Calix (CALX) 10-Q 10 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Apr. 01, 2017	May 03, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	CALIX, INC
Entity Central Index Key	1,406,666
Document Type	10-Q
Document Period End Date	Apr. 1, 2017
Amendment Flag	false
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		49,875,750

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 26,318	$ 50,359
Marketable securities	25,215	27,748
Accounts receivable, net	64,188	51,336
Inventory	46,538	44,545
Deferred cost of revenue	40,454	34,763
Prepaid expenses and other current assets	11,911	10,571
Total current assets	214,624	219,322
Property and equipment, net	18,144	17,984
Goodwill	116,175	116,175
Intangible assets, net	0	813
Other assets	816	1,181
Total assets	349,759	355,475
Current liabilities:
Accounts payable	24,520	23,827
Accrued liabilities	77,015	69,715
Deferred revenue	44,416	27,854
Total current liabilities	145,951	121,396
Long-term portion of deferred revenue	20,876	20,237
Other long-term liabilities	775	878
Total liabilities	167,602	142,511
Commitments and contingencies (See Note 7)
Stockholders’ equity:
Preferred stock, $0.025 par value; 5,000,000 shares authorized; no shares issued and outstanding as of April 1, 2017 and December 31, 2016	0	0
Common stock, $0.025 par value; 100,000,000 shares authorized; 54,956,348 shares issued and 49,626,531 shares outstanding as of April 1, 2017, and 54,722,135 shares issued and 49,392,318 shares outstanding as of December 31, 2016	1,374	1,368
Additional paid-in capital	839,018	836,563
Accumulated other comprehensive loss	(599)	(656)
Accumulated deficit	(617,650)	(584,325)
Treasury stock, 5,329,817 shares as of April 1, 2017 and December 31, 2016	(39,986)	(39,986)
Total stockholders’ equity	182,157	212,964
Total liabilities and stockholders’ equity	$ 349,759	$ 355,475

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Apr. 01, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.025	$ 0.025
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	54,956,348	54,722,135
Common stock, shares outstanding	49,626,531	49,392,318
Treasury stock, shares	5,329,817	5,329,817

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Apr. 01, 2017	Mar. 26, 2016
Revenue:
Systems		$ 91,605	$ 91,680
Services		25,913	6,695
Total revenue		117,518	98,375
Cost of revenue:
Systems	[1]	57,373	47,693
Services	[1]	25,768	5,200
Total cost of revenue		83,141	52,893
Gross profit		34,377	45,482
Operating expenses:
Research and development	[1]	33,808	22,773
Sales and marketing	[1]	22,429	19,062
General and administrative	[1]	10,257	12,684
Amortization of intangible assets		0	1,701
Restructuring charges		699	0
Total operating expenses		67,193	56,220
Loss from operations		(32,816)	(10,738)
Interest and other income (expense), net:
Interest income		88	211
Interest expense		(44)	(164)
Other income (expense), net		120	83
Loss before provision for income taxes		(32,652)	(10,608)
Provision for income taxes		673	121
Net loss		$ (33,325)	$ (10,729)
Net loss per common share:
Basic and diluted (in dollars per share)		$ (0.67)	$ (0.22)
Weighted-average number of shares used to compute net loss per common share:
Basic and diluted (in shares)		49,525	48,591
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available-for-sale marketable securities, net		$ (4)	$ 65
Foreign currency translation adjustments, net		61	(18)
Total other comprehensive income (loss), net of tax		57	47
Comprehensive loss		$ (33,268)	$ (10,682)
[1]	Includes stock-based compensation as follows: Three Months Ended April 1, 2017 and March 26, 2016; Cost of revenue: Systems - $56, $37; Services - $0, $46; Research and development - $1,326, $1,047; Sales and marketing - $1,111, $822; General administrative - $931, $725;

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Systems
Stock-based compensation	$ 116	$ 90
Services
Stock-based compensation	56	37
Research and development
Stock-based compensation	1,326	1,047
Sales and marketing
Stock-based compensation	1,111	822
General and administrative
Stock-based compensation	$ 931	$ 725

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Operating activities:
Net loss	$ (33,325)	$ (10,729)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	2,463	1,955
Loss on retirement of property and equipment	80	0
Amortization of intangible assets	813	3,364
Amortization of premiums related to available-for-sale securities	(5)	114
Stock-based compensation	3,540	2,721
Changes in operating assets and liabilities:
Accounts receivable, net	(12,852)	3,351
Inventory	(1,993)	6,540
Deferred cost of revenue	(5,691)	810
Prepaid expenses and other assets	(968)	(576)
Accounts payable	276	(8,459)
Accrued liabilities	7,110	8,471
Deferred revenue	17,201	(2,195)
Other long-term liabilities	(103)	(98)
Net cash provided by (used in) operating activities	(23,454)	5,269
Investing activities:
Purchases of property and equipment	(2,106)	(1,453)
Purchases of marketable securities	(8,732)	0
Maturities of marketable securities	11,266	7,020
Net cash provided by investing activities	428	5,567
Financing activities:
Proceeds from exercise of stock options	13	14
Payments for repurchases of common stock	0	(12,809)
Taxes paid for awards vested under equity incentive plans	(1,093)	(251)
Net cash used in financing activities	(1,080)	(13,046)
Effect of exchange rate changes on cash and cash equivalents	65	(51)
Net decrease in cash and cash equivalents	(24,041)	(2,261)
Cash and cash equivalents at beginning of period	50,359	23,626
Cash and cash equivalents at end of period	$ 26,318	$ 21,365

