transferred at a point in time	$	432,033	$	91,514	523,547		$	452,946	$	90,107	543,053		$	335,988	$	44,048	380,036
Services transferred over time	2,236		3,892		6,128		1,848		3,540		5,388		1,982		1,863		3,845
Total	$	434,269	$	95,406	$	529,675	$	454,794	$	93,647	$	548,441	$	337,970	$	45,911	$	383,881

Long-lived Assets by Location

Long-lived assets, comprised of Property, plant and equipment, net, Goodwill and Intangibles, net, reported based on the location of the asset was as follows (in thousands):



	December 29, 2018		December 30, 2017		December 31, 2016
United States	$	280,405	$	299,574	$	323,369
Europe	26,118		30,922		30,903
Asia-Pacific	4,385		3,662		3,009
Total	$	310,908	$	334,158	$	357,281

Selected Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 29, 2018

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. 29, 2018⁽¹⁾			Sep. 29, 2018			June 30, 2018			March 31, 2018			Dec. 30, 2017⁽²⁾			Sep. 30, 2017			July 1, 2017			April 1, 2017
	(in thousands, except per share data)
Revenues	$	140,887		$	134,989		$	135,509		$	118,290		$	131,901		$	143,735		$	143,976		$	128,829
Cost of revenues	84,865			82,019			79,291			73,161			83,272			86,105			82,209			81,258
Gross profit	56,022			52,970			56,218			45,129			48,629			57,630			61,767			47,571
Operating Expenses:
Research and development	18,398			18,857			19,675			18,046			18,513			19,338			18,542			17,414
Selling, general and administrative	25,668			24,745			25,232			23,449			24,238			24,010			23,602			22,829
Restructuring	160			—			—			—			481			16			44			269
Total operating expenses	44,226			43,602			44,907			41,495			43,232			43,364			42,188			40,512
Operating income	11,796			9,368			11,311			3,634			5,397			14,266			19,579			7,059
Interest income	404			369			326			257			264			123			93			67
Interest expense	(660		)	(777		)	(910		)	(967		)	(1,045		)	(1,109		)	(1,162		)	(1,174		)
Other income (expense), net	117			121			50			(512		)	(170		)	311			107			(400		)
Income before income taxes	11,657			9,081			10,777			2,412			4,446			13,591			18,617			5,552
Provision (benefit) for income taxes	(73,443		)	1,393			1,654			287			(1,142		)	1,028			1,040			367
Net income	$	85,100		$	7,688		$	9,123		$	2,125		$	5,588		$	12,563		$	17,577		$	5,185
Net income per share:⁽³⁾
Basic	$	1.15		$	0.10		$	0.12		$	0.03		$	0.08		$	0.17		$	0.24		$	0.07
Diluted	$	1.13		$	0.10		$	0.12		$	0.03		$	0.07		$	0.17		$	0.24		$	0.07
Weighted average number of shares used in per share calculations:
Basic	74,108			73,837			73,157			72,826			72,846			72,651			72,200			71,423
Diluted	75,416			74,962			74,533			74,342			74,756			73,885			73,539			72,922


(1)	In the fourth quarter of fiscal 2018, the tax benefit included a $75.8 million benefit from a valuation allowance release against certain U.S. deferred tax assets.


(2)	In the fourth quarter of fiscal 2017, the tax benefit included a $0.7 million benefit from U.S. tax reform and a $0.8 million benefit from refundable AMT tax credits.


(3)	Quarterly net income per share amounts may not add to the yearly totals due to rounding.

Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of year	$ 200	$ 299	$ 284
Charges (reversals) to costs and expenses	(15)	(99)	51
Write-offs	0	0	(36)
Balance at end of year	$ 185	$ 200	$ 299

Summary of Significant Accounting Policies - Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Aggregate inventory write downs	$ 10,479	$ 9,259	$ 6,631

Summary of Significant Accounting Policies - Property, Plant, and Equipment (Details)	12 Months Ended
	Dec. 29, 2018
Machinery & Equipment \| Minimum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	1 year
Machinery & Equipment \| Maximum
Property, Plant and Equipment [Line Items]
Property, plant, and equipment useful lives	5 years
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 - Intangibles (Details)	12 Months Ended
	Dec. 29, 2018
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	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Intel Corporation \| Sales Revenue
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	19.00%	25.90%	30.10%
Major Customer 1 \| Accounts Receivable
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	27.80%	24.10%
Major Customer 2 \| Accounts Receivable
Concentration Risk [Line Items]
Total revenues attributable to customers greater than 10%	13.00%

Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 26, 2020	Dec. 28, 2019	Dec. 29, 2018	Dec. 30, 2017
Disaggregation of Revenue [Line Items]
Remaining performance obligations			$ 3.4
Contract assets			0.3	$ 1.6
Contract liabilities			5.7	5.7
Revenue recognized on contract liabilities			$ 4.8	$ 4.8
Minimum
Disaggregation of Revenue [Line Items]
Revenue recognition period			1 year
Maximum
Disaggregation of Revenue [Line Items]
Revenue recognition period			3 years
Scenario, Forecast
Disaggregation of Revenue [Line Items]
Remaining performance obligations expected to be recognized	22.30%	77.70%

