FormFactor (FORM) 10-Q 6 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 29, 2018	Oct. 31, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	FORMFACTOR INC.
Entity Central Index Key	1,039,399
Current Fiscal Year End Date	--12-29
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Sep. 29, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Common Stock, Shares Outstanding		74,102,335

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Current assets:
Cash and cash equivalents	$ 91,990	$ 91,184
Marketable securities	50,109	48,988
Accounts receivable, net of allowance for doubtful accounts of $200 and $200	88,869	81,515
Inventories, net	81,538	67,848
Restricted cash	129	372
Refundable income taxes	1,320	2,242
Prepaid expenses and other current assets	15,716	13,705
Total current assets	329,671	305,854
Restricted cash	1,034	1,170
Property, plant and equipment, net of accumulated depreciation of $260,607 and $255,755	52,857	46,754
Goodwill	189,427	189,920
Intangibles, net	75,278	97,484
Deferred tax assets	3,042	3,133
Other assets	1,163	2,259
Total assets	652,472	646,574
Current liabilities:
Accounts payable	49,668	35,046
Accrued liabilities	24,877	33,694
Current portion of term loan, net of unamortized issuance cost of $189 and $307	26,061	18,443
Deferred revenue	4,795	4,978
Total current liabilities	105,401	92,161
Term loan, less current portion, net of unamortized issuance cost of $57 and $272	46,193	87,228
Deferred tax liabilities	3,290	3,379
Deferred rent and other liabilities	7,537	5,169
Total liabilities	162,421	187,937
Stockholders’ equity:
Preferred stock, $0.001 par value: 10,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.001 par value: 250,000,000 shares authorized; 74,101,623 and 72,532,176 shares issued and outstanding	75	73
Additional paid-in capital	857,505	843,116
Accumulated other comprehensive income	1,158	3,021
Accumulated deficit	(368,687)	(387,573)
Total stockholders’ equity	490,051	458,637
Total liabilities and stockholders’ equity	$ 652,472	$ 646,574

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 200	$ 200
Accumulated depreciation	260,607	255,755
Debt Issuance Costs, Current, Net	189	307
Debt Issuance Costs, Noncurrent, Net	$ 57	$ 272
Preferred stock, par value (In dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (In shares)	10,000,000	10,000,000
Preferred stock, shares issued (In shares)	0	0
Preferred stock, shares outstanding (In shares)	0	0
Common stock, par value (In dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (In shares)	250,000,000	250,000,000
Common stock, shares issued (In shares)	74,101,623	72,532,176
Common stock, shares outstanding (In shares)	74,101,623	72,532,176

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Income Statement [Abstract]
Revenues	$ 134,989	$ 143,735	$ 388,788	$ 416,540
Cost of revenues	82,019	86,105	234,471	249,572
Gross profit	52,970	57,630	154,317	166,968
Operating expenses:
Research and development	18,857	19,338	56,578	55,294
Selling, general and administrative	24,745	24,010	73,426	70,441
Restructuring	0	16	0	329
Total operating expenses	43,602	43,364	130,004	126,064
Operating income	9,368	14,266	24,313	40,904
Interest income	369	123	952	283
Interest expense	(777)	(1,109)	(2,654)	(3,446)
Other income (expense), net	121	311	(341)	19
Income before income taxes	9,081	13,591	22,270	37,760
Provision for income taxes	1,393	1,028	3,334	2,435
Net income	$ 7,688	$ 12,563	$ 18,936	$ 35,325
Net income per share:
Basic (In dollars per share)	$ 0.10	$ 0.17	$ 0.26	$ 0.49
Diluted (In dollars per share)	$ 0.10	$ 0.17	$ 0.25	$ 0.48
Weighted-average number of shares used in per share calculations:
Basic (In shares)	73,837	72,651	73,273	72,103
Diluted (In shares)	74,962	73,885	74,628	73,540

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 7,688	$ 12,563	$ 18,936	$ 35,325
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	(449)	1,540	(1,732)	5,769
Unrealized gains (losses) on available-for-sale marketable securities	50	(15)	(84)	(37)
Unrealized gains (losses) on derivative instruments	(134)	(36)	(47)	4
Other comprehensive income (loss), net of tax	(533)	1,489	(1,863)	5,736
Comprehensive income	$ 7,155	$ 14,052	$ 17,073	$ 41,061

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (In shares) at Dec. 31, 2016		70,907,847,000
Beginning balance at Dec. 31, 2016	$ 401,056	$ 71	$ 833,341	$ (3,740)	$ (428,616)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the Employee Stock Purchase Plan (In shares)		655,961,000
Issuance of common stock under the Employee Stock Purchase Plan	5,695	$ 1	5,694
Issuance of common stock pursuant to exercise of options for cash (In shares)		1,431,767,000
Issuance of common stock pursuant to exercise of options for cash	13,413	$ 1	13,412
Issuance of common stock pursuant to vesting of restricted stock units (In shares)		845,063,000
Issuance of common stock pursuant to vesting of restricted stock units	(6,618)	$ 1	(6,619)
Purchase and retirement of common stock (In shares)		(867,620,000)
Purchase and retirement of common stock	(10,964)	$ (1)	(10,963)
Stock-based compensation	11,207		11,207
Accounting standard adoptions and adjustments	0		(130)		130
Components of other comprehensive income (loss):
Unrealized gain on marketable securities, net of tax	(37)			(37)
Currency translation adjustments	5,769			5,769
Currency translation adjustments	4			4
Net income	35,325				35,325
Ending balance (In shares) at Sep. 30, 2017		72,973,018,000
Ending balance at Sep. 30, 2017	454,850	$ 73	845,942	1,996	(393,161)
Beginning balance (In shares) at Jul. 01, 2017		72,346,116,000
Beginning balance at Jul. 01, 2017	434,607	$ 73	839,751	507	(405,724)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the Employee Stock Purchase Plan (In shares)		258,937,000
Issuance of common stock under the Employee Stock Purchase Plan	2,795	$ 0	2,795
Issuance of common stock pursuant to exercise of options for cash (In shares)		178,250,000
Issuance of common stock pursuant to exercise of options for cash	1,827	$ 0	1,827
Issuance of common stock pursuant to vesting of restricted stock units (In shares)		257,015,000
Issuance of common stock pursuant to vesting of restricted stock units	(2,156)		(2,156)
Purchase and retirement of common stock (In shares)		(67,300,000)
Purchase and retirement of common stock	(831)		(831)
Stock-based compensation	4,556		4,556
Components of other comprehensive income (loss):
Unrealized gain on marketable securities, net of tax	(15)			(15)
Currency translation adjustments	1,540			1,540
Currency translation adjustments	(36)			(36)
Net income	12,563				12,563
Ending balance (In shares) at Sep. 30, 2017		72,973,018,000
Ending balance at Sep. 30, 2017	$ 454,850	$ 73	845,942	1,996	(393,161)
Beginning balance (In shares) at Dec. 30, 2017	72,532,176	72,532,176,000
Beginning balance at Dec. 30, 2017	$ 458,637	$ 73	843,116	3,021	(387,573)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the Employee Stock Purchase Plan (In shares)		610,297,000
Issuance of common stock under the Employee Stock Purchase Plan	6,662	$ 1	6,661
Issuance of common stock pursuant to exercise of options for cash (In shares)		105,610,000
Issuance of common stock pursuant to exercise of options for cash	1,049		1,049
Issuance of common stock pursuant to vesting of restricted stock units (In shares)		853,540,000
Issuance of common stock pursuant to vesting of restricted stock units	(5,693)	$ 1	(5,694)
Stock-based compensation	12,373		12,373
Accounting standard adoptions and adjustments	(50)				(50)
Components of other comprehensive income (loss):
Unrealized gain on marketable securities, net of tax	(84)			(84)
Currency translation adjustments	(1,732)			(1,732)
Currency translation adjustments	(47)			(47)
Net income	$ 18,936				18,936
Ending balance (In shares) at Sep. 29, 2018	74,101,623	74,101,623,000
Ending balance at Sep. 29, 2018	$ 490,051	$ 75	857,505	1,158	(368,687)
Beginning balance (In shares) at Jun. 30, 2018		73,358,108,000
Beginning balance at Jun. 30, 2018	478,668	$ 74	853,278	1,691	(376,375)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the Employee Stock Purchase Plan (In shares)		268,627,000
Issuance of common stock under the Employee Stock Purchase Plan	2,957		2,957
Issuance of common stock pursuant to vesting of restricted stock units (In shares)		474,888,000
Issuance of common stock pursuant to vesting of restricted stock units	(3,240)	$ 1	(3,241)
Stock-based compensation	4,511		4,511
Components of other comprehensive income (loss):
Unrealized gain on marketable securities, net of tax	50			50
Currency translation adjustments	(449)			(449)
Currency translation adjustments	(134)			(134)
Net income	$ 7,688				7,688
Ending balance (In shares) at Sep. 29, 2018	74,101,623	74,101,623,000
Ending balance at Sep. 29, 2018	$ 490,051	$ 75	$ 857,505	$ 1,158	$ (368,687)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 18,936	$ 35,325
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	10,494	10,046
Amortization	21,876	23,509
Accretion of discount on investments	21	22
Stock-based compensation expense	12,421	11,279
Amortization of debt issuance costs	333	482
Deferred income tax provision	70	122
Recovery of doubtful accounts receivable	0	(97)
Provision for excess and obsolete inventories	7,414	6,899
Acquired inventory step-up amortization	0	484
Loss on disposal of long-lived assets	264	101
(Gain) loss on derivative instruments	0	(18)
Foreign currency transaction losses (gains)	409	(1,957)
Changes in assets and liabilities:
Accounts receivable, net	(7,569)	(17,097)
Inventories, net	(21,806)	(14,270)
Prepaid expenses and other current assets	(1,874)	1,140
Refundable income taxes	933	(440)
Other assets	697	823
Accounts payable	10,425	3,040
Accrued liabilities	(8,882)	(1,048)
Income tax payable	(248)	(97)
Deferred rent and other liabilities	2,445	101
Deferred revenues	(221)	1,517
Net cash provided by operating activities	46,138	59,866
Cash flows from investing activities:
Acquisition of property, plant and equipment	(12,326)	(13,918)
Proceeds from sale of a subsidiary	67	48
Proceeds from sale of property, plant and equipment	23	0
Purchases of marketable securities	(18,984)	(27,373)
Proceeds from maturities of marketable securities	17,757	3,000
Net cash used in investing activities	(13,463)	(38,243)
Cash flows from financing activities:
Proceeds from issuances of common stock	7,712	19,108
Purchase and retirement of common stock	0	(10,963)
Tax withholdings related to net share settlements of equity awards	(5,694)	(6,617)
Principal repayments on term loan	(33,750)	(24,375)
Net cash used in financing activities	(31,732)	(22,847)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(516)	2,481
Net increase in cash, cash equivalents and restricted cash	427	1,257
Cash, cash equivalents and restricted cash, beginning of period	92,726	102,596
Cash, cash equivalents and restricted cash, end of period	93,153	103,853
Non-cash investing and financing activities:
Change in accounts payable and accrued liabilities related to property, plant and equipment purchases	4,724	(283)
Supplemental disclosure of cash flow information:
Cash paid for income taxes, net	2,513	2,847
Cash paid for interest	$ 2,299	$ 2,974