Company and Basis of Presentati

Company and Basis of Presentation	3 Months Ended
	Apr. 01, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Company and Basis of Presentation	Company and Basis of Presentation Company Calix, Inc. (together with its subsidiaries, “Calix,” the “Company,” “our,” “we,” or “us”) was incorporated in August 1999, and is a Delaware corporation. The Company is a leading global provider of broadband communications access platforms, systems and software for fiber- and copper-based network architectures and a pioneer in software defined access that enables communications service providers (“CSPs”) to transform their networks and enhance how they connect to their residential and business subscribers. The Company develops and sells carrier-class hardware and software products, referred to as the Calix portfolio that are designed to enhance and transform CSP access networks to meet the changing demands of subscribers rapidly and cost-effectively. The Company enables CSPs to provide a wide range of revenue-generating services, from basic voice and data to advanced broadband services, over legacy and next-generation access networks. The Company focuses solely on CSP access networks, the portion of the network that governs available bandwidth and determines the range and quality of services that can be offered to subscribers. Basis of Presentation The accompanying unaudited condensed consolidated financial statements, including the accounts of Calix, Inc. and its wholly-owned subsidiaries, have been prepared in accordance with the requirements of the U.S. Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. generally accepted accounting principles (“GAAP”) can be condensed or omitted. In the opinion of management, the financial statements include all normal and recurring adjustments that are considered necessary for the fair presentation of the Company’s financial position and operating results. All significant intercompany balances and transactions have been eliminated in consolidation. The Condensed Consolidated Balance Sheet at December 31, 2016 has been derived from the audited financial statements at that date. The results of the Company’s operations can vary during each quarter of the year. Therefore, the results and trends in these interim financial statements may not be the same as those for the full year or any future periods. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016 . The Company’s fiscal year begins on January 1st and ends on December 31st. Quarterly periods are based on a 4-4-5 fiscal calendar with the first, second and third fiscal quarters ending on the 13th Saturday of each fiscal period. As a result, the Company had five more days in the three months ended April 1, 2017 than in the three months ended March 26, 2016 . The preparation of financial statements in conformity with GAAP for interim financial reporting requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates. Prior Period Recast The Company’s revenue from services for the three months ended April 1, 2017 represents more than 10% of its total revenue; hence, the revenue derived from services along with its associated cost of revenue are presented separately in the accompanying Condensed Consolidated Statements of Comprehensive Loss. Services include professional services, software support services for access systems, extended warranty and training services. Accordingly, revenue and cost of revenue for the three months ended March 26, 2016 are recast solely to conform with the current period presentation. The recast does not affect total revenue, total cost of revenue and operating expenses, loss from operations, or net loss.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Apr. 01, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in its Annual Report on Form 10-K for the year ended December 31, 2016 . The Company’s significant accounting policies did not change during the three months ended April 1, 2017 , except for those impacted by the newly adopted accounting standards below. Newly Adopted Accounting Standards Stock-Based Compensation In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which simplifies several aspects of the accounting for employee share-based payment transactions for both public and nonpublic entities, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The Company adopted ASU 2016-09 in the first quarter of fiscal 2017 and had the following impact: a. Accounting for Income Taxes - The primary impact of the adoption was the recognition of excess tax benefits and tax deficiencies through the statement of operations when the awards vest or are settled rather than through paid-in capital. The new guidance eliminates the requirement to delay the recognition of excess tax benefits until it reduces current taxes payable and requires the recognition of excess tax benefits and tax deficiencies in the period they arise. The Company adopted this guidance on a modified retrospective basis beginning on January 1, 2017, and the adoption had a cumulative-effect adjustment to the beginning balance of deferred tax asset and was fully offset by the corresponding valuation allowance as of January 1, 2017. The adoption had no cumulative-effect adjustment on January 1, 2017 accumulated deficit as the Company’s net operating loss carryforwards are offset by a full valuation allowance. b. Classification of Excess Tax Benefits on the Statement of Cash Flows - ASU 2016-09 requires all tax-related cash flows resulting from share-based payments to be reported as operating activities on the statement of cash flows, a change from the current requirement to present windfall tax benefits as an inflow from financing activities and an outflow from operating activities. The Company adopted this guidance prospectively beginning on January 1, 2017. The adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. c. Forfeitures - The Company has historically recognized stock-based compensation expense net of estimated forfeitures on all unvested awards and elected to continuously do so with the adoption of this new guidance. Hence, the adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. d. Minimum Statutory Tax Withholding Requirements - ASU 2016-09 allows companies to withhold an amount up to the employee’s maximum individual tax rate in the relevant jurisdiction without resulting in liability classification of the award. The Company adopted this guidance using a modified retrospective approach. The adoption had no impact on the January 1, 2017 accumulated deficit as the Company had no outstanding liability awards that would otherwise qualify for equity classification under this new guidance. e. Classification of Employee Taxes Paid on the Statement of Cash Flows When an Employer Withholds Shares for Tax-Withholding Purposes - ASU 2016-09 clarifies that all cash payments made to taxing authorities on the employees’ behalf for withheld shares should be presented as financing activities on the statement of cash flows. The Company has historically presented the taxes paid related to net share settlement of equity awards as a financing activity on the statements of cash flows. Hence, the adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. Inventory In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (“ASU 2015-11”), which requires measurement of inventory at lower of cost and net realizable value, versus lower of cost or market. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company adopted ASU 2015-11 prospectively beginning on January 1, 2017. The adoption of this standard had no material impact on the Company’s consolidated financial statements. Recent Accounting Pronouncements Not Yet Adopted Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires recognition of an asset and liability for lease arrangements longer than twelve months. ASU 2016-02 will be effective for the Company beginning in the first quarter of fiscal 2019. Early application is permitted, and it is required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company expects its assets and liabilities to increase as a result of the adoption of this standard. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. Revenue from Contracts with Customers In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. Additionally, it supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts, and creates new Subtopic 340-40, Other Assets and Deferred Costs-Contracts with Customers. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the previous guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. On August 12, 2015, the FASB issued Accounting Standards Update No. 2015-14, Revenue from Contracts with Customers (Topic 606), Deferral of the Effective Date (“ASU 2015-14”) to defer the effective date of ASU 2014-09 by one year. ASU 2015-14 permits early adoption of the new revenue standard, but not before its original effective date. In April 2016, the FASB issued Accounting Standards Update No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing (“ASU 2016-10”) which further clarifies guidance related to identifying performance obligations and licensing implementation guidance contained in ASU 2014-09. In May 2016, the FASB issued Accounting Standards Update No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”) which addresses narrow-scope improvements to the guidance on collectibility, non-cash consideration, and completed contracts at transition and provides a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The new standard permits adoption either by using (i) a full retrospective approach for all periods presented in the period of adoption or (ii) a modified retrospective approach with the cumulative effect of initially applying the new standard recognized at the date of initial application and providing certain additional disclosures. The Company has not yet determined which transition method it will adopt. Its determination will depend on a number of factors, such as the significance of the impact of the new standard on its financial results, system readiness and its ability to accumulate and analyze the information necessary to assess the impact on prior period financial statements, as necessary. The standard will be effective for the Company in the first quarter of fiscal 2018, with early adoption permitted for annual reporting period beginning in the first quarter of fiscal 2017. The Company is not planning to early adopt, and accordingly, it will adopt the new standard effective January 1, 2018. The Company is in the initial stages of its evaluation of the impact of the new standard on its accounting policies, processes, and system requirements. The Company has assigned internal resources in addition to the engagement of third party service providers to assist in its evaluation. Additionally, the Company expects to make investments in new systems or enhancement of existing systems to enable timely and accurate reporting under the new standard. While the Company continues to perform further assessment of all potential impacts under the new standard, the Company expects the timing of revenue recognition to be accelerated for certain performance obligations related to certain revenue arrangements which are currently deferred until customer acceptance. Depending on the outcome of the Company’s final evaluation, the timing of when revenue is recognized could change significantly for those revenue arrangements under the new standard. As part of its preliminary evaluation, the Company also considered the impact of the guidance in ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers with respect to capitalization and amortization of incremental costs of obtaining a contract. As a result of this new guidance, the Company may need to capitalize additional costs of obtaining a contract, including sales commissions, as the new cost guidance requires the capitalization of all incremental costs incurred to obtain a contract with a customer that it would not have incurred if the contract had not been obtained, provided it expects to recover the costs. Accordingly, the Company may need to defer certain sales commissions and amortize them over the period that the related revenue is recognized. While the Company continues to assess all the potential impacts of the new standard, including the areas described above, and anticipates this standard could have a material impact on its consolidated financial statements, the Company is not able to quantify or cannot reasonably estimate quantitative information related to the impact of the new standard on its consolidated financial statements at this time. Concentration of Customer Risk The Company had two customers that each accounted for more than 10% of its total revenue for the three months ended April 1, 2017 and March 26, 2016 . These two customers together represented 55% and 29% of the Company’s total revenue for the three months ended April 1, 2017 and March 26, 2016 , respectively. Each of these two customers represented 10% or more of the Company’s accounts receivable as of April 1, 2017 and December 31, 2016 .