Summary of Significant Accounting Policies - Warranty Obligations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Movement in Standard Product Warranty Accrual [Roll Forward]
Warranty Accrual beginning balance	$ 3,662	$ 2,972	$ 1,116
Warranty reserve from acquisition-Cascade Microtech	0	0	795
Accruals	3,181	8,115	5,254
Settlements	(4,741)	(7,425)	(4,193)
Warranty Accrual ending balance	$ 2,102	$ 3,662	$ 2,972

Summary of Significant Accounting Policies - Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Restructuring and Related Activities [Abstract]
Restructuring	$ 160	$ 0	$ 0	$ 0	$ 481	$ 16	$ 44	$ 269	$ 160	$ 810	$ 7,288

Summary of Significant Accounting Policies - Net Loss per Share (Details) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Weighted-average shares used in computing basic net loss per share (in shares)	74,108	73,837	73,157	72,826	72,846	72,651	72,200	71,423	73,482	72,292	64,941
Add potentially dilutive securities (in shares)									1,700	1,947	0
Weighted-average shares used in computing basic and diluted net loss per share (in shares)	75,416	74,962	74,533	74,342	74,756	73,885	73,539	72,922	75,182	74,239	64,941

Summary of Significant Accounting Policies - Net Loss Per Share Weighted-Average Dilutive Securities (Details) - shares shares in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	0	1	5,321
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	0	0	2,198
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	0	1	3,113
Employee stock purchase plan
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities (in shares)	0	0	10

Summary of Significant Accounting Policies - Comprehensive Loss (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Accounting Policies [Abstract]
Unrealized losses on marketable securities	$ (668)	$ (660)
Cumulative translation adjustments	918	2,983
Unrealized gains on derivative instruments	367	698
Unrealized gains on the translation of deferred tax assets	163	0
Accumulated other comprehensive income	$ 780	$ 3,021

Balance Sheet Components - Marketable Securities (Details) - USD ($)	Dec. 29, 2018	Dec. 30, 2017
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	$ 50,753,000	$ 49,202,000
Gross Unrealized Gains	2,000	1,000
Gross Unrealized Losses	(224,000)	(215,000)
Fair Value	50,531,000	48,988,000
Continuous loss position of investments	100,000	0
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Due in one year or less - Amortized Cost	35,269,000	23,009,000
Due in one year to five years - Amortized Cost	15,484,000	26,193,000
Amortized Cost	50,753,000	49,202,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Due in one year or less - Fair Value	35,172,000	22,966,000
Due in one year to five years - Fair Value	15,359,000	26,022,000
Fair Value	50,531,000	48,988,000
U.S. Treasuries
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	7,997,000	3,968,000
Gross Unrealized Gains	1,000	0
Gross Unrealized Losses	(1,000)	(5,000)
Fair Value	7,997,000	3,963,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Amortized Cost	7,997,000	3,968,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Fair Value	7,997,000	3,963,000
Commercial paper
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	2,296,000	3,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,000)	0
Fair Value	2,295,000	3,000,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Amortized Cost	2,296,000	3,000,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Fair Value	2,295,000	3,000,000
Corporate bonds
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	30,833,000	30,785,000
Gross Unrealized Gains	1,000	1,000
Gross Unrealized Losses	(160,000)	(150,000)
Fair Value	30,674,000	30,636,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Amortized Cost	30,833,000	30,785,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Fair Value	30,674,000	30,636,000
Certificates of deposit
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	960,000	960,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3,000)	(3,000)
Fair Value	957,000	957,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Amortized Cost	960,000	960,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Fair Value	957,000	957,000
Agency securities (Federal)
Debt Securities, Available-for-sale [Abstract]
Amortized Cost	8,667,000	10,489,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(59,000)	(57,000)
Fair Value	8,608,000	10,432,000
Debt Securities, Available-for-sale, Amortized Cost, Fiscal Year Maturity [Abstract]
Amortized Cost	8,667,000	10,489,000
Debt Securities, Available-for-sale, Maturity, Fair Value, Rolling Maturity [Abstract]
Fair Value	$ 8,608,000	$ 10,432,000

Balance Sheet Components - Inventory (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Balance Sheet Components [Abstract]
Raw materials	$ 43,380	$ 33,101
Work-in-progress	20,431	20,134
Finished goods	13,895	14,613
Inventory, Net	$ 77,706	$ 67,848

Balance Sheet Components - Property Plant and Equipment (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 306,777	$ 296,483
Less: Accumulated depreciation and amortization	(263,102)	(255,755)
Property Plant And Equipment Net, Excludes Construction in Progress	43,675	40,728
Construction-in-progress	10,379	6,026
Property, plant and equipment, net	54,054	46,754
Machinery & Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	192,108	183,186
Computer equipment & Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	32,906	32,841
Furniture & Fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	6,478	6,478
Leasehold Improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 75,285	$ 73,978