Basis of Presentation and New A

Basis of Presentation and New Accounting Pronouncements	9 Months Ended
	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and New Accounting Pronouncements	Basis of Presentation and New Accounting Pronouncements Basis of Presentation The accompanying condensed consolidated financial information of FormFactor, Inc. is unaudited and has been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission. However, such information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. The financial information as of December 30, 2017 is derived from our 2017 Annual Report on Form 10-K. The condensed consolidated financial statements included herein should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2017 Annual Report on Form 10-K. The results of operations for the interim periods presented are not necessarily indicative of the results to be expected for the full year. Fiscal Year We operate on a 52 / 53 week fiscal year, whereby the fiscal year ends on the last Saturday of December. Fiscal 2018 and 2017 each contain 52 weeks and the nine months ended September 29, 2018 and September 30, 2017 each contained 39 weeks. Fiscal 2018 will end on December 29, 2018 . Reclassifications Certain immaterial reclassifications were made to the prior period financial statements to conform to the current period presentation. Critical Accounting Policies Except as described below, our critical accounting policies have not changed during the nine months ended September 29, 2018 from those disclosed in our Annual Report on Form 10-K for the year ended December 30, 2017 . 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 as our performance obligations are satisfied. This is typically the contractual service period, which ranges from one to two 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 standalone selling price. The stand-alone selling prices are determined based on the prices at which we separately sell these products. For items that are not sold separately, we estimate the stand-alone selling prices using our best estimate of selling price. Transaction price allocated to the remaining performance obligations: On September 29, 2018 , we had $3.5 million of remaining performance obligations, which were comprised of deferred service contracts and extended warranty contracts not yet delivered. We expect to recognize approximately 54.4% of our remaining performance obligations as revenue in fiscal 2019, and approximately 13.2% in fiscal 2020 and thereafter. The foregoing excludes the value of other remaining performance obligations as they 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 September 29, 2018 and December 30, 2017 were $1.4 million and $1.6 million , respectively, and are reported on the Condensed Consolidated Balance Sheet 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 Condensed 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 as of September 29, 2018 and December 30, 2017 were $5.4 million and $5.7 million . During the three and nine months ended September 29, 2018 , we recognized $0.2 million and $3.9 million of revenue, respectively, 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 12 of Notes to Consolidated Financial Statements for further details. New Accounting Pronouncements ASU 2016-10, ASU 2015-14 and ASU 2014-09 In May 2014, the Financial Accounting Standard Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, " Revenue from Contracts with Customers, " and, in August 2015, the FASB issued ASU 2015-14, “ Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, ” which defers the effective date of ASU 2014-09 by one year. 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. In April 2016, the FASB issued ASU 2016-10, “ Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing ” which was issued to clarify ASC Topic 606, “Revenue from Contracts with Customers” related to (i) identifying performance obligations; and (ii) the licensing implementation guidance. We adopted ASC 606, Revenue from Contracts with Customers and all related amendments (collectively “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. Additionally, we do not expect the adoption of the revenue standard to have a material impact to our net income on an ongoing basis. 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 the three or nine months ended September 29, 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. 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 September 30, 2017 December 31, 2016 Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows $ 91,184 $ 103,083 $ 101,408 Current assets - Restricted cash 372 4 106 Restricted cash 1,170 766 1,082 Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows $ 92,726 $ 103,853 $ 102,596 As of September 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 2016-02, 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 and 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 and lease liabilities.

Concentration of Credit and Oth

Concentration of Credit and Other Risks	9 Months Ended
	Sep. 29, 2018
Risks and Uncertainties [Abstract]
Concentration of Credit and Other Risks	Concentration of Credit and Other Risks Each of the following customers accounted for 10% or more of our revenues for the periods indicated: Three Months Ended Nine Months Ended September 29, 2018 September 30, 2017 September 29, 2018 September 30, 2017 Intel 24.5 % 30.6 % 18.0 % 27.4 % Micron 12.0 * 10.1 * SK Hynix * * 10.2 * Total revenues attributable to 10% or greater customers 36.5 % 30.6 % 38.3 % 27.4 % *Represents less than 10% of total revenues. At September 29, 2018 , two customers accounted for 25.4% and 10.2% of gross accounts receivable, respectively. At December 30, 2017 , two customers accounted for 24.1% and 13.6% of gross accounts receivable, respectively. No other customers accounted for 10% or more of gross accounts receivable at either of these fiscal period ends.

Inventories

Inventories	9 Months Ended
	Sep. 29, 2018
Inventory Disclosure [Abstract]
Inventories	Inventories, net 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. Inventories, net, consisted of the following (in thousands): September 29, December 30, Raw materials $ 44,793 $ 33,101 Work-in-progress 21,922 20,134 Finished goods 14,823 14,613 $ 81,538 $ 67,848

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 29, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill by reportable segment was as follows (in thousands): Probe Cards Systems Total 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 — (493 ) (493 ) Goodwill, gross, as of September 29, 2018 $ 172,482 $ 16,945 $ 189,427 We have not recorded any goodwill impairments as of September 29, 2018 . Intangible assets were as follows (in thousands): September 29, 2018 December 30, 2017 Other Intangible Assets Gross Accumulated Amortization Net Gross Accumulated Amortization Net Existing developed technologies $ 143,577 $ 92,074 $ 51,503 $ 143,966 $ 76,826 $ 67,140 Trade name 12,042 8,136 3,906 12,086 5,735 6,351 Customer relationships 40,196 20,327 19,869 40,313 16,320 23,993 Backlog — — — 15,811 15,811 — $ 195,815 $ 120,537 $ 75,278 $ 212,176 $ 114,692 $ 97,484 Amortization expense was included in our Condensed Consolidated Statements of Income as follows (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Cost of revenues $ 5,123 $ 5,473 $ 15,418 $ 17,411 Selling, general and administrative 2,389 2,043 6,458 6,098 $ 7,512 $ 7,516 $ 21,876 $ 23,509 The estimated future amortization of intangible assets is as follows (in thousands): Fiscal Year Amount Remainder of 2018 $ 7,509 2019 26,432 2020 23,421 2021 12,655 2022 3,215 Thereafter 2,046 $ 75,278