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	3 Months Ended
	Apr. 01, 2017
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The Company has invested its excess cash primarily in money market funds and highly liquid marketable securities such as corporate debt instruments, commercial paper, and U.S. government agency securities. The Company considers all investments with maturities of three months or less when purchased to be cash equivalents. Marketable securities represent highly liquid corporate debt instruments, commercial paper, and U.S. government agency securities with maturities greater than 90 days at date of purchase. Marketable securities with maturities greater than one year are classified as current because management considers all marketable securities to be available for current operations. Cash equivalents are stated at amounts that approximate fair value based on quoted market prices. Marketable securities are recorded at their fair values. The Company’s investments have been classified and accounted for as available-for-sale. Such investments are recorded at fair value and unrealized holding gains and losses are reported as a separate component of accumulated other comprehensive income (loss) in the stockholders’ equity until realized. Realized gains and losses on sales of marketable securities, if any, are determined on the specific identification method and are reclassified from accumulated other comprehensive income (loss) to results of operations as other income (expense). The Company, to date, has not determined that any of the unrealized losses on its investments are considered to be other-than-temporary. The Company reviews its investment portfolio to determine if any security is other-than-temporarily impaired, which would require the Company to record an impairment charge in the period any such determination is made. In making this judgment, the Company evaluates, among other things: the duration and extent to which the fair value of a security is less than its cost; the financial condition of the issuer and any changes thereto; and the Company’s intent and ability to hold its investment for a period of time sufficient to allow for any anticipated recovery in market value, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The Company has evaluated its investments as of April 1, 2017 and has determined that no investments with unrealized losses are other-than-temporarily impaired. No investments have been in a continuous loss position for greater than one year. Cash, cash equivalents and marketable securities consisted of the following (in thousands): April 1, December 31, Cash and cash equivalents: Cash $ 17,675 $ 34,340 Money market funds 8,197 15,020 Corporate debt securities 446 — Commercial paper — 999 Total cash and cash equivalents 26,318 50,359 Marketable securities: Corporate debt securities 10,843 17,272 Commercial paper 10,174 6,275 U.S. government agency securities 4,198 4,201 Total marketable securities 25,215 27,748 Total cash, cash equivalents and marketable securities $ 51,533 $ 78,107 The carrying amounts of the Company’s money market funds approximate their fair values due to their nature, duration and short maturities. As of April 1, 2017 , the amortized cost and fair value of marketable securities were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 10,851 $ — $ (8 ) $ 10,843 Commercial paper 10,174 — — 10,174 U.S. government agency securities 4,200 — (2 ) 4,198 Total marketable securities $ 25,225 $ — $ (10 ) $ 25,215 As of December 31, 2016 , the amortized cost and fair value of marketable securities were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 17,279 $ 1 $ (8 ) $ 17,272 Commercial paper 6,275 — — 6,275 U.S. government agency securities 4,200 1 — 4,201 Total marketable securities $ 27,754 $ 2 $ (8 ) $ 27,748 As of April 1, 2017 , the amortized cost and fair value of marketable securities by contractual maturity were as follows (in thousands): Amortized Cost Fair Value Due in 1 year or less $ 25,225 $ 25,215

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Apr. 01, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements The Company measures its cash equivalents and marketable securities at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. The Company utilizes the following three-tier value hierarchy which prioritizes the inputs used in measuring fair value: Level 1 – Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 – Observable inputs other than quoted prices included in Level 1 for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-driven valuations in which all significant inputs and significant value drivers are observable in active markets. Level 3 – Unobservable inputs to the valuation derived from fair valuation techniques in which one or more significant inputs or significant value drivers are unobservable. The following table sets forth the Company’s financial assets measured at fair value on a recurring basis as of April 1, 2017 and December 31, 2016 , based on the three-tier fair value hierarchy (in thousands): As of April 1, 2017 Level 1 Level 2 Total Money market funds $ 8,197 $ — $ 8,197 Corporate debt securities — 11,289 11,289 Commercial paper — 10,174 10,174 U.S. government agency securities — 4,198 4,198 Total $ 8,197 $ 25,661 $ 33,858 As of December 31, 2016 Level 1 Level 2 Total Money market funds $ 15,020 $ — $ 15,020 Corporate debt securities — 17,272 17,272 Commercial paper — 7,274 7,274 U.S. government agency securities — 4,201 4,201 Total $ 15,020 $ 28,747 $ 43,767 The fair values of money market funds classified as Level 1 were derived from quoted market prices as active markets for these instruments exist. The fair values of corporate debt securities, commercial paper and U.S. government agency securities classified as Level 2 were derived from quoted market prices for similar instruments indexed to prevailing market yield rates. The Company has no level 3 financial assets. The Company did not have any transfers between Level 1 and Level 2 of the fair value hierarchy during the three months ended April 1, 2017 and March 26, 2016 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Apr. 01, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill Goodwill was recorded as a result of the Company’s acquisitions of Occam Networks, Inc. (“Occam”) in February 2011 and Optical Solutions, Inc. in February 2006. This goodwill is not deductible for tax purposes, and there have been no adjustments to goodwill since the acquisition dates. Goodwill is not amortized but instead is subject to an annual impairment test or more frequently if events or changes in circumstances indicate that it may be impaired. The Company evaluates goodwill on an annual basis at the end of the second quarter of each year. Management has determined that the Company operates as a single reporting unit and, therefore, evaluates goodwill impairment at the enterprise level. Management assessed qualitative factors to determine whether it was more likely than not (that is, a likelihood of more than 50 percent) that the fair value of the Company was less than its carrying amount, including goodwill, as of June 25, 2016 . In assessing the qualitative factors, management considered the impact of these key factors: macro-economic conditions, industry and market environment, overall financial performance of the Company, cash flow from operating activities, market capitalization and stock price. Management concluded that the fair value of the Company was more likely than not greater than its carrying amount as of June 25, 2016 . As such, it was not necessary to perform the two-step goodwill impairment test at the time. There have been no significant events or changes in circumstances subsequent to the 2016 annual impairment test that would more likely than not indicate that the carrying value of goodwill may have been impaired as of April 1, 2017 . Therefore, there was no impairment to the carrying value of the Company’s goodwill as of April 1, 2017 . Intangible Assets Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of April 1, 2017 and December 31, 2016 are disclosed in the following table (in thousands): April 1, 2017 December 31, 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (68,964 ) $ — $ 68,964 $ (68,151 ) $ 813 Customer relationships 54,740 (54,740 ) — 54,740 (54,740 ) — Total intangible assets, excluding goodwill $ 123,704 $ (123,704 ) $ — $ 123,704 $ (122,891 ) $ 813 Amortization expense was $0.8 million and $3.4 million for the three months ended April 1, 2017 and March 26, 2016 , respectively.