Balance Sheet Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 15,600	$ 18,141
Accrued employee stock purchase plan contributions withheld	3,174	3,279
Accrued warranty	2,102	3,662
Accrued income and other taxes	4,222	3,965
Other accrued expenses	2,633	4,647
Total	$ 27,731	$ 33,694

Acquisition - Additional Information (Details)		3 Months Ended	12 Months Ended
Acquisition - Additional Information (Details)	Jun. 24, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 29, 2018 USD ($)	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Fair value of stock issued in connection with the acquisition of Cascade Microtech			$ 0	$ 0	$ 97,079,000
Common Stock
Business Acquisition [Line Items]
Fair value of stock issued in connection with the acquisition of Cascade Microtech					10,000
Cascade Microtech
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual					83,500,000
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
Increases (decreases) to pro-forma net income					$ (20,641,000)
Cascade Microtech \| In Process Research and Development
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired	12,400,000
Impairment of long-lived assets		$ 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. 29, 2018	Dec. 30, 2017	Dec. 31, 2016	Jun. 24, 2016	Dec. 26, 2015
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			$ 133,050
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			(75,152)
Goodwill	$ 189,214	$ 189,920	188,010		$ 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) - Cascade Microtech - USD ($) $ in Thousands	Jun. 24, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Total intangible assets	$ 149,753	$ 149,753
Intangible asset weighted average useful life	4 years 1 month 6 days
In Process Research and Development
Business Acquisition [Line Items]
Indefinite-lived intangible assets acquired	$ 12,400
Developed technologies
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]
Finite-lived intangible assets acquired	$ 23,053
Intangible asset weighted average useful life	6 years 9 months 6 days
Backlog
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]
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 $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) $ / shares
Business Acquisition [Line Items]
Business Combination, Pro Forma Information, Revenue of Acquiree since Acquisition Date, Actual	$ 83,500
Revenues	455,713
Net loss	$ (20,641)
Net loss per share - basic (in dollars per share) \| $ / shares	$ (0.27)
Net loss per share - diluted (in dollars per share) \| $ / shares	$ (0.27)

Debt - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Debt Disclosure [Abstract]
Term loan	$ 65,000	$ 106,250
Less unamortized issuance costs	(189)	(579)
Total	$ 64,811	$ 105,671

Debt - Additional Information (Details)		12 Months Ended
Debt - Additional Information (Details)	Jun. 24, 2016 USD ($)	Dec. 29, 2018 USD ($)	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Stated rate		4.35%
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 \| 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
Repayments of debt		$ 15,000,000	$ 20,000,000	$ 5,000,000

Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
Restructuring Charges (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 399				$ 434	$ 399	$ 434	$ 2
Accrual at December 30, 2017	$ 160	$ 0	$ 0	0	$ 481	$ 16	$ 44	269	160	810	7,288
Accrual at December 29, 2018									(399)	(731)	(5,892)
Non-cash settlements									(140)	(114)	(964)
Restructuring reserve, ending balance	20				399				20	399	434
Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				398				330	398	330	2
Accrual at December 30, 2017									20	690	6,220
Accrual at December 29, 2018									(398)	(622)	(5,892)
Non-cash settlements									0	0	0
Restructuring reserve, ending balance	20				398				20	398	330
Contract Termination and Other Costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				1				104	1	104	0
Accrual at December 30, 2017									140	11	104
Accrual at December 29, 2018									(1)	(109)	0
Non-cash settlements									(140)	(5)	0
Restructuring reserve, ending balance	0				1				0	1	104
Stock-based Compensation
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance				$ 0				$ 0	0	0	0
Accrual at December 30, 2017									0	109	964
Accrual at December 29, 2018									0	0	0
Non-cash settlements									0	(109)	(964)
Restructuring reserve, ending balance	$ 0				$ 0				$ 0	$ 0	$ 0

Impairment of Long-lived Assets - Impairment of Long-lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment Impairment or Disposal [Abstract]
Impairment of long-lived assets	$ 0	$ 0	$ 12,400

Impairment of Long-lived Assets - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Long Lived Assets Held-for-sale [Line Items]
Impairment of intangible assets	$ 0	$ 0
Cascade Microtech \| In Process Research and Development
Long Lived Assets Held-for-sale [Line Items]
Impairment of intangible assets			$ 12,400,000

Derivative Financial Instruments - Foreign Currency Derivatives (Details) - Not Designated as Hedging Instrument - Foreign Exchange Forward € in Thousands, ¥ in Thousands, $ in Thousands	12 Months Ended
	Dec. 29, 2018 USD ($)	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 29, 2018 EUR (€)	Dec. 29, 2018 JPY (¥)
Derivatives, Fair Value [Line Items]
Total USD notional amount of outstanding foreign exchange contracts	$ 27,840
Other expense, net
Derivatives, Fair Value [Line Items]
Foreign exchange forward contracts	906	$ (2,505)	$ (1,490)
Sell \| Euro
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	17,082			€ 14,843
Sell \| Japanese Yen
Derivatives, Fair Value [Line Items]
Derivative asset contract amount	$ 10,758				¥ 1,185,877