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 29, 2018
Payables and Accruals [Abstract]
Accrued Liabilities	Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 29, 2018 December 30, 2017 Accrued compensation and benefits $ 14,002 $ 18,141 Accrued warranty 2,457 3,662 Accrued withholding for employee stock purchase plan 1,430 3,279 Accrued income and other taxes 3,397 3,965 Other accrued expenses 3,591 4,647 $ 24,877 $ 33,694

Fair Value and Derivative Instr

Fair Value and Derivative Instruments	9 Months Ended
	Sep. 29, 2018
Fair Value Disclosures [Abstract]
Fair Value and Derivative Instruments	Fair Value and Derivative Instruments 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 the nine months ended September 29, 2018 or the year ended December 30, 2017 . 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 the first nine months of fiscal 2018 . Assets and Liabilities Measured at Fair Value on a Recurring Basis Assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): September 29, 2018 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 265 $ — $ 265 Commercial paper — 999 999 Total cash equivalents 265 999 1,264 Marketable securities: U.S. Treasuries 4,453 — 4,453 Certificates of deposit — 1,197 1,197 Agency securities — 8,994 8,994 Corporate bonds — 32,186 32,186 Commercial paper — 3,279 3,279 Total marketable securities 4,453 45,656 50,109 Interest rate swap derivative contracts — 951 951 Total assets $ 4,718 $ 47,606 $ 52,324 December 30, 2017 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 1,064 $ — $ 1,064 Corporate bonds — 774 774 Total cash equivalents 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 Total marketable securities 3,963 45,025 48,988 Foreign exchange derivative contracts — 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 September 29, 2018 or December 30, 2017 . 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. Unrealized gains and losses were immaterial and were recorded as a component of Accumulated other comprehensive income in our Condensed Consolidated Balance Sheets. We did not have any other-than-temporary unrealized gains or losses at either period end included in these financial statements. Interest Rate Swaps The fair value of our interest rate swap contracts is determined at the end of each reporting period based on valuation models that use interest rate yield curves as inputs. For accounting purposes, our interest rate swap contracts qualify for, and are designated as, cash flow hedges. The cash flows associated with the interest rate swaps are reported in Net cash provided by operating activities in our Condensed Consolidated Statements of Cash Flows and the fair value of the interest rate swap contracts are recorded within Prepaid expenses and other current assets and Other assets in our Condensed Consolidated Balance Sheets. The impact of the interest rate swaps on our Condensed Consolidated Statements of Income was as follows (in thousands): Amount of Gain or (Loss) Recognized in OCI on Derivative Location of Gain or (Loss) Reclassified from Accumulated OCI into Income Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income Location of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion) Three Months Ended September 29, 2018 $ 62 Interest expense $ 196 Interest expense Three Months Ended September 30, 2017 $ 18 Interest expense $ 54 Interest expense Nine Months Ended September 29, 2018 $ 418 Interest expense $ 514 Interest expense Nine Months Ended September 30, 2017 $ 8 Interest expense $ (32 ) Interest expense Foreign Exchange Derivative Contracts We operate and sell our products in various global markets. As a result, we are exposed to changes in foreign currency exchange rates. We utilize foreign currency forward contracts to hedge against future movements in foreign exchange rates that affect certain existing foreign currency denominated assets and liabilities and forecasted foreign currency revenue and expense transactions. Under this program, our strategy is to have increases or decreases in our foreign currency exposures mitigated by gains or losses on the foreign currency forward contracts in order to mitigate the risks and volatility associated with foreign currency transaction gains or losses. We do not use derivative financial instruments for speculative or trading purposes. For accounting purposes, our foreign currency forward contracts are not designated as hedging instruments and, accordingly, we record the fair value of these contracts as of the end of our reporting period in our Condensed Consolidated Balance Sheets with changes in fair value recorded within Other income (expense), net in our Condensed Consolidated Statement of Income for both realized and unrealized gains and losses. The fair value of our foreign exchange derivative contracts was determined based on current foreign currency exchange rates and forward points. All of our foreign exchange derivative contracts outstanding at September 29, 2018 will mature in the third quarter of fiscal 2018. The following table provides information about our foreign currency forward contracts outstanding as of September 29, 2018 (in thousands): Currency Contract Position Contract Amount (Local Currency) Contract Amount (U.S. Dollars) Japanese Yen Sell (2,241,544 ) $ 19,783 Taiwan Dollar Buy 49,404 (1,626 ) Korean Won Buy 4,508,988 (4,082 ) Euro Dollar Sell (15,050 ) 17,574 Total USD notional amount of outstanding foreign exchange contracts $ 31,649 Our foreign currency contracts are classified within Level 2 of the fair value hierarchy as they are valued using pricing models that utilize observable market inputs. The location and amount of net income (loss) related to non-designated derivative instruments in the Condensed Consolidated Statements of Income were as follows (in thousands): Three Months Ended Nine Months Ended Derivatives Not Designated as Hedging Instruments Location of Loss Recognized on Derivatives September 29, 2018 September 30, 2017 September 29, 2018 September 30, 2017 Foreign exchange forward contracts Other income (expense), net $ 706 $ (556 ) $ 923 $ (2,364 ) 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. There were no assets or liabilities measured at fair value on a nonrecurring basis during the three or nine months ended September 29, 2018 or September 30, 2017 .

Restructuring Charges

Restructuring Charges	9 Months Ended
	Sep. 29, 2018
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges Restructuring charges are comprised of costs related to employee termination benefits as well as contract termination costs, and are included in Restructuring in the Consolidated Statements of Income. Restructuring charges in the first three quarters of fiscal 2017 related to the consolidation of an acquired subsidiary into our operations. There were no restructuring charges in the first three quarters of fiscal 2018. Changes to the restructuring accrual in the nine months ended September 29, 2018 were as follows (in thousands): Accrual December 30, 2017 $ 399 Cash payments (399 ) September 29, 2018 $ —

Warranty

Warranty	9 Months Ended
	Sep. 29, 2018
Product Warranties Disclosures [Abstract]
Warranty	Warranty 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 as a component of Cost of revenues in our Condensed Consolidated Statement of Income. Changes in our warranty liability were as follows (in thousands): Nine Months Ended September 29, September 30, Balance at beginning of period $ 3,662 $ 2,972 Accruals 3,168 4,888 Settlements (4,373 ) (5,009 ) Balance at end of period $ 2,457 $ 2,851

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 29, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity and Stock-Based Compensation Common Stock Repurchase 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 employee stock purchase plan and equity incentive plan. The share repurchase program will expire on February 1, 2020. Repurchased shares are retired upon the settlement of the related transactions with the excess of cost over par value charged to additional paid-in capital. All repurchases are made in compliance with Rule 10b-18 under the Securities Exchange Act of 1934, as amended. During the nine months ended September 29, 2018 , we did not repurchase any shares. As of September 29, 2018 , $6.0 million remained available for future repurchases. Restricted Stock Units Restricted stock unit ("RSU") activity under our equity incentive plan was as follows: Units Weighted Average Grant Date Fair Value RSUs at December 30, 2017 3,148,061 $ 11.22 Awards granted 1,551,770 13.79 Awards vested (1,271,132 ) 10.45 Awards forfeited (293,969 ) 11.60 RSUs at September 29, 2018 3,134,730 $ 12.77 The total fair value of RSUs vested during the nine months ended September 29, 2018 was $17.3 million . Performance Restricted Stock Units We may grant Performance RSUs ("PRSUs") to certain executives, which vest based upon us achieving certain market performance criteria. On August 16, 2018, we granted a total of 318,100 PRSUs to nine senior executives for a total grant date fair value of $4.7 million , which will be recognized ratably over the requisite service period. The performance criteria are based on a metric called Total Shareholder Return ("TSR") for the period from July 1, 2018 to June 30, 2021, relative to the TSR of the companies identified as being part of the S&P Semiconductor Select Industry Index (FormFactor peer companies) as of June 30, 2018. There were no other PRSUs granted during the nine months ended September 29, 2018 . Stock Options Stock option activity under our equity incentive plan was as follows: Options Outstanding 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 (105,610 ) 9.93 Outstanding at September 29, 2018 553,724 $ 7.77 3.56 $ 3,308,931 Exercisable at September 29, 2018 430,104 $ 7.67 3.54 $ 2,620,928 Employee Stock Purchase Plan Information related to activity under our Employee Stock Purchase Plan ("ESPP") was as follows: Nine Months Ended September 29, 2018 Shares issued 610,297 Weighted average per share purchase price $ 12.84 Weighted average per share discount from the fair value of our common stock on the date of issuance $ 2.82 Stock-Based Compensation Stock-based compensation was included in our Condensed Consolidated Statements of Income as follows (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Cost of revenues $ 832 $ 894 $ 2,565 $ 2,540 Research and development 1,312 1,437 3,870 3,768 Selling, general and administrative 2,393 2,255 5,986 4,971 Total stock-based compensation $ 4,537 $ 4,586 $ 12,421 $ 11,279 Unrecognized Compensation Costs At September 29, 2018 , the unrecognized stock-based compensation was as follows (in thousands): Unrecognized Expense Average Expected Recognition Period in Years Stock options $ 167 0.36 Restricted stock units 28,035 2.76 Performance restricted stock units 6,580 2.38 Employee stock purchase plan 974 0.34 Total unrecognized stock-based compensation expense $ 35,756 1.76