Balance Sheet Details

Balance Sheet Details	3 Months Ended
	Apr. 01, 2017
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): April 1, December 31, Accounts receivable $ 66,142 $ 52,792 Allowance for doubtful accounts (477 ) (518 ) Product return reserve (1,477 ) (938 ) Accounts receivable, net $ 64,188 $ 51,336 Inventory consisted of the following (in thousands): April 1, December 31, Raw materials $ 1,502 $ 1,827 Finished goods 45,036 42,718 Total inventory $ 46,538 $ 44,545 Property and equipment, net consisted of the following (in thousands): April 1, December 31, Test equipment $ 44,466 $ 43,580 Computer equipment and software 31,785 30,306 Furniture and fixtures 2,709 2,831 Leasehold improvements 6,827 6,898 Total 85,787 83,615 Accumulated depreciation and amortization (67,643 ) (65,631 ) Property and equipment, net $ 18,144 $ 17,984 Accrued liabilities consisted of the following (in thousands): April 1, December 31, Advance customer payments $ 22,946 $ 20,726 Accrued compensation and related benefits 22,193 19,541 Accrued warranty and retrofit 10,778 12,214 Accrued professional and consulting fees 9,952 8,205 Accrued excess and obsolete inventory at contract manufacturers 2,415 1,327 Accrued customer rebates 1,425 1,931 Accrued insurance 756 804 Accrued restructuring charges 699 — Income taxes payable 20 231 Accrued other 5,831 4,736 Total accrued liabilities $ 77,015 $ 69,715 Advance customer payments as of April 1, 2017 and December 31, 2016 primarily included $21.5 million and $20.3 million , respectively, which the Company received as payments in advance of completion of final customer acceptance of the products and services provided in connection with network improvement projects for a customer. Deferred revenue consisted of the following (in thousands): April 1, December 31, Current: Product and services $ 41,152 $ 24,472 Extended warranty 3,264 3,382 44,416 27,854 Non-current: Product and services 38 22 Extended warranty 20,838 20,215 20,876 20,237 Total deferred revenue $ 65,292 $ 48,091 Deferred cost of revenue consisted of costs incurred for products and services for which revenues have been deferred or not yet earned.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Apr. 01, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments The Company’s principal commitments consist of obligations under operating leases for office space and non-cancelable outstanding purchase obligations. These commitments as of December 31, 2016 are disclosed in the Company’s Annual Report on Form 10-K, and have not changed materially during the three months ended April 1, 2017 . Contingencies The Company evaluates the circumstances regarding outstanding and potential litigation and other contingencies on a quarterly basis to determine whether there is at least a reasonable possibility that a loss exists requiring accrual or disclosure, and if so, whether an estimate of the possible loss or range of loss can be made, or whether such an estimate cannot be made. When a loss is probable and reasonably estimable, the Company accrues for such amount based on its estimate of the probable loss considering information available at the time. When a loss is reasonably possible, the Company discloses the estimated possible loss or range of loss in excess of amounts accrued if material. Except as otherwise disclosed below, the Company does not believe that there was a reasonable possibility that a material loss may have been incurred during the period presented with respect to the matters disclosed. Accrued Warranty and Retrofit The Company provides a standard warranty for its hardware products. Hardware generally has a one -, three -, or five -year standard warranty from the date of shipment. Under certain circumstances, the Company also provides fixes on specifically identified performance failures for products that are outside of the standard warranty period and recognizes estimated costs related to retrofit activities upon identification of such product failures. The Company accrues for potential warranty and retrofit claims based on the Company’s historical product failure rates and historical costs incurred in correcting product failures along with other relevant information related to any specifically identified product failures. The Company’s warranty and retrofit accruals are based on estimates of losses that are probable based on information available. The adequacy of the accrual is reviewed on a periodic basis and adjusted, if necessary, based on additional information as it becomes available. Changes in the Company’s warranty and retrofit reserves in the periods as indicated were as follows (in thousands): Three Months Ended April 1, March 26, Balance at beginning of period $ 12,214 $ 9,564 Provision for warranty and retrofit charged to cost of revenue 1,862 580 Utilization of reserve (3,298 ) (619 ) Adjustments to pre-existing reserve — (373 ) Balance at end of period $ 10,778 $ 9,152 Litigation From time to time, the Company is involved in various legal proceedings arising from the normal course of business activities. The Company is not currently a party to any legal proceedings that, if determined adversely to the Company, in management’s opinion, are currently expected to individually or in the aggregate have a material adverse effect on the Company’s business, operating results or financial condition taken as a whole. Guarantees The Company from time to time enters into contracts that require it to indemnify various parties against claims from third parties. These contracts primarily relate to (i) certain real estate leases, under which the Company may be required to indemnify property owners for environmental and other liabilities, and other claims arising from the Company’s use of the applicable premises, (ii) agreements with the Company’s officers, directors, and certain employees, under which the Company may be required to indemnify such persons for liabilities arising out of their relationship with the Company, (iii) contracts under which the Company may be required to indemnify customers against third-party claims that a Company product infringes a patent, copyright, or other intellectual property right and (iv) procurement or license agreements, under which the Company may be required to indemnify licensors or vendors for certain claims that may be brought against them arising from the Company’s acts or omissions with respect to the supplied products or technology. Because any potential obligation associated with these types of contractual provisions are not quantified or stated, the overall maximum amount of the obligation cannot be reasonably estimated. Historically, the Company has not been required to make payments under these obligations, and no liabilities have been recorded for these obligations in the accompanying Condensed Consolidated Balance Sheets.