Derivative Financial Instruments - Interest Rate Swaps (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016	Jul. 25, 2016
Interest Rate Swap
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset	$ 871	$ 1,043
Interest Rate Swap \| Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative asset	900	1,000
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)	340	287	$ 628
Interest Rate Swap \| Other 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)	721	84	(160)
Amount of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion )	0	$ 29	$ 51
Senior Secured Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 60,000			$ 95,600
Fixed interest rate, derivative				2.939%
LIBOR \| Senior Secured Term Loan
Derivative Instruments, Gain (Loss) [Line Items]
Derivative variable rate basis spread				2.00%

Fair Value (Details) - USD ($)	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		$ 1,838,000
Marketable securities	$ 50,531,000	48,988,000
Total assets	52,586,000	51,900,000
Liabilities measured at fair value	0	0
Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		31,000
Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	871,000	1,043,000
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,184,000	1,064,000
U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	7,997,000	3,963,000
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	957,000	957,000
Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	8,608,000	10,432,000
Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		774,000
Marketable securities	30,674,000	30,636,000
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	2,295,000	3,000,000
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		1,064,000
Marketable securities	7,997,000	3,963,000
Total assets	9,181,000	5,027,000
Level 1 \| Foreign exchange derivative contract
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	0
Level 1 \| Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,184,000	1,064,000
Level 1 \| U.S. Treasuries
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	7,997,000	3,963,000
Level 1 \| Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0	0
Level 1 \| Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0	0
Level 1 \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		0
Marketable securities	0	0
Level 1 \| Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		774,000
Marketable securities	42,534,000	45,025,000
Total assets	43,405,000	46,873,000
Level 2 \| Foreign exchange derivative contract
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		31,000
Level 2 \| Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	871,000	1,043,000
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	0	0
Level 2 \| Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	957,000	957,000
Level 2 \| Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	8,608,000	10,432,000
Level 2 \| Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		774,000
Marketable securities	30,674,000	30,636,000
Level 2 \| Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	2,295,000	3,000,000
Nonrecurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets (liabilities), net	$ 0	$ 0	$ 0

Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 189,920,000	$ 188,010,000	$ 30,731,000
Additions - Cascade Microtech acquisition			158,141,000
Foreign currency translation	(706,000)	1,910,000	(862,000)
Goodwill, ending balance	189,214,000	189,920,000	188,010,000
Goodwill impairments	0
Probe Cards
Goodwill [Roll Forward]
Goodwill, beginning balance	172,482,000	172,482,000	30,731,000
Additions - Cascade Microtech acquisition			141,751,000
Foreign currency translation	0	0	0
Goodwill, ending balance	172,482,000	172,482,000	172,482,000
Systems
Goodwill [Roll Forward]
Goodwill, beginning balance	17,438,000	15,528,000	0
Additions - Cascade Microtech acquisition			16,390,000
Foreign currency translation	(706,000)	1,910,000	(862,000)
Goodwill, ending balance	$ 16,732,000	$ 17,438,000	$ 15,528,000

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Gross	$ 195,577	$ 212,176
Accumulated Amortization	127,937	114,692
Net	67,640	97,484
Existing developed technologies
Finite-Lived Intangible Assets [Line Items]
Gross	143,408	143,966
Accumulated Amortization	97,111	76,826
Net	46,297	67,140
Trade name
Finite-Lived Intangible Assets [Line Items]
Gross	12,023	12,086
Accumulated Amortization	9,173	5,735
Net	2,850	6,351
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross	40,146	40,313
Accumulated Amortization	21,653	16,320
Net	18,493	23,993
Backlog
Finite-Lived Intangible Assets [Line Items]
Gross	0	15,811
Accumulated Amortization	0	15,811
Net	$ 0	$ 0

Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 29,373	$ 30,940	$ 35,427
Finite-Lived Intangible Assets, Net, Amortization Expense, Rolling Maturity [Abstract]
2019	26,387
2020	23,377
2021	12,628
2022	3,206
2023	2,042
Total	67,640
Cost of Sales
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	20,530	22,800	30,039
Selling, General and Administrative Expenses
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 8,843	$ 8,140	$ 5,388

Goodwill and Intangible Assets - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 0	$ 0
Cascade Microtech \| In Process Research and Development
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets			$ 12,400,000

Commitments and Contingencies - Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 8.4	$ 7.9	$ 6.5

Commitments and Contingencies - Operating Leases (Details) $ in Thousands	Dec. 29, 2018 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019	$ 6,256
2020	6,522
2021	5,742
2022	4,786
2023	4,355
Thereafter	20,382
Total	$ 48,043

Commitments and Contingencies - Legal Matters (Details) $ in Millions	Aug. 25, 2017 USD ($)
California Wage Law
Loss Contingencies [Line Items]
Amount of settlement	$ 1.5