Net Income (Loss) per Share

Net Income (Loss) per Share	9 Months Ended
	Sep. 29, 2018
Earnings Per Share [Abstract]
Net Income (Loss) per Share	Net Income per Share The following table reconciles the shares used in calculating basic net income per share and diluted net income per share (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Weighted-average shares used in computing basic net income per share 73,837 72,651 73,273 72,103 Add potentially dilutive securities 1,125 1,234 1,355 1,437 Weighted-average shares used in computing diluted net income per share 74,962 73,885 74,628 73,540 Securities not included as they would have been antidilutive 5 — 21 77

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 29, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Contractual Commitments and Purchase Obligations During the second quarter of 2018, we amended our lease for our Beaverton, Oregon facility, which extended the lease through 2027. During the third quarter of 2018, we amended our lease for our Livermore, California facility, which extended the lease through 2028. Our purchase obligations and other contractual obligations have not materially changed as of September 29, 2018 from those disclosed in our Annual Report on Form 10-K for the year ended December 30, 2017 . Future minimum payments under our non-cancelable operating leases were as follows as of September 29, 2018 (in thousands): Fiscal Year Amount Remainder of 2018 $ 1,698 2019 5,944 2020 5,861 2021 5,663 2022 4,784 Thereafter 24,737 Total $ 48,687 Legal Matters From time to time, we may be subject to legal proceedings and claims in the ordinary course of business. As of September 29, 2018 , and as of the filing of this Quarterly Report on Form 10-Q, we were not involved in any material legal proceedings.

Operating Segments

Operating Segments	9 Months Ended
	Sep. 29, 2018
Segment Reporting [Abstract]
Operating Segments	Operating Segments and Enterprise-Wide Information 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. We operate in two reportable segments consisting of the Probe Cards segment and the Systems segment. The following table summarizes the operating results by reportable segment (dollars in thousands): Three Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Corporate and Other Total Probe Cards Systems Corporate and Other Total Revenues $ 111,606 $ 23,383 $ — $ 134,989 $ 119,439 $ 24,296 $ — $ 143,735 Gross profit $ 47,675 $ 11,250 $ (5,955 ) $ 52,970 $ 51,438 $ 12,571 $ (6,379 ) $ 57,630 Gross margin 42.7 % 48.1 % — % 39.2 % 43.1 % 51.7 % — % 40.1 % Operating income (loss) $ 25,609 $ 4,228 $ (20,469 ) $ 9,368 $ 17,894 $ 5,277 $ (8,905 ) $ 14,266 Nine Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Corporate and Other Total Probe Cards Systems Corporate and Other Total Revenues $ 318,120 $ 70,668 $ — $ 388,788 $ 347,559 $ 68,981 $ — $ 416,540 Gross profit $ 138,182 $ 34,118 $ (17,983 ) $ 154,317 $ 151,204 $ 36,176 $ (20,412 ) $ 166,968 Gross margin 43.4 % 48.3 % — % 39.7 % 43.5 % 52.4 % — % 40.1 % Operating income (loss) $ 71,326 $ 12,634 $ (59,647 ) $ 24,313 $ 54,289 $ 14,363 $ (27,748 ) $ 40,904 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 general and administrative costs, amortization of intangible assets, share-based compensation, 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. Certain revenue category information by reportable segment was as follows (in thousands): Three Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Total Probe Cards Systems Total Market: Foundry & Logic $ 61,270 $ — $ 61,270 $ 81,914 $ — $ 81,914 DRAM 37,359 — 37,359 32,373 — 32,373 Flash 12,977 — 12,977 5,151 — 5,151 Systems — 23,383 23,383 — 24,297 24,297 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Timing of revenue recognition: Products transferred at a point in time $ 111,020 $ 22,422 $ 133,442 $ 118,995 $ 23,372 $ 142,367 Services transferred over time 586 961 1,547 443 925 1,368 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Geographical region: United States $ 34,398 $ 5,729 $ 40,127 $ 48,544 $ 8,712 $ 57,256 Taiwan 18,904 777 19,681 15,951 1,863 17,814 South Korea 19,664 1,437 21,101 21,217 545 21,762 Asia-Pacific 1 22,388 6,825 29,213 19,136 4,664 23,800 Europe 5,499 3,629 9,128 6,015 6,079 12,094 Japan 10,462 4,273 14,735 8,419 2,037 10,456 Rest of the world 291 713 1,004 156 397 553 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Nine Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Total Probe Cards Systems Total Market: Foundry & Logic $ 181,819 $ — $ 181,819 $ 244,952 $ — $ 244,952 DRAM 105,716 — 105,716 92,798 — 92,798 Flash 30,585 — 30,585 9,809 — 9,809 Systems — 70,668 70,668 — 68,981 68,981 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 Timing of revenue recognition: Products transferred at a point in time $ 316,495 $ 67,794 $ 384,289 $ 346,191 $ 66,388 $ 412,579 Services transferred over time 1,625 2,874 4,499 1,368 2,593 3,961 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 Geographical region: United States $ 89,960 $ 16,861 $ 106,821 $ 126,110 $ 21,384 $ 147,494 Taiwan 71,300 5,680 76,980 61,568 5,593 67,161 South Korea 58,250 4,317 62,567 60,306 2,909 63,215 Asia-Pacific 1 50,956 16,263 67,219 53,620 16,606 70,226 Europe 15,181 14,969 30,150 17,664 13,808 31,472 Japan 31,426 10,523 41,949 27,219 7,847 35,066 Rest of the world 1,047 2,055 3,102 1,072 834 1,906 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 1 Asia-Pacific includes all countries in the region except Taiwan, South Korea, and Japan, which are disclosed separately .

Basis of Presentation and New_2

Basis of Presentation and New Accounting Pronouncements (Policies)	9 Months Ended
	Sep. 29, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying condensed consolidated financial information of FormFactor, Inc. is unaudited and has been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and pursuant to the rules and regulations of the Securities and Exchange Commission. However, such information reflects all adjustments, consisting only of normal recurring adjustments, which are, in the opinion of management, necessary for a fair presentation of the financial position, results of operations and cash flows for the interim periods. The financial information as of December 30, 2017 is derived from our 2017 Annual Report on Form 10-K. The condensed consolidated financial statements included herein should be read in conjunction with the consolidated financial statements and the notes thereto included in our 2017 Annual Report on Form 10-K. The results of operations for the interim periods presented are not necessarily indicative of the results to be expected for the full year.
Fiscal Year	Fiscal Year We operate on a 52 / 53 week fiscal year, whereby the fiscal year ends on the last Saturday of December. Fiscal 2018 and 2017 each contain 52 weeks and the nine months ended September 29, 2018 and September 30, 2017 each contained 39 weeks. Fiscal 2018 will end on December 29, 2018 .
Reclassifications	Reclassifications Certain immaterial reclassifications were made to the prior period financial statements to conform to the current period presentation.
Significant Accounting Policies [Text Block]	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 as our performance obligations are satisfied. This is typically the contractual service period, which ranges from one to two 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 standalone selling price. The stand-alone selling prices are determined based on the prices at which we separately sell these products. For items that are not sold separately, we estimate the stand-alone selling prices using our best estimate of selling price. Transaction price allocated to the remaining performance obligations: On September 29, 2018 , we had $3.5 million of remaining performance obligations, which were comprised of deferred service contracts and extended warranty contracts not yet delivered. We expect to recognize approximately 54.4% of our remaining performance obligations as revenue in fiscal 2019, and approximately 13.2% in fiscal 2020 and thereafter. The foregoing excludes the value of other remaining performance obligations as they 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 September 29, 2018 and December 30, 2017 were $1.4 million and $1.6 million , respectively, and are reported on the Condensed Consolidated Balance Sheet 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 Condensed 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 as of September 29, 2018 and December 30, 2017 were $5.4 million and $5.7 million . During the three and nine months ended September 29, 2018 , we recognized $0.2 million and $3.9 million of revenue, respectively, 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
New Accounting Pronouncements	New Accounting Pronouncements ASU 2016-10, ASU 2015-14 and ASU 2014-09 In May 2014, the Financial Accounting Standard Board ("FASB") issued Accounting Standards Update ("ASU") No. 2014-09, " Revenue from Contracts with Customers, " and, in August 2015, the FASB issued ASU 2015-14, “ Revenue from Contracts with Customers (Topic 606): Deferral of the Effective Date, ” which defers the effective date of ASU 2014-09 by one year. 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. In April 2016, the FASB issued ASU 2016-10, “ Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing ” which was issued to clarify ASC Topic 606, “Revenue from Contracts with Customers” related to (i) identifying performance obligations; and (ii) the licensing implementation guidance. We adopted ASC 606, Revenue from Contracts with Customers and all related amendments (collectively “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. Additionally, we do not expect the adoption of the revenue standard to have a material impact to our net income on an ongoing basis. 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 the three or nine months ended September 29, 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. 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 September 30, 2017 December 31, 2016 Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows $ 91,184 $ 103,083 $ 101,408 Current assets - Restricted cash 372 4 106 Restricted cash 1,170 766 1,082 Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows $ 92,726 $ 103,853 $ 102,596 As of September 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 2016-02, 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 and 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 and lease liabilities.
Fair Value Policy	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. 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 the nine months ended September 29, 2018 or the year ended December 30, 2017 . 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 the first nine months of fiscal 2018 .