Net Loss per Common Share

Net Loss per Common Share	3 Months Ended
	Apr. 01, 2017
Earnings Per Share [Abstract]
Net Loss per Common Share	Net Loss per Common Share The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated (in thousands, except per share data): Three Months Ended April 1, March 26, Numerator: Net loss $ (33,325 ) $ (10,729 ) Denominator: Weighted-average common shares outstanding 49,525 48,591 Basic and diluted net loss per common share $ (0.67 ) $ (0.22 ) Potentially dilutive shares, weighted average 6,145 5,500 Potentially dilutive shares have been excluded from the computation of diluted net loss per common share when their effect is antidilutive. These antidilutive shares were primarily from stock options, restricted stock units and performance restricted stock units. For each of the periods presented where the Company reported a net loss, the effect of all potentially dilutive securities would be antidilutive, and as a result diluted net loss per common share is the same as basic net loss per common share.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Apr. 01, 2017
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Equity Incentive Plans The Company currently maintains two equity incentive plans, the 2002 Stock Plan and the 2010 Equity Incentive Award Plan (together, the “Plans”). These plans were approved by the stockholders and are described in the Company’s Annual Report on Form 10-K filed with the SEC on February 28, 2017 . The Company also maintains a Long Term Incentive Program under the 2010 Equity Incentive Award Plan. Under the Long Term Incentive Program, certain key employees of the Company are eligible for equity awards based on the Company’s stock price performance. To date, awards granted under the Plans consist of stock options, restricted stock units (“RSUs”), and performance restricted stock units (“PRSUs”). Stock Options During the three months ended April 1, 2017 , no stock options were granted. During the three months ended April 1, 2017 , 2,000 stock options were exercised at a weighted-average exercise price of $6.54 per share. As of April 1, 2017 , unrecognized stock-based compensation expense of $3.2 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.8 years. Restricted Stock Units During the three months ended April 1, 2017 , 203,100 RSUs were granted with a weighted-average grant date fair value of $7.00 per share. During the three months ended April 1, 2017 , 52,161 RSUs vested, net of shares withheld at the then-current value equivalent to the employees’ minimum statutory obligation for applicable income and other employment taxes, and were converted to an equivalent number of shares of common stock. Taxes withheld from employees of $0.3 million were remitted to the relevant taxing authorities during the three months ended April 1, 2017 . As of April 1, 2017 , unrecognized stock-based compensation expense of $12.6 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 2.4 years. Performance Restricted Stock Units In 2012, 2013 and 2014, the Company granted PRSUs to its executives with two -year and three -year performance periods. The performance criterion is based on the relative total shareholder return (“TSR”) of Calix common stock as compared to the TSR of the Company’s peer group and accounted for as a market condition. The TSR is calculated by dividing (a) the average closing trading price for the 90 -day period ending on the last day of the applicable performance period by (b) the average closing trading price for the 90 -day period immediately preceding the first day of the applicable performance period. This TSR is then used to derive the achievement ratio, which is then multiplied by the number of units in the grant to derive the common stock to be issued for each performance period, which may equal from zero percent ( 0% ) to two hundred percent ( 200% ) of the target award. In 2016, the Company granted PRSUs to its executives with a one -year performance period and a subsequent two -year service period. The performance target for these particular performance-based awards is based on the Company’s revenue during the performance period and accounted for as a performance condition. After the one -year performance period, if the performance target is met and subject to certification by the Compensation Committee of the Company’s board of directors, each PRSU award shall vest with respect to 50% of the PRSUs subject to the award in February 2017, 25% in February 2018 and 25% in February 2019, subject to the executive’s continuous service with the Company from the grant date through the respective vesting dates. If the performance target is not met, all PRSUs granted under this award shall be immediately forfeited and canceled without vesting of any shares. During the three months ended April 1, 2017 , 300,000 PRSUs vested and were converted into 180,052 shares of common stock, net of shares withheld at the then-current value equivalent to the employees’ minimum statutory obligation for applicable income and other employment taxes. Taxes withheld from employees of $0.8 million were remitted to the relevant taxing authorities during the three months ended April 1, 2017 . As of April 1, 2017 , unrecognized stock-based compensation expense of $0.7 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 1.4 years. Employee Stock Purchase Plan The Company’s Amended and Restated Employee Stock Purchase Plan (“ESPP”) allows employees to purchase shares of the Company’s common stock through payroll deductions of up to 15 percent of their annual compensation subject to certain Internal Revenue Code limitations. In addition, no participant may purchase more than 2,000 shares of common stock in each offering period. Prior to 2015, the offering periods under the 2010 ESPP were six-month periods commencing on June 1 and December 1 of each year. In January 2015, the Compensation Committee of the Company’s board of directors approved a change in those six-month period commencement dates to November 2 and May 2 of each year, effective November 2, 2015. In July 2016, the Compensation Committee of the Company’s board of directors approved a change in those six-month period commencement dates to May 15 and November 15 of each year, effective May 15, 2017. The ending date of the ESPP offering period which commenced on November 2, 2016 will be extended until May 14, 2017 as a result of this change. The price of common stock purchased under the 2010 ESPP is 85 percent of the lower of the fair market value of the common stock on the commencement date and the end date of each six -month offering period. As of April 1, 2017 , there were 119,228 shares available for issuance under the ESPP. There were no shares purchased under the ESPP during the three months ended April 1, 2017 . As of April 1, 2017 , unrecognized stock-based compensation expense of $0.2 million related to the ESPP is expected to be recognized over a remaining service period of 1.5 months. Stock-Based Compensation Expense Stock-based compensation expense associated with stock options, RSUs, PRSUs, and purchase rights under the ESPP is measured at the grant date based on the fair value of the award, and is recognized, net of forfeitures, as expense over the remaining requisite service period on a straight-line basis. The Company values RSUs at the closing market price of the Company’s common stock on the date of grant. Stock-based compensation expense associated with PRSUs with graded vesting features and which contain both a performance and a service condition is measured based on the closing market price of the Company’s common stock on the date of grant, and is recognized, net of forfeitures, as expense over the requisite service period using the graded vesting attribution method. Compensation expense is only recognized if the Company has determined that it is probable that the performance condition will be met. The Company reassesses the probability of vesting at each reporting period and adjusts compensation expense based on its probability assessment. In February 2017, the Compensation Committee of the Company’s board of directors determined that the performance condition related to PRSUs granted to executives in 2016 was met based on the Company’s actual revenue recognized during fiscal 2016. The fair value of PRSUs with a market condition is estimated on the date of award, using a Monte Carlo simulation model to estimate the TSR of the Company’s stock in relation to the peer group over each performance period. Compensation cost on PRSUs with a market condition is not adjusted for subsequent changes in the Company’s stock performance or the level of ultimate vesting. Stock Repurchase On April 26, 2015, the Company’s board of directors approved a program to repurchase up to $40 million of its common stock from time to time. This stock repurchase program commenced in May 2015 and was completed in March 2016. Under this program, stock was purchasable in open market or private transactions, through block trades, and/or pursuant to any trading plan adopted in accordance with Rule 10b5-1 of the Securities Exchange Act of 1934, as amended (“Exchange Act”) and any open market purchases were to be made in accordance with the limitations set out in Rule 10b-18 of the Exchange Act. The decision to consummate any repurchases (including any decision to adopt a 10b5-1 plan for this purpose) were to be made at management’s discretion at prices management considered to be attractive and in the best interests of the Company and its stockholders. In March 2016, the Company completed the $40 million stock repurchase program and has repurchased a total of 5,329,817 shares of common stock from May 2015 to March 2016 at an average price of $7.50 per share. The Company uses the cost method to account for common stock repurchases held in treasury. The price paid for the stock is charged to the treasury stock account shown separately within stockholders’ equity as a contra-equity account.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	3 Months Ended
	Apr. 01, 2017
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The table below summarizes the changes in accumulated other comprehensive loss by component for the periods indicated (in thousands): Three Months Ended April 1, 2017 March 26, 2016 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (6 ) $ (650 ) $ (656 ) $ (94 ) $ (101 ) $ (195 ) Other comprehensive income (loss) (4 ) 61 57 65 (18 ) 47 Balance at end of period $ (10 ) $ (589 ) $ (599 ) $ (29 ) $ (119 ) $ (148 ) Realized gains and losses on sales of available-for-sale marketable securities, if any, are reclassified from accumulated other comprehensive loss to “Other income (expense)” in the accompanying Condensed Consolidated Statements of Comprehensive Loss.