Stockholders' Equity - Preferred Stock (Details) - $ / shares	Dec. 29, 2018	Dec. 30, 2017
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. 29, 2018	Dec. 30, 2017	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		$ 18,970,000
Purchase and retirement of common stock	0	$ (18,970,000)	$ 0
Remaining available for future repurchases	$ 6,000,000
Common Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount					$ 25,000,000	$ 25,000,000.0
Stock repurchased during the period (in shares)		1,367,617		1,013,162
Stock repurchased during the period, amount				$ 8,200,000

Stockholders' Equity - Equity Incentive Plans (Details) - Equity Incentive Plan	12 Months Ended
	Dec. 29, 2018 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for issuance (in shares)	17,900,000.00
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	4,900,000.0
Stock option vesting period	3 years
Term of options granted	7 years
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option vesting period	3 years

Stockholders' Equity - Stock Options (Details) - Equity Incentive Plan	12 Months Ended
	Dec. 29, 2018 USD ($) $ / shares shares
Number of Shares
Number of Shares, Outstanding (in shares) \| shares	659,334
Number of Shares, Options exercised (in shares) \| shares	(134,609)
Number of Shares, Outstanding (in shares) \| shares	524,725
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding (in USD per share) \| $ / shares	$ 8.12
Weighted Average Exercise Price, Options exercised (in USD per share) \| $ / shares	8.60
Weighted Average Exercise Price, Outstanding (in USD per share) \| $ / shares	$ 8.00
Vested and Expected to Vest
Number of Shares, Vested and expected to vest (in shares) \| shares	524,725
Weighted Average Exercise Price, Vested and expected to vest (in USD per share) \| $ / shares	$ 8.00
Weighted Average Remaining Contractual Life, Vested and expected to vest	3 years 1 month 17 days
Aggregate Intrinsic Value, Vested and expected to vest \| $	$ 3,155,659
Additional Disclosures
Number of Shares, Exercisable (in shares) \| shares	401,105
Weighted Average Exercise Price, Exercisable (in USD per share) \| $ / shares	$ 7.94
Weighted Average Remaining Contractual Life, Outstanding	3 years 1 month 17 days
Aggregate Intrinsic Value, Outstanding \| $	$ 3,155,659
Weighted Average Remaining Contractual Life, Exercisable	3 years 18 days
Aggregate Intrinsic Value, Exercisable \| $	$ 2,435,515

Stockholders' Equity - Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
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, Granted (in USD per share)	$ 13.79	$ 13.20	$ 8.20
Performance Restricted Stock Units
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)	318,100,000,000	333,333,000,000	195,000,000
Stock-based compensation expense	$ 4.7	$ 4.1	$ 2.0
Equity Incentive Plan \| Restricted Stock Units
Number of Shares
Number of Shares, Restricted stock units, beginning balance (in shares)	3,148,061
Number of Shares, Granted (in shares)	1,551,770
Number of Shares, Vested (in shares)	(1,287,107)
Number of Shares, Canceled (in shares)	(310,498)
Number of Shares, Restricted stock units, ending balance (in shares)	3,102,226	3,148,061
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)	$ 11.22
Weighted Average Grant Date Fair Value, Granted (in USD per share)	13.79
Weighted Average Grant Date Fair Value, Vested (in USD per share)	10.43
Weighted Average Grant Date Fair Value, Canceled (in USD per share)	11.66
Weighted Average Grant Date Fair Value, Restricted stock units, ending balance(in USD per share)	$ 12.79	$ 11.22
Minimum \| Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Performance period	2 years
Maximum \| Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Performance period	3 years

Stockholders' Equity - Employee Stock Purchase Plan (Details)	12 Months Ended
	Dec. 29, 2018 purchase_period $ / 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 shares authorized for issuance (in shares)	7,000,000
Number of purchase periods, 12 months offering period \| purchase_period	2
Number of purchase periods, 6 months offering period \| purchase_period	1
Issuance of common stock under the Employee Stock Purchase Plan (in shares)	610,297
Weighted average exercise price, exercisable (in USD per share) \| $ / shares	$ 12.84
Weighted average discount (in USD per share) \| $ / shares	$ 2.82
Shares available for grant (in shares)	3,201,493

Stock-Based Compensation - Stock-based compensation details (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date per share fair value of RSUs granted	$ 13.79	$ 13.20	$ 8.20
Total intrinsic value of stock options exercised	$ 631	$ 5,946	$ 558
Fair value of RSUs vested	$ 17,541	$ 18,339	$ 12,441
Equity Incentive Plan \| Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date per share fair value of stock options granted	$ 0.00	$ 0.00	$ 2.00

Stock-Based Compensation - Stock-based Compensation Expense (Details) - Employee Stock - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation, net of tax	$ 17,827	$ 16,339	$ 11,686
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	3,525	3,539	2,518
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	5,398	5,341	3,329
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	8,904	7,350	4,875
Restructuring Charges
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and impairment charges, net	$ 0	$ 109	$ 964

Stock-Based Compensation - Unrecognized Stock-Based Compensation (Details) $ in Thousands	12 Months Ended
	Dec. 29, 2018 USD ($)
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation - options	$ 53
Weighted Average Recognition Period (Years)	1 month 6 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation - non-options	$ 29,871
Weighted Average Recognition Period (Years)	2 years 1 month 6 days
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation - non-options	$ 243
Weighted Average Recognition Period (Years)	1 month 6 days