Concentration of Credit and O_2

Concentration of Credit and Other Risks (Tables)	9 Months Ended
	Sep. 29, 2018
Risks and Uncertainties [Abstract]
Schedule of Customer Percentage of Revenue	Each of the following customers accounted for 10% or more of our revenues for the periods indicated: Three Months Ended Nine Months Ended September 29, 2018 September 30, 2017 September 29, 2018 September 30, 2017 Intel 24.5 % 30.6 % 18.0 % 27.4 % Micron 12.0 * 10.1 * SK Hynix * * 10.2 * Total revenues attributable to 10% or greater customers 36.5 % 30.6 % 38.3 % 27.4 %

Inventories (Tables)

Inventories (Tables)	9 Months Ended
	Sep. 29, 2018
Inventory Disclosure [Abstract]
Schedule of Inventory Components	Inventories, net, consisted of the following (in thousands): September 29, December 30, Raw materials $ 44,793 $ 33,101 Work-in-progress 21,922 20,134 Finished goods 14,823 14,613 $ 81,538 $ 67,848

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 29, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill by Reportable Segments	Goodwill by reportable segment was as follows (in thousands): Probe Cards Systems Total 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 — (493 ) (493 ) Goodwill, gross, as of September 29, 2018 $ 172,482 $ 16,945 $ 189,427
Schedule of Intangible Assets	Intangible assets were as follows (in thousands): September 29, 2018 December 30, 2017 Other Intangible Assets Gross Accumulated Amortization Net Gross Accumulated Amortization Net Existing developed technologies $ 143,577 $ 92,074 $ 51,503 $ 143,966 $ 76,826 $ 67,140 Trade name 12,042 8,136 3,906 12,086 5,735 6,351 Customer relationships 40,196 20,327 19,869 40,313 16,320 23,993 Backlog — — — 15,811 15,811 — $ 195,815 $ 120,537 $ 75,278 $ 212,176 $ 114,692 $ 97,484
Schedule of Amortization Expense	Amortization expense was included in our Condensed Consolidated Statements of Income as follows (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Cost of revenues $ 5,123 $ 5,473 $ 15,418 $ 17,411 Selling, general and administrative 2,389 2,043 6,458 6,098 $ 7,512 $ 7,516 $ 21,876 $ 23,509
Schedule of Estimated Amortization of Intangible Assets	The estimated future amortization of intangible assets is as follows (in thousands): Fiscal Year Amount Remainder of 2018 $ 7,509 2019 26,432 2020 23,421 2021 12,655 2022 3,215 Thereafter 2,046 $ 75,278

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 29, 2018
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities [Table Text Block]	Accrued liabilities consisted of the following (in thousands): September 29, 2018 December 30, 2017 Accrued compensation and benefits $ 14,002 $ 18,141 Accrued warranty 2,457 3,662 Accrued withholding for employee stock purchase plan 1,430 3,279 Accrued income and other taxes 3,397 3,965 Other accrued expenses 3,591 4,647 $ 24,877 $ 33,694

Fair Value and Derivative Ins_2

Fair Value and Derivative Instruments (Tables)	9 Months Ended
	Sep. 29, 2018
Fair Value Disclosures [Abstract]
Fair Value Assets Measured on Recurring Basis	Assets and liabilities measured at fair value on a recurring basis were as follows (in thousands): September 29, 2018 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 265 $ — $ 265 Commercial paper — 999 999 Total cash equivalents 265 999 1,264 Marketable securities: U.S. Treasuries 4,453 — 4,453 Certificates of deposit — 1,197 1,197 Agency securities — 8,994 8,994 Corporate bonds — 32,186 32,186 Commercial paper — 3,279 3,279 Total marketable securities 4,453 45,656 50,109 Interest rate swap derivative contracts — 951 951 Total assets $ 4,718 $ 47,606 $ 52,324 December 30, 2017 Level 1 Level 2 Total Assets: Cash equivalents: Money market funds $ 1,064 $ — $ 1,064 Corporate bonds — 774 774 Total cash equivalents 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 Total marketable securities 3,963 45,025 48,988 Foreign exchange derivative contracts — 31 31 Interest rate swap derivative contracts — 1,043 1,043 Total assets $ 5,027 $ 46,873 $ 51,900
Schedule of the Impact of Cash Flow Hedges on Consolidated Financial Statements	The impact of the interest rate swaps on our Condensed Consolidated Statements of Income was as follows (in thousands): Amount of Gain or (Loss) Recognized in OCI on Derivative Location of Gain or (Loss) Reclassified from Accumulated OCI into Income Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income Location of Gain or (Loss) Recognized in Income on Derivative (Ineffective Portion) Three Months Ended September 29, 2018 $ 62 Interest expense $ 196 Interest expense Three Months Ended September 30, 2017 $ 18 Interest expense $ 54 Interest expense Nine Months Ended September 29, 2018 $ 418 Interest expense $ 514 Interest expense Nine Months Ended September 30, 2017 $ 8 Interest expense $ (32 ) Interest expense
Schedule of Foreign Currency Forward Contracts	The following table provides information about our foreign currency forward contracts outstanding as of September 29, 2018 (in thousands): Currency Contract Position Contract Amount (Local Currency) Contract Amount (U.S. Dollars) Japanese Yen Sell (2,241,544 ) $ 19,783 Taiwan Dollar Buy 49,404 (1,626 ) Korean Won Buy 4,508,988 (4,082 ) Euro Dollar Sell (15,050 ) 17,574 Total USD notional amount of outstanding foreign exchange contracts $ 31,649
Schedule of Gains and Losses Related to Non-designated Derivative Instruments	Three Months Ended Nine Months Ended Derivatives Not Designated as Hedging Instruments Location of Loss Recognized on Derivatives September 29, 2018 September 30, 2017 September 29, 2018 September 30, 2017 Foreign exchange forward contracts Other income (expense), net $ 706 $ (556 ) $ 923 $ (2,364 )

Restructuring Charges (Tables)

Restructuring Charges (Tables)	9 Months Ended
	Sep. 29, 2018
Restructuring and Related Activities [Abstract]
Schedule of Restructuring Accrual Activity	Changes to the restructuring accrual in the nine months ended September 29, 2018 were as follows (in thousands): Accrual December 30, 2017 $ 399 Cash payments (399 ) September 29, 2018 $ —

Warranty (Tables)

Warranty (Tables)	9 Months Ended
	Sep. 29, 2018
Product Warranties Disclosures [Abstract]
Reconciliation of Changes in Warranty Liability	Changes in our warranty liability were as follows (in thousands): Nine Months Ended September 29, September 30, Balance at beginning of period $ 3,662 $ 2,972 Accruals 3,168 4,888 Settlements (4,373 ) (5,009 ) Balance at end of period $ 2,457 $ 2,851