Credit Facility

Credit Facility	3 Months Ended
	Apr. 01, 2017
Line of Credit Facility [Abstract]
Credit Facility	Credit Facility The Company entered into a credit agreement with Bank of America, N.A. on July 29, 2013 (as amended on December 23, 2015, the “Credit Agreement”). The Credit Agreement is structured such that other financial institutions can at a later time become party to the Credit Agreement through an amendment via a syndication process (collectively, together with Bank of America, N.A., the “Lenders”). The Credit Agreement provides for a revolving facility in the aggregate principal amount of up to $50.0 million , with any borrowings limited to a maximum consolidated leverage ratio of consolidated funded indebtedness to consolidated EBITDA (as defined in the Credit Agreement). In addition, the Credit Agreement includes a $20.0 million sublimit for the issuance of letters of credit and a $10.0 million sublimit for a swingline facility. Subject to customary conditions, up to $25.0 million of the revolving facility may be converted to a term loan facility at any time prior to the maturity of the revolving facility. The revolving facility matures on September 30, 2018 . The credit facility is secured by substantially all of the assets of the Company, including its intellectual property. Proceeds of the credit facility may be used for general corporate purposes and permitted acquisitions. Loans under the credit facility bear interest at an annual rate equal to the base rate plus 0.75% to 1.25% or LIBOR plus 2.00% to 2.50% based on a consolidated leverage ratio of consolidated funded indebtedness to consolidated EBITDA (as defined in the Credit Agreement). Interest on the revolving facility is due quarterly, and any outstanding interest and principal is due on the maturity date of the revolving facility. The Company is required to repay principal on a term loan in twenty equal quarterly payments from the date the Company enters into a term loan, and all outstanding principal and accrued interest is due on the revolving facility maturity date. Swingline loans must be repaid on the earlier of (i) ten business days after a loan is made and (ii) the revolving facility maturity date. The Company is also required to pay commitment fees of 0.25% per year on any unused portions of this facility. The Credit Agreement includes affirmative and negative covenants applicable to the Company that are typical for credit facilities of this type. Furthermore, the Credit Agreement requires the Company to maintain certain financial covenants, including a maximum consolidated leverage ratio, and a minimum consolidated liquidity ratio of cash, cash equivalents and accounts receivable to consolidated funded indebtedness. As of April 1, 2017 , the Company was in compliance with these requirements. The Credit Agreement also includes customary events of default, the occurrence and continuation of which would provide the Lenders with the right to demand immediate repayment of any principal and unpaid interest under the credit facility, and to exercise remedies against us and the collateral securing the loans under the credit facility. As of April 1, 2017 , no revolving loans were drawn under the Credit Agreement and, based on the consolidated leverage ratio requirements that limit available funds under the Credit Agreement, the Company has no funds available for borrowing under the Credit Agreement as of April 1, 2017 .

Income Taxes

Income Taxes	3 Months Ended
	Apr. 01, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended April 1, March 26, Provision for income taxes $ 673 $ 121 Effective tax rate (2.1 )% (1.1 )% The income tax provision for the three months ended April 1, 2017 and March 26, 2016 consisted primarily of foreign income taxes. The effective tax rate for the three months ended April 1, 2017 and March 26, 2016 was determined using an estimated annual effective tax rate adjusted for discrete items, if any, that occurred during the respective periods. The Company’s effective tax rate for the three months ended April 1, 2017 and March 26, 2016 is impacted by the change in foreign income tax expense. Deferred tax assets are recognized if realization of such assets is more likely than not. The Company has established and continues to maintain a full valuation allowance against its net deferred tax assets, with the exception of certain foreign deferred tax assets, as the Company does not believe that realization of those assets is more likely than not . The Company’s effective tax rate may be subject to fluctuation during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as the mix of forecasted pre-tax earnings in the various jurisdictions in which it operates, valuation allowances against deferred tax assets, the recognition or de-recognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where it conducts business .

Restructuring Charges

Restructuring Charges	3 Months Ended
	Apr. 01, 2017
Restructuring and Related Activities [Abstract]
Restructuring Charges	Restructuring Charges The Company adopted a restructuring plan in March 2017. This restructuring plan realigns the Company’s business, increasing its focus towards its investments in innovative software defined access systems and software, while reducing its cost structure in traditional systems business. The Company began to take action under this plan beginning in March 2017 and recognized approximately $0.7 million of restructuring charges for the three months ended April 1, 2017 consisting primarily of severance and other one-time termination benefits, presented separately under operating expenses in the accompanying Condensed Consolidated Statements of Comprehensive Loss. The following table summarizes the activities related to the restructuring charges pursuant to the above restructuring plan (in thousands): Three Months Ended April 1, 2017 Liability at beginning of period $ — Restructuring charges for the period 699 Cash payments — Liability at end of period $ 699 The Company currently estimates that this plan will result in pre-tax restructuring charges totaling up to $6.8 million with approximately up to $6.1 million of additional charges expected to be recognized during the rest of fiscal 2017. These charges are primarily cash-based.