Stock-Based Compensation - Valuation Assumptions (Details)	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Stock Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected volatility	0.00%	0.00%	43.76%
Risk-free interest rate	0.00%	0.00%	1.57%
Expected term (in years)	0 years	0 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%
Minimum \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	44.85%	46.20%	43.76%
Risk-free interest rate	0.83%	0.65%	0.40%
Expected term (in years)	6 months	6 months	6 months
Maximum \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility	48.94%	46.33%	46.48%
Risk-free interest rate	2.22%	1.15%	0.47%
Expected term (in years)	1 year	1 year	1 year

Income Taxes - Components of Loss Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Extraordinary Items, Noncontrolling Interest [Abstract]
United States									$ 20,877	$ 31,492	$ (50,947)
Foreign									13,050	10,714	752
Income (loss) before income taxes	$ 11,657	$ 9,081	$ 10,777	$ 2,412	$ 4,446	$ 13,591	$ 18,617	$ 5,552	$ 33,927	$ 42,206	$ (50,195)

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Current provision (benefit):
Federal									$ 79	$ (2,130)	$ 0
State									388	17	120
Foreign									4,687	4,069	1,804
Total current provision (benefit)									5,154	1,956	1,924
Deferred provision (benefit):
Federal									(72,295)	66	(42,150)
State									(2,056)	0	(2,165)
Foreign									(912)	(729)	(1,247)
Total deferred provision (benefit)									(75,263)	(663)	(45,562)
Total provision (benefit) from income taxes	$ (73,443)	$ 1,393	$ 1,654	$ 287	$ (1,142)	$ 1,028	$ 1,040	$ 367	$ (70,109)	$ 1,293	$ (43,638)

Income Taxes - Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal statutory rate					21.00%				21.00%	35.00%
Income Tax Reconciliation
U.S. statutory federal tax rate									$ 7,125	$ 14,772	$ (17,568)
State taxes, net of federal benefit									778	951	(975)
Stock-based compensation									(453)	(1,428)	1,256
Research and development credits									(3,213)	(1,979)	(1,654)
Foreign taxes at rates different than the U.S.									1,287	(271)	504
Other permanent differences									152	160	2,048
Global intangible low-taxed income									1,828	0	0
Mandatory deemed repatriation									0	1,655	0
Change in valuation allowance									(75,803)	(12,207)	(27,120)
Other									(1,810)	(360)	(129)
Total provision (benefit) from income taxes	$ (73,443)	$ 1,393	$ 1,654	$ 287	$ (1,142)	$ 1,028	$ 1,040	$ 367	$ (70,109)	$ 1,293	$ (43,638)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 29, 2018	Dec. 30, 2017
Components of Deferred Tax Assets and Liabilities [Abstract]
Tax credits	$ 39,586	$ 35,484	$ 39,586	$ 35,484
Inventory reserve	10,850	10,763	10,850	10,763
Other reserves and accruals	5,398	5,667	5,398	5,667
Non-statutory stock options	2,722	2,642	2,722	2,642
Depreciation and amortization	1,979	3,677	1,979	3,677
Net operating loss carryforwards	61,275	70,457	61,275	70,457
Gross deferred tax assets	121,810	128,690	121,810	128,690
Valuation allowance	(34,037)	(109,840)	(34,037)	(109,840)
Total deferred tax assets	87,773	18,850	87,773	18,850
Acquired intangibles and fixed assets	(12,667)	(18,921)	(12,667)	(18,921)
Unrealized investment gains	(107)	(109)	(107)	(109)
Tax on undistributed earnings	(53)	(66)	(53)	(66)
Total deferred tax liabilities	(12,827)	(19,096)	(12,827)	(19,096)
Net deferred tax assets	74,946		74,946
Net deferred tax liabilities		$ (246)		$ (246)
Decrease in valuation allowance	75,800		75,800
Valuation allowance	$ 34,000		$ 34,000
Federal statutory rate		21.00%	21.00%	35.00%
Reduction in deferred tax asset, tax act				$ 31,300

Income Taxes - Tax Credits and Carryforwards (Details) $ in Thousands	Dec. 29, 2018 USD ($)
California
Operating Loss Carryforwards [Line Items]
Research credits	$ 32,964
Oregon
Operating Loss Carryforwards [Line Items]
Research credits	281
Singapore
Operating Loss Carryforwards [Line Items]
Singapore net operating loss carryforwards	8,949
Federal
Operating Loss Carryforwards [Line Items]
Federal research and development tax credit	33,837
Net operating loss carryforwards	201,484
Foreign tax credit carryforwards	1,325
Alternative minimum tax credits	391
State
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 250,873

Income Taxes - Undistributed Earnings (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	$ 18,400
Deferred tax liabilities on undistributed earnings	53	$ 66
Non-US
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	12,000
United States
Income Tax Contingency [Line Items]
Repatriation of earnings of foreign subsidiaries	$ 6,400