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 29, 2018
Equity [Abstract]
Schedule of Restricted Stock Unit Activity	Restricted stock unit ("RSU") activity under our equity incentive plan was as follows: Units Weighted Average Grant Date Fair Value RSUs at December 30, 2017 3,148,061 $ 11.22 Awards granted 1,551,770 13.79 Awards vested (1,271,132 ) 10.45 Awards forfeited (293,969 ) 11.60 RSUs at September 29, 2018 3,134,730 $ 12.77
Schedule of Stock Option Activity	Stock option activity under our equity incentive plan was as follows: Options Outstanding 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 (105,610 ) 9.93 Outstanding at September 29, 2018 553,724 $ 7.77 3.56 $ 3,308,931 Exercisable at September 29, 2018 430,104 $ 7.67 3.54 $ 2,620,928
Schedule of ESPP Activity	Information related to activity under our Employee Stock Purchase Plan ("ESPP") was as follows: Nine Months Ended September 29, 2018 Shares issued 610,297 Weighted average per share purchase price $ 12.84 Weighted average per share discount from the fair value of our common stock on the date of issuance $ 2.82
Schedule of Stock-based Compensation	Stock-based compensation was included in our Condensed Consolidated Statements of Income as follows (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Cost of revenues $ 832 $ 894 $ 2,565 $ 2,540 Research and development 1,312 1,437 3,870 3,768 Selling, general and administrative 2,393 2,255 5,986 4,971 Total stock-based compensation $ 4,537 $ 4,586 $ 12,421 $ 11,279
Schedule of Unrecognized Stock-based Compensation	At September 29, 2018 , the unrecognized stock-based compensation was as follows (in thousands): Unrecognized Expense Average Expected Recognition Period in Years Stock options $ 167 0.36 Restricted stock units 28,035 2.76 Performance restricted stock units 6,580 2.38 Employee stock purchase plan 974 0.34 Total unrecognized stock-based compensation expense $ 35,756 1.76

Net Income (Loss) per Share (Ta

Net Income (Loss) per Share (Tables)	9 Months Ended
	Sep. 29, 2018
Earnings Per Share [Abstract]
Schedule of Calculation of Numerator and Denominator in Earnings Per Share	The following table reconciles the shares used in calculating basic net income per share and diluted net income per share (in thousands): Three Months Ended Nine Months Ended September 29, September 30, September 29, September 30, Weighted-average shares used in computing basic net income per share 73,837 72,651 73,273 72,103 Add potentially dilutive securities 1,125 1,234 1,355 1,437 Weighted-average shares used in computing diluted net income per share 74,962 73,885 74,628 73,540 Securities not included as they would have been antidilutive 5 — 21 77

Operating Segments (Tables)

Operating Segments (Tables)	9 Months Ended
	Sep. 29, 2018
Segment Reporting [Abstract]
Schedule of Operating Results by Segment	The following table summarizes the operating results by reportable segment (dollars in thousands): Three Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Corporate and Other Total Probe Cards Systems Corporate and Other Total Revenues $ 111,606 $ 23,383 $ — $ 134,989 $ 119,439 $ 24,296 $ — $ 143,735 Gross profit $ 47,675 $ 11,250 $ (5,955 ) $ 52,970 $ 51,438 $ 12,571 $ (6,379 ) $ 57,630 Gross margin 42.7 % 48.1 % — % 39.2 % 43.1 % 51.7 % — % 40.1 % Operating income (loss) $ 25,609 $ 4,228 $ (20,469 ) $ 9,368 $ 17,894 $ 5,277 $ (8,905 ) $ 14,266 Nine Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Corporate and Other Total Probe Cards Systems Corporate and Other Total Revenues $ 318,120 $ 70,668 $ — $ 388,788 $ 347,559 $ 68,981 $ — $ 416,540 Gross profit $ 138,182 $ 34,118 $ (17,983 ) $ 154,317 $ 151,204 $ 36,176 $ (20,412 ) $ 166,968 Gross margin 43.4 % 48.3 % — % 39.7 % 43.5 % 52.4 % — % 40.1 % Operating income (loss) $ 71,326 $ 12,634 $ (59,647 ) $ 24,313 $ 54,289 $ 14,363 $ (27,748 ) $ 40,904
Disaggregation of Revenue by Segment	Certain revenue category information by reportable segment was as follows (in thousands): Three Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Total Probe Cards Systems Total Market: Foundry & Logic $ 61,270 $ — $ 61,270 $ 81,914 $ — $ 81,914 DRAM 37,359 — 37,359 32,373 — 32,373 Flash 12,977 — 12,977 5,151 — 5,151 Systems — 23,383 23,383 — 24,297 24,297 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Timing of revenue recognition: Products transferred at a point in time $ 111,020 $ 22,422 $ 133,442 $ 118,995 $ 23,372 $ 142,367 Services transferred over time 586 961 1,547 443 925 1,368 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Geographical region: United States $ 34,398 $ 5,729 $ 40,127 $ 48,544 $ 8,712 $ 57,256 Taiwan 18,904 777 19,681 15,951 1,863 17,814 South Korea 19,664 1,437 21,101 21,217 545 21,762 Asia-Pacific 1 22,388 6,825 29,213 19,136 4,664 23,800 Europe 5,499 3,629 9,128 6,015 6,079 12,094 Japan 10,462 4,273 14,735 8,419 2,037 10,456 Rest of the world 291 713 1,004 156 397 553 Total $ 111,606 $ 23,383 $ 134,989 $ 119,438 $ 24,297 $ 143,735 Nine Months Ended September 29, 2018 September 30, 2017 Probe Cards Systems Total Probe Cards Systems Total Market: Foundry & Logic $ 181,819 $ — $ 181,819 $ 244,952 $ — $ 244,952 DRAM 105,716 — 105,716 92,798 — 92,798 Flash 30,585 — 30,585 9,809 — 9,809 Systems — 70,668 70,668 — 68,981 68,981 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 Timing of revenue recognition: Products transferred at a point in time $ 316,495 $ 67,794 $ 384,289 $ 346,191 $ 66,388 $ 412,579 Services transferred over time 1,625 2,874 4,499 1,368 2,593 3,961 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 Geographical region: United States $ 89,960 $ 16,861 $ 106,821 $ 126,110 $ 21,384 $ 147,494 Taiwan 71,300 5,680 76,980 61,568 5,593 67,161 South Korea 58,250 4,317 62,567 60,306 2,909 63,215 Asia-Pacific 1 50,956 16,263 67,219 53,620 16,606 70,226 Europe 15,181 14,969 30,150 17,664 13,808 31,472 Japan 31,426 10,523 41,949 27,219 7,847 35,066 Rest of the world 1,047 2,055 3,102 1,072 834 1,906 Total $ 318,120 $ 70,668 $ 388,788 $ 347,559 $ 68,981 $ 416,540 1 Asia-Pacific includes all countries in the region except Taiwan, South Korea, and Japan, which are disclosed separately .

Basis of Presentation and New_3

Basis of Presentation and New Accounting Pronouncements - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 29, 2018	Sep. 29, 2018	Dec. 26, 2020	Dec. 28, 2019	Dec. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Performance obligations	$ 3.5	$ 3.5
Contract assets	1.4	1.4			$ 1.6
Contract liabilities	5.4	5.4			$ 5.7
Revenue recognized included in contracts	$ 0.2	$ 3.9
Forecast
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Expected to be recognized			13.20%	54.40%

Basis of Presentation and New_4

Basis of Presentation and New Accounting Pronouncements - ASU 2016-18 Information (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents as previously reported in the Condensed Consolidated Statements of Cash Flows	$ 91,990	$ 91,184	$ 103,083	$ 101,408
Current assets - Restricted cash	129	372	4	106
Restricted cash	1,034	1,170	766	1,082
Cash, cash equivalents and restricted cash as currently reported in the Condensed Consolidated Statements of Cash Flows	$ 93,153	$ 92,726	$ 103,853	$ 102,596

Concentration of Credit and O_3

Concentration of Credit and Other Risks (Details) - Customer Concentration Risk	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017
Revenues
Concentration Risk [Line Items]
Concentration risk percentage	36.50%	30.60%	38.30%	27.40%
Revenues | Intel
Concentration Risk [Line Items]
Concentration risk percentage	24.50%	30.60%	18.00%	27.40%
Revenues | Micron
Concentration Risk [Line Items]
Concentration risk percentage	12.00%		10.10%
Revenues | Micron
Concentration Risk [Line Items]
Concentration risk percentage			10.20%
Accounts Receivable | Major Customer 1
Concentration Risk [Line Items]
Concentration risk percentage			25.40%		24.10%
Accounts Receivable | Major Customer 2
Concentration Risk [Line Items]
Concentration risk percentage			10.20%		13.60%

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 44,793	$ 33,101
Work-in-progress	21,922	20,134
Finished goods	14,823	14,613
Inventories	$ 81,538	$ 67,848