Significant Accounting Polici20

Significant Accounting Policies (Policies)	3 Months Ended
	Apr. 01, 2017
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Newly Adopted Accounting Standards Stock-Based Compensation In March 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”), which simplifies several aspects of the accounting for employee share-based payment transactions for both public and nonpublic entities, including the accounting for income taxes, forfeitures, and statutory tax withholding requirements, as well as classification in the statement of cash flows. The Company adopted ASU 2016-09 in the first quarter of fiscal 2017 and had the following impact: a. Accounting for Income Taxes - The primary impact of the adoption was the recognition of excess tax benefits and tax deficiencies through the statement of operations when the awards vest or are settled rather than through paid-in capital. The new guidance eliminates the requirement to delay the recognition of excess tax benefits until it reduces current taxes payable and requires the recognition of excess tax benefits and tax deficiencies in the period they arise. The Company adopted this guidance on a modified retrospective basis beginning on January 1, 2017, and the adoption had a cumulative-effect adjustment to the beginning balance of deferred tax asset and was fully offset by the corresponding valuation allowance as of January 1, 2017. The adoption had no cumulative-effect adjustment on January 1, 2017 accumulated deficit as the Company’s net operating loss carryforwards are offset by a full valuation allowance. b. Classification of Excess Tax Benefits on the Statement of Cash Flows - ASU 2016-09 requires all tax-related cash flows resulting from share-based payments to be reported as operating activities on the statement of cash flows, a change from the current requirement to present windfall tax benefits as an inflow from financing activities and an outflow from operating activities. The Company adopted this guidance prospectively beginning on January 1, 2017. The adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. c. Forfeitures - The Company has historically recognized stock-based compensation expense net of estimated forfeitures on all unvested awards and elected to continuously do so with the adoption of this new guidance. Hence, the adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. d. Minimum Statutory Tax Withholding Requirements - ASU 2016-09 allows companies to withhold an amount up to the employee’s maximum individual tax rate in the relevant jurisdiction without resulting in liability classification of the award. The Company adopted this guidance using a modified retrospective approach. The adoption had no impact on the January 1, 2017 accumulated deficit as the Company had no outstanding liability awards that would otherwise qualify for equity classification under this new guidance. e. Classification of Employee Taxes Paid on the Statement of Cash Flows When an Employer Withholds Shares for Tax-Withholding Purposes - ASU 2016-09 clarifies that all cash payments made to taxing authorities on the employees’ behalf for withheld shares should be presented as financing activities on the statement of cash flows. The Company has historically presented the taxes paid related to net share settlement of equity awards as a financing activity on the statements of cash flows. Hence, the adoption of ASU 2016-09 as it relates to this matter had no impact to the Company’s consolidated financial statements. Inventory In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory (“ASU 2015-11”), which requires measurement of inventory at lower of cost and net realizable value, versus lower of cost or market. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. The Company adopted ASU 2015-11 prospectively beginning on January 1, 2017. The adoption of this standard had no material impact on the Company’s consolidated financial statements. Recent Accounting Pronouncements Not Yet Adopted Leases In February 2016, the FASB issued Accounting Standards Update No. 2016-02, Leases (Topic 842) (“ASU 2016-02”), which requires recognition of an asset and liability for lease arrangements longer than twelve months. ASU 2016-02 will be effective for the Company beginning in the first quarter of fiscal 2019. Early application is permitted, and it is required to recognize and measure leases at the beginning of the earliest period presented using a modified retrospective approach. The Company expects its assets and liabilities to increase as a result of the adoption of this standard. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. Revenue from Contracts with Customers In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. Additionally, it supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts, and creates new Subtopic 340-40, Other Assets and Deferred Costs-Contracts with Customers. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the previous guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. On August 12, 2015, the FASB issued Accounting Standards Update No. 2015-14, Revenue from Contracts with Customers (Topic 606), Deferral of the Effective Date (“ASU 2015-14”) to defer the effective date of ASU 2014-09 by one year. ASU 2015-14 permits early adoption of the new revenue standard, but not before its original effective date. In April 2016, the FASB issued Accounting Standards Update No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing (“ASU 2016-10”) which further clarifies guidance related to identifying performance obligations and licensing implementation guidance contained in ASU 2014-09. In May 2016, the FASB issued Accounting Standards Update No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients (“ASU 2016-12”) which addresses narrow-scope improvements to the guidance on collectibility, non-cash consideration, and completed contracts at transition and provides a practical expedient for contract modifications at transition and an accounting policy election related to the presentation of sales taxes and other similar taxes collected from customers. The new standard permits adoption either by using (i) a full retrospective approach for all periods presented in the period of adoption or (ii) a modified retrospective approach with the cumulative effect of initially applying the new standard recognized at the date of initial application and providing certain additional disclosures. The Company has not yet determined which transition method it will adopt. Its determination will depend on a number of factors, such as the significance of the impact of the new standard on its financial results, system readiness and its ability to accumulate and analyze the information necessary to assess the impact on prior period financial statements, as necessary. The standard will be effective for the Company in the first quarter of fiscal 2018, with early adoption permitted for annual reporting period beginning in the first quarter of fiscal 2017. The Company is not planning to early adopt, and accordingly, it will adopt the new standard effective January 1, 2018. The Company is in the initial stages of its evaluation of the impact of the new standard on its accounting policies, processes, and system requirements. The Company has assigned internal resources in addition to the engagement of third party service providers to assist in its evaluation. Additionally, the Company expects to make investments in new systems or enhancement of existing systems to enable timely and accurate reporting under the new standard. While the Company continues to perform further assessment of all potential impacts under the new standard, the Company expects the timing of revenue recognition to be accelerated for certain performance obligations related to certain revenue arrangements which are currently deferred until customer acceptance. Depending on the outcome of the Company’s final evaluation, the timing of when revenue is recognized could change significantly for those revenue arrangements under the new standard. As part of its preliminary evaluation, the Company also considered the impact of the guidance in ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers with respect to capitalization and amortization of incremental costs of obtaining a contract. As a result of this new guidance, the Company may need to capitalize additional costs of obtaining a contract, including sales commissions, as the new cost guidance requires the capitalization of all incremental costs incurred to obtain a contract with a customer that it would not have incurred if the contract had not been obtained, provided it expects to recover the costs. Accordingly, the Company may need to defer certain sales commissions and amortize them over the period that the related revenue is recognized. While the Company continues to assess all the potential impacts of the new standard, including the areas described above, and anticipates this standard could have a material impact on its consolidated financial statements, the Company is not able to quantify or cannot reasonably estimate quantitative information related to the impact of the new standard on its consolidated financial statements at this time.