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit, beginning balance	$ 18,296	$ 17,978	$ 17,033
Additions based on tax positions related to the current year	1,677	694	614
Additions based on tax positions from prior years	5,332	0	450
Reductions for tax positions of prior years	(7)	0	0
Reductions due to lapse of the applicable statute of limitations	(74)	(376)	(119)
Unrecognized tax benefit, ending balance	25,224	18,296	17,978
Interest and penalties recognized as a component of Provision (benefit) for income taxes	71	67	0
Interest and penalties accrued at period end	230	$ 218	$ 209
Tax-effected unrecognized tax benefits	$ 12,300

Income Taxes - Tax Cuts and Jobs Act of 2017 (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 30, 2017	Dec. 29, 2018	Dec. 30, 2017
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%	35.00%
Release of valuation allowance			$ 800
Provisional income inclusion for deemed repatriation			15,700
Deferred tax liabilities on undistributed earnings	$ 66	$ 53	$ 66

Employee Benefit Plans (Details) $ in Millions	12 Months Ended
Employee Benefit Plans (Details) $ in Millions	Dec. 29, 2018 USD ($) plan	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Retirement Benefits [Abstract]
Number of benefit plans \| plan	1,000
Cost recognized under defined contribution plans \| $	$ 2.0	$ 1.9	$ 0.5

Segments and Geographic Information - Operating Results By Segment (Details) $ in Thousands		3 Months Ended								12 Months Ended
	Jun. 23, 2016 segment	Dec. 29, 2018 USD ($)	Sep. 29, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jul. 01, 2017 USD ($)	Apr. 01, 2017 USD ($)	Dec. 29, 2018 USD ($) segment	Dec. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting [Abstract]
Number of reportable segments \| segment	1									2
Segment Reporting Information [Line Items]
Revenues		$ 140,887	$ 134,989	$ 135,509	$ 118,290	$ 131,901	$ 143,735	$ 143,976	$ 128,829	$ 529,675	$ 548,441	$ 383,881
Gross profit		$ 56,022	$ 52,970	$ 56,218	$ 45,129	$ 48,629	$ 57,630	$ 61,767	$ 47,571	$ 210,339	$ 215,597	$ 102,682
Gross margin										39.70%	39.30%	26.70%
Probe Cards
Segment Reporting Information [Line Items]
Revenues										$ 434,269	$ 454,794	$ 337,970
Systems
Segment Reporting Information [Line Items]
Revenues										95,406	93,647	45,911
Operating Segments \| Probe Cards
Segment Reporting Information [Line Items]
Revenues										434,269	454,794	337,970
Gross profit										$ 187,320	$ 195,903	$ 121,407
Gross margin										43.10%	43.10%	35.90%
Operating Segments \| Systems
Segment Reporting Information [Line Items]
Revenues										$ 95,406	$ 93,647	$ 45,911
Gross profit										$ 47,074	$ 46,647	$ 23,925
Gross margin										49.30%	49.80%	52.10%
Corporate and Other
Segment Reporting Information [Line Items]
Revenues										$ 0	$ 0	$ 0
Gross profit										$ (24,055)	$ (26,953)	$ (42,650)
Gross margin										0.00%	0.00%	0.00%

Segments and Geographic Information - Revenue by Country (Details) - Geographic Concentration Risk - Sales Revenue	12 Months Ended
	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Product Information [Line Items]
Total Revenues	100.00%	100.00%	100.00%
United States
Product Information [Line Items]
Total Revenues	25.20%	34.00%	33.30%
Taiwan
Product Information [Line Items]
Total Revenues	20.30%	17.70%	14.90%
South Korea
Product Information [Line Items]
Total Revenues	17.20%	14.90%	17.10%
China
Product Information [Line Items]
Total Revenues	14.70%	11.10%	7.40%
Japan
Product Information [Line Items]
Total Revenues	9.40%	8.10%	10.00%
Europe
Product Information [Line Items]
Total Revenues	7.50%	8.20%	12.90%
Asia-Pacific
Product Information [Line Items]
Total Revenues	4.90%	5.50%	4.00%
Rest of the world
Product Information [Line Items]
Total Revenues	0.80%	0.50%	0.40%

Segments and Geographic Information - Revenue by Product Group (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Revenue from External Customers [Line Items]
Revenues	$ 140,887	$ 134,989	$ 135,509	$ 118,290	$ 131,901	$ 143,735	$ 143,976	$ 128,829	$ 529,675	$ 548,441	$ 383,881
Foundry & Logic
Revenue from External Customers [Line Items]
Revenues									258,459	313,714	237,591
DRAM
Revenue from External Customers [Line Items]
Revenues									135,333	124,685	86,910
Flash
Revenue from External Customers [Line Items]
Revenues									40,477	16,395	13,469
Systems
Revenue from External Customers [Line Items]
Revenues									$ 95,406	$ 93,647	$ 45,911