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets - Goodwill (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 29, 2018	Dec. 30, 2017
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 189,920,000	$ 188,010,000
Foreign currency translation	(493,000)	1,910,000
Goodwill, ending balance	189,427,000	189,920,000
Goodwill impairment	0
Probe Cards
Goodwill [Roll Forward]
Goodwill, beginning balance	172,482,000	172,482,000
Foreign currency translation	0	0
Goodwill, ending balance	172,482,000	172,482,000
Systems
Goodwill [Roll Forward]
Goodwill, beginning balance	17,438,000	15,528,000
Foreign currency translation	(493,000)	1,910,000
Goodwill, ending balance	$ 16,945,000	$ 17,438,000

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	$ 195,815	$ 212,176
Accumulated Amortization	120,537	114,692
Intangible Assets, Net	75,278	97,484
Existing developed technologies
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	143,577	143,966
Accumulated Amortization	92,074	76,826
Intangible Assets, Net	51,503	67,140
Trade name
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	12,042	12,086
Accumulated Amortization	8,136	5,735
Intangible Assets, Net	3,906	6,351
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	40,196	40,313
Accumulated Amortization	20,327	16,320
Intangible Assets, Net	19,869	23,993
Backlog
Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Gross	0	15,811
Accumulated Amortization	0	15,811
Intangible Assets, Net	$ 0	$ 0

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets - Amortization Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 7,512	$ 7,516	$ 21,876	$ 23,509
Finite-Lived Intangible Assets, Net, Amortization Expense, Rolling Maturity [Abstract]
Remainder of 2018	7,509		7,509
2,019	26,432		26,432
2,020	23,421		23,421
2,021	12,655		12,655
2,022	3,215		3,215
Thereafter	2,046		2,046
Intangible Assets, Net	75,278		75,278		$ 97,484
Cost of revenues
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	5,123	5,473	15,418	17,411
Selling, general and administrative
Property, Plant and Equipment [Line Items]
Amortization of intangible assets	$ 2,389	$ 2,043	$ 6,458	$ 6,098

Accrued Liabilities (Details)

Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 29, 2018	Dec. 30, 2017
Payables and Accruals [Abstract]
Accrued compensation and benefits	$ 14,002	$ 18,141
Accrued warranty	2,457	3,662
Accrued withholding for employee stock purchase plan	1,430	3,279
Accrued income and other taxes	3,397	3,965
Other accrued expenses	3,591	4,647
Accrued liabilities	$ 24,877	$ 33,694

Fair Value and Derivative Ins_3

Fair Value and Derivative Instruments - Fair Value Assets Measured on Recurring Basis (Details) - USD ($)	Sep. 29, 2018	Dec. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 1,264,000	$ 1,838,000
Marketable securities	50,109,000	48,988,000
Total assets measured at fair value	52,324,000	51,900,000
Liabilities measured at fair value on recurring basis		0
Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	951,000	1,043,000
Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		31,000
Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	265,000	1,064,000
Corporate Bond Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		774,000
Marketable securities		30,636,000
US Treasury Bill Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	4,453,000	3,963,000
Certificates of deposit
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	1,197,000	957,000
Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	8,994,000	10,432,000
Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	32,186,000
Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	999,000
Marketable securities	3,279,000	3,000,000
Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	265,000	1,064,000
Marketable securities	4,453,000	3,963,000
Total assets measured at fair value	4,718,000	5,027,000
Level 1 | Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	0	0
Level 1 | Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		0
Level 1 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	265,000	1,064,000
Level 1 | Corporate Bond Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		0
Marketable securities		0
Level 1 | US Treasury Bill Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	4,453,000	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]
Marketable securities	0
Level 1 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0
Marketable securities	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	999,000	774,000
Marketable securities	45,656,000	45,025,000
Total assets measured at fair value	47,606,000	46,873,000
Level 2 | Money market funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	0	0
Level 2 | Corporate Bond Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents		774,000
Marketable securities		30,636,000
Level 2 | US Treasury Bill Securities [Member]
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	1,197,000	957,000
Level 2 | Agency securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	8,994,000	10,432,000
Level 2 | Corporate bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Marketable securities	32,186,000
Level 2 | Commercial paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	999,000
Marketable securities	3,279,000	3,000,000
Designated as Hedging Instrument | Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts	$ 951,000
Designated as Hedging Instrument | Level 2 | Interest rate swap derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		1,043,000
Designated as Hedging Instrument | Level 2 | Foreign exchange derivative contracts
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative contracts		$ 31,000

Restructuring Charges (Details)

Restructuring Charges (Details) $ in Thousands	9 Months Ended
	Sep. 29, 2018USD ($)
Restructuring Reserve [Roll Forward]
Accrual at beginning of period	$ 399
Cash payments	(399)
Accrual at end of period	$ 0

Fair Value and Derivative Ins_4

Fair Value and Derivative Instruments - Impact of Cash Flow Hedges and Derivatives (Details) - Interest Rate Contracts - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017	Dec. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	$ 951		$ 951		$ 1,043
Designated as Hedging Instrument
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative asset	951		951
Designated as Hedging Instrument | Cash Flow Hedging
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of Gain or (Loss) Recognized in OCI on Derivative (Effective Portion)	62	$ 18	418	$ 8
Designated as Hedging Instrument | Cash Flow Hedging | Other Income (Expense), Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of Gain or (Loss) Reclassified from Accumulated OCI into Income (Effective Portion)	$ 196	$ 54	$ 514	$ (32)

Fair Value and Derivative Ins_5

Fair Value and Derivative Instruments - Foreign Currency Forward Contracts (Details) - Sep. 29, 2018 - Foreign exchange forward contracts € in Thousands, ₩ in Thousands, ¥ in Thousands, $ in Thousands, $ in Thousands	USD ($)	KRW (₩)	TWD ($)	EUR (€)	JPY (¥)
Derivative [Line Items]
Contract amount (in various currencies)	$ 31,649
Sell | Japanese Yen
Derivative [Line Items]
Contract amount (in various currencies)	19,783				¥ (2,241,544)
Sell | Euro Dollar
Derivative [Line Items]
Contract amount (in various currencies)	17,574			€ (15,050)
Buy | Taiwan Dollar
Derivative [Line Items]
Contract amount (in various currencies)	(1,626)		$ 49,404
Buy | Korean Won
Derivative [Line Items]
Contract amount (in various currencies)	$ (4,082)	₩ 4,508,988

Fair Value and Derivative Ins_6

Fair Value and Derivative Instruments - Gains and Losses Related to Non-designated Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Derivatives Not Designated as Hedging Instruments | Foreign exchange forward contracts | Other income (expense), net
Derivatives, Fair Value [Line Items]
Foreign exchange forward contracts	$ 706	$ (556)	$ 923	$ (2,364)

Fair Value and Derivative Ins_7

Fair Value and Derivative Instruments - Assets Measured at Fair Value on a Non-Recurring Basis (Details) - USD ($)	Sep. 29, 2018	Dec. 30, 2017	Sep. 30, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on recurring basis		$ 0
Assets measured at fair value on non-recurring basis	$ 52,324,000	$ 51,900,000
Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on non-recurring basis	$ 0		$ 0

Warranty (Details)

Warranty (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017
Movement in Standard and Extended Product Warranty, Increase (Decrease) [Roll Forward]
Balance at beginning of period	$ 3,662	$ 2,972
Accruals	3,168	4,888
Settlements	(4,373)	(5,009)
Balance at end of period	$ 2,457	$ 2,851

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) - USD ($)	Aug. 16, 2018	Sep. 29, 2018	Feb. 28, 2017
Equity Incentive Plan | Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total fair value of restricted stock units vested during the period		$ 17,300,000
Awards granted (in shares)		1,551,770
Awards granted (in dollars per share)		$ 13.79
Equity Incentive Plan | PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted (in shares)	318,100
Awards granted (in dollars per share)	$ 4,700,000
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program authorized amount			$ 25,000,000
Amount remaining for future repurchases		$ 6,000,000

Stockholders' Equity - Restrict

Stockholders' Equity - Restricted Stock Unit Activity (Details) - Equity Incentive Plan - Restricted Stock Units	9 Months Ended
	Sep. 29, 2018$ / sharesshares
Units
Beginning balance (in shares) | shares	3,148,061
Awards granted (in shares) | shares	1,551,770
Awards vested (in shares) | shares	(1,271,132)
Awards canceled (in shares) | shares	(293,969)
Ending balance (in shares) | shares	3,134,730
Weighted Average Grant Date Fair Value
Beginning Balance (in dollars per share) | $ / shares	$ 11.22
Awards granted (in dollars per share) | $ / shares	13.79
Awards vested (in dollars per share) | $ / shares	10.45
Awards canceled (in dollars per share) | $ / shares	11.60
Ending Balance (in dollars per share) | $ / shares	$ 12.77