Segments and Geographic Information - Revenue by Timing of Recognition (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues	$ 140,887	$ 134,989	$ 135,509	$ 118,290	$ 131,901	$ 143,735	$ 143,976	$ 128,829	$ 529,675	$ 548,441	$ 383,881
Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									523,547	543,053	380,036
Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									6,128	5,388	3,845
Probe Cards
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									434,269	454,794	337,970
Probe Cards \| Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									432,033	452,946	335,988
Probe Cards \| Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									2,236	1,848	1,982
Systems
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									95,406	93,647	45,911
Systems \| Products transferred at a point in time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									91,514	90,107	44,048
Systems \| Services transferred over time
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenues									$ 3,892	$ 3,540	$ 1,863

Segments and Geographic Information - Long-Lived Assets by Geographical Location (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Long-Lived Assets [Line Items]
Long-lived assets	$ 310,908	$ 334,158	$ 357,281
United States
Long-Lived Assets [Line Items]
Long-lived assets	280,405	299,574	323,369
Europe
Long-Lived Assets [Line Items]
Long-lived assets	26,118	30,922	30,903
Asia-Pacific
Long-Lived Assets [Line Items]
Long-lived assets	$ 4,385	$ 3,662	$ 3,009

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 29, 2018	Sep. 29, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 30, 2017	Sep. 30, 2017	Jul. 01, 2017	Apr. 01, 2017	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Quarterly Financial Data [Abstract]
Revenues	$ 140,887	$ 134,989	$ 135,509	$ 118,290	$ 131,901	$ 143,735	$ 143,976	$ 128,829	$ 529,675	$ 548,441	$ 383,881
Cost of revenues	84,865	82,019	79,291	73,161	83,272	86,105	82,209	81,258	319,336	332,844	281,199
Gross profit	56,022	52,970	56,218	45,129	48,629	57,630	61,767	47,571	210,339	215,597	102,682
Operating expenses:
Research and development	18,398	18,857	19,675	18,046	18,513	19,338	18,542	17,414	74,976	73,807	57,453
Selling, general and administrative	25,668	24,745	25,232	23,449	24,238	24,010	23,602	22,829	99,094	94,679	73,444
Restructuring	160	0	0	0	481	16	44	269	160	810	7,288
Total operating expenses	44,226	43,602	44,907	41,495	43,232	43,364	42,188	40,512	174,230	169,296	150,589
Operating income	11,796	9,368	11,311	3,634	5,397	14,266	19,579	7,059	36,109	46,301	(47,907)
Interest income	404	369	326	257	264	123	93	67	1,356	548	327
Interest expense	(660)	(777)	(910)	(967)	(1,045)	(1,109)	(1,162)	(1,174)	(3,314)	(4,491)	(2,391)
Other expense, net	117	121	50	(512)	(170)	311	107	(400)	(224)	(152)	(224)
Income (loss) before income taxes	11,657	9,081	10,777	2,412	4,446	13,591	18,617	5,552	33,927	42,206	(50,195)
Provision (benefit) for income taxes	(73,443)	1,393	1,654	287	(1,142)	1,028	1,040	367	(70,109)	1,293	(43,638)
Net income (loss)	$ 85,100	$ 7,688	$ 9,123	$ 2,125	$ 5,588	$ 12,563	$ 17,577	$ 5,185	$ 104,036	$ 40,913	$ (6,557)
Net income (loss) per share:
Basic (in USD per share)	$ 1.15	$ 0.10	$ 0.12	$ 0.03	$ 0.08	$ 0.17	$ 0.24	$ 0.07	$ 1.42	$ 0.57	$ (0.10)
Diluted (in USD per share)	$ 1.13	$ 0.10	$ 0.12	$ 0.03	$ 0.07	$ 0.17	$ 0.24	$ 0.07	$ 1.38	$ 0.55	$ (0.10)
Weighted-average number of shares used in per share calculations:
Basic (in shares)	74,108	73,837	73,157	72,826	72,846	72,651	72,200	71,423	73,482	72,292	64,941
Diluted (in shares)	75,416	74,962	74,533	74,342	74,756	73,885	73,539	72,922	75,182	74,239	64,941
Condensed Income Statements, Captions [Line Items]
Decrease in valuation allowance	$ 75,800								$ 75,800
Benefit from U.S. tax reform					$ 700
Benefit for income taxes	$ 73,443	$ (1,393)	$ (1,654)	$ (287)	1,142	$ (1,028)	$ (1,040)	$ (367)	$ 70,109	$ (1,293)	$ 43,638
Alternative Minimum Tax Credit
Operating expenses:
Provision (benefit) for income taxes					(800)
Condensed Income Statements, Captions [Line Items]
Benefit for income taxes					$ 800

New Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 30, 2018	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016	Dec. 26, 2015
Accounting Policies [Abstract]
Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows		$ 98,472	$ 91,184	$ 101,408
Current assets - Restricted cash		849	372	106
Restricted cash		1,225	1,170	1,082
Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows		$ 100,546	$ 92,726	$ 102,596	$ 146,699
Subsequent Event \| Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	$ 30,300
Lease liabilities	35,800
Subsequent Event \| Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Right-of-use assets	35,500
Lease liabilities	$ 40,900