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Option Activity (Details) - Equity Incentive Plan $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 29, 2018USD ($)$ / sharesshares
Options Outstanding
Outstanding, beginning of period (In shares) | shares	659,334
Options exercised (In shares) | shares	(105,610)
Outstanding, end of period (In shares) | shares	553,724
Exercisable (In shares) | shares	430,104
Weighted Average Exercise Price
Outstanding, beginning of period (In dollars per share) | $ / shares	$ 8.12
Options exercised (In dollars per share) | $ / shares	9.93
Outstanding, end of period (In dollars per share) | $ / shares	7.77
Exercisable (In dollars per share) | $ / shares	$ 7.67
Additional Disclosures
Outstanding, weighted average remaining contractual life	3 years 6 months 22 days
Exercisable, weighted average remaining contractual life	3 years 6 months 16 days
Outstanding, aggregate intrinsic value | $	$ 3,308,931
Exercisable, aggregate intrinsic value | $	$ 2,620,928

Stockholders' Equity - ESPP Act

Stockholders' Equity - ESPP Activity (Details) - Employee stock purchase plan	9 Months Ended
	Sep. 29, 2018$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued under ESPP (In shares) | shares	610,297
Weighted average per share purchase price (in dollars per share)	$ 12.84
Weighted average per share discount from the fair value of our common stock on the date of issuance (in dollars per share)	$ 2.82

Stockholders' Equity - Stock-Ba

Stockholders' Equity - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 4,537	$ 4,586	$ 12,421	$ 11,279
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	832	894	2,565	2,540
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	1,312	1,437	3,870	3,768
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation	$ 2,393	$ 2,255	$ 5,986	$ 4,971

Stockholders' Equity - Unrecogn

Stockholders' Equity - Unrecognized Compensation Costs (Details) $ in Thousands	9 Months Ended
	Sep. 29, 2018USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized stock-based compensation expense	$ 35,756
Average expected recognition period	1 year 9 months 4 days
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, stock options	$ 167
Average expected recognition period	4 months 9 days
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, other than options	$ 28,035
Average expected recognition period	2 years 9 months 5 days
Performance restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, other than options	$ 6,580
Average expected recognition period	2 years 4 months 18 days
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized expense, other than options	$ 974
Average expected recognition period	4 months 2 days

Net Income (Loss) per Share (De

Net Income (Loss) per Share (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Weighted-average shares used in computing basic net income (loss) per share (In shares)	73,837	72,651	73,273	72,103
Add potentially dilutive securities (In shares)	1,125	1,234	1,355	1,437
Weighted-average shares used in computing diluted net income per share (In shares)	74,962	73,885	74,628	73,540
Anti-dilutive securities (In shares)	5	0	21	77

Commitments and Contingencies (

Commitments and Contingencies (Details) $ in Thousands	Sep. 29, 2018USD ($)
Commitments and Contingencies Disclosure [Abstract]
Remainder of 2018	$ 1,698
2,019	5,944
2,020	5,861
2,021	5,663
2,022	4,784
Thereafter	24,737
Total	$ 48,687

Operating Segments - Additional

Operating Segments - Additional Information (Details)	9 Months Ended
	Sep. 29, 2018segment
Segment Reporting [Abstract]
Number of reportable segments	2

Operating Segments - Operating

Operating Segments - Operating Results by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 134,989	$ 143,735	$ 388,788	$ 416,540
Gross profit	$ 52,970	$ 57,630	$ 154,317	$ 166,968
Gross margin	39.20%	40.10%	39.70%	40.10%
Operating income (loss)	$ 9,368	$ 14,266	$ 24,313	$ 40,904
Probe Cards
Segment Reporting Information [Line Items]
Revenues	111,606	119,438	318,120	347,559
Systems
Segment Reporting Information [Line Items]
Revenues	23,383	24,297	70,668	68,981
Corporate and Other
Segment Reporting Information [Line Items]
Revenues	0	0	0	0
Gross profit	$ (5,955)	$ (6,379)	$ (17,983)	$ (20,412)
Gross margin	0.00%	0.00%	0.00%	0.00%
Operating income (loss)	$ (20,469)	$ (8,905)	$ (59,647)	$ (27,748)
Operating Segments | Probe Cards
Segment Reporting Information [Line Items]
Revenues	111,606	119,439	318,120	347,559
Gross profit	$ 47,675	$ 51,438	$ 138,182	$ 151,204
Gross margin	42.70%	43.10%	43.40%	43.50%
Operating income (loss)	$ 25,609	$ 17,894	$ 71,326	$ 54,289
Operating Segments | Systems
Segment Reporting Information [Line Items]
Revenues	23,383	24,296	70,668	68,981
Gross profit	$ 11,250	$ 12,571	$ 34,118	$ 36,176
Gross margin	48.10%	51.70%	48.30%	52.40%
Operating income (loss)	$ 4,228	$ 5,277	$ 12,634	$ 14,363

Operating Segments - Revenue by

Operating Segments - Revenue by Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 29, 2018	Sep. 30, 2017	Sep. 29, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 134,989	$ 143,735	$ 388,788	$ 416,540
Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	111,606	119,438	318,120	347,559
Systems
Disaggregation of Revenue [Line Items]
Revenues	23,383	24,297	70,668	68,981
Corporate and Other
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
United States
Disaggregation of Revenue [Line Items]
Revenues	40,127	57,256	106,821	147,494
United States | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	34,398	48,544	89,960	126,110
United States | Systems
Disaggregation of Revenue [Line Items]
Revenues	5,729	8,712	16,861	21,384
Taiwan
Disaggregation of Revenue [Line Items]
Revenues	19,681	17,814	76,980	67,161
Taiwan | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	18,904	15,951	71,300	61,568
Taiwan | Systems
Disaggregation of Revenue [Line Items]
Revenues	777	1,863	5,680	5,593
South Korea
Disaggregation of Revenue [Line Items]
Revenues	21,101	21,762	62,567	63,215
South Korea | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	19,664	21,217	58,250	60,306
South Korea | Systems
Disaggregation of Revenue [Line Items]
Revenues	1,437	545	4,317	2,909
Asia-Pacific
Disaggregation of Revenue [Line Items]
Revenues	29,213	23,800	67,219	70,226
Asia-Pacific | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	22,388	19,136	50,956	53,620
Asia-Pacific | Systems
Disaggregation of Revenue [Line Items]
Revenues	6,825	4,664	16,263	16,606
Europe
Disaggregation of Revenue [Line Items]
Revenues	9,128	12,094	30,150	31,472
Europe | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	5,499	6,015	15,181	17,664
Europe | Systems
Disaggregation of Revenue [Line Items]
Revenues	3,629	6,079	14,969	13,808
Japan
Disaggregation of Revenue [Line Items]
Revenues	14,735	10,456	41,949	35,066
Japan | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	10,462	8,419	31,426	27,219
Japan | Systems
Disaggregation of Revenue [Line Items]
Revenues	4,273	2,037	10,523	7,847
Rest of the world
Disaggregation of Revenue [Line Items]
Revenues	1,004	553	3,102	1,906
Rest of the world | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	291	156	1,047	1,072
Rest of the world | Systems
Disaggregation of Revenue [Line Items]
Revenues	713	397	2,055	834
Products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenues	133,442	142,367	384,289	412,579
Products transferred at a point in time | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	111,020	118,995	316,495	346,191
Products transferred at a point in time | Systems
Disaggregation of Revenue [Line Items]
Revenues	22,422	23,372	67,794	66,388
Services transferred over time
Disaggregation of Revenue [Line Items]
Revenues	1,547	1,368	4,499	3,961
Services transferred over time | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	586	443	1,625	1,368
Services transferred over time | Systems
Disaggregation of Revenue [Line Items]
Revenues	961	925	2,874	2,593
Foundry & Logic
Disaggregation of Revenue [Line Items]
Revenues	61,270	81,914	181,819	244,952
Foundry & Logic | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	61,270	81,914	181,819	244,952
Foundry & Logic | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
DRAM
Disaggregation of Revenue [Line Items]
Revenues	37,359	32,373	105,716	92,798
DRAM | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	37,359	32,373	105,716	92,798
DRAM | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Flash
Disaggregation of Revenue [Line Items]
Revenues	12,977	5,151	30,585	9,809
Flash | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	12,977	5,151	30,585	9,809
Flash | Systems
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Systems
Disaggregation of Revenue [Line Items]
Revenues	23,383	24,297	70,668	68,981
Systems | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	0	0	0	0
Systems | Systems
Disaggregation of Revenue [Line Items]
Revenues	23,383	24,297	70,668	68,981
Operating Segments | Probe Cards
Disaggregation of Revenue [Line Items]
Revenues	111,606	119,439	318,120	347,559
Operating Segments | Systems
Disaggregation of Revenue [Line Items]
Revenues	$ 23,383	$ 24,296	$ 70,668	$ 68,981