Cash, Cash Equivalents and Ma21

Cash, Cash Equivalents and Marketable Securities (Tables)	3 Months Ended
	Apr. 01, 2017
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash, cash equivalents and marketable securities consisted of the following (in thousands): April 1, December 31, Cash and cash equivalents: Cash $ 17,675 $ 34,340 Money market funds 8,197 15,020 Corporate debt securities 446 — Commercial paper — 999 Total cash and cash equivalents 26,318 50,359 Marketable securities: Corporate debt securities 10,843 17,272 Commercial paper 10,174 6,275 U.S. government agency securities 4,198 4,201 Total marketable securities 25,215 27,748 Total cash, cash equivalents and marketable securities $ 51,533 $ 78,107
Amortized cost and fair value of marketable securities	As of April 1, 2017 , the amortized cost and fair value of marketable securities were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 10,851 $ — $ (8 ) $ 10,843 Commercial paper 10,174 — — 10,174 U.S. government agency securities 4,200 — (2 ) 4,198 Total marketable securities $ 25,225 $ — $ (10 ) $ 25,215 As of December 31, 2016 , the amortized cost and fair value of marketable securities were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 17,279 $ 1 $ (8 ) $ 17,272 Commercial paper 6,275 — — 6,275 U.S. government agency securities 4,200 1 — 4,201 Total marketable securities $ 27,754 $ 2 $ (8 ) $ 27,748
Amortized cost and fair value of marketable securities by contractual maturity	As of April 1, 2017 , the amortized cost and fair value of marketable securities by contractual maturity were as follows (in thousands): Amortized Cost Fair Value Due in 1 year or less $ 25,225 $ 25,215

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Apr. 01, 2017
Fair Value Disclosures [Abstract]
Summary of fair values of financial assets	The following table sets forth the Company’s financial assets measured at fair value on a recurring basis as of April 1, 2017 and December 31, 2016 , based on the three-tier fair value hierarchy (in thousands): As of April 1, 2017 Level 1 Level 2 Total Money market funds $ 8,197 $ — $ 8,197 Corporate debt securities — 11,289 11,289 Commercial paper — 10,174 10,174 U.S. government agency securities — 4,198 4,198 Total $ 8,197 $ 25,661 $ 33,858 As of December 31, 2016 Level 1 Level 2 Total Money market funds $ 15,020 $ — $ 15,020 Corporate debt securities — 17,272 17,272 Commercial paper — 7,274 7,274 U.S. government agency securities — 4,201 4,201 Total $ 15,020 $ 28,747 $ 43,767

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	3 Months Ended
	Apr. 01, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of April 1, 2017 and December 31, 2016 are disclosed in the following table (in thousands): April 1, 2017 December 31, 2016 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (68,964 ) $ — $ 68,964 $ (68,151 ) $ 813 Customer relationships 54,740 (54,740 ) — 54,740 (54,740 ) — Total intangible assets, excluding goodwill $ 123,704 $ (123,704 ) $ — $ 123,704 $ (122,891 ) $ 813

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	3 Months Ended
	Apr. 01, 2017
Balance Sheet Related Disclosures [Abstract]
Summary of accounts receivable, net	Accounts receivable, net consisted of the following (in thousands): April 1, December 31, Accounts receivable $ 66,142 $ 52,792 Allowance for doubtful accounts (477 ) (518 ) Product return reserve (1,477 ) (938 ) Accounts receivable, net $ 64,188 $ 51,336
Summary of inventory	Inventory consisted of the following (in thousands): April 1, December 31, Raw materials $ 1,502 $ 1,827 Finished goods 45,036 42,718 Total inventory $ 46,538 $ 44,545
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): April 1, December 31, Test equipment $ 44,466 $ 43,580 Computer equipment and software 31,785 30,306 Furniture and fixtures 2,709 2,831 Leasehold improvements 6,827 6,898 Total 85,787 83,615 Accumulated depreciation and amortization (67,643 ) (65,631 ) Property and equipment, net $ 18,144 $ 17,984
Summary of accrued liabilities	Accrued liabilities consisted of the following (in thousands): April 1, December 31, Advance customer payments $ 22,946 $ 20,726 Accrued compensation and related benefits 22,193 19,541 Accrued warranty and retrofit 10,778 12,214 Accrued professional and consulting fees 9,952 8,205 Accrued excess and obsolete inventory at contract manufacturers 2,415 1,327 Accrued customer rebates 1,425 1,931 Accrued insurance 756 804 Accrued restructuring charges 699 — Income taxes payable 20 231 Accrued other 5,831 4,736 Total accrued liabilities $ 77,015 $ 69,715
Summary of deferred revenue	Deferred revenue consisted of the following (in thousands): April 1, December 31, Current: Product and services $ 41,152 $ 24,472 Extended warranty 3,264 3,382 44,416 27,854 Non-current: Product and services 38 22 Extended warranty 20,838 20,215 20,876 20,237 Total deferred revenue $ 65,292 $ 48,091

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Apr. 01, 2017
Commitments and Contingencies Disclosure [Abstract]
Product warranty activities	Changes in the Company’s warranty and retrofit reserves in the periods as indicated were as follows (in thousands): Three Months Ended April 1, March 26, Balance at beginning of period $ 12,214 $ 9,564 Provision for warranty and retrofit charged to cost of revenue 1,862 580 Utilization of reserve (3,298 ) (619 ) Adjustments to pre-existing reserve — (373 ) Balance at end of period $ 10,778 $ 9,152

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	3 Months Ended
	Apr. 01, 2017
Earnings Per Share [Abstract]
Schedule of net loss per share	The following table sets forth the computation of basic and diluted net loss per common share for the periods indicated (in thousands, except per share data): Three Months Ended April 1, March 26, Numerator: Net loss $ (33,325 ) $ (10,729 ) Denominator: Weighted-average common shares outstanding 49,525 48,591 Basic and diluted net loss per common share $ (0.67 ) $ (0.22 ) Potentially dilutive shares, weighted average 6,145 5,500

Accumulated Other Comprehensi27

Accumulated Other Comprehensive Loss (Tables)	3 Months Ended
	Apr. 01, 2017
Equity [Abstract]
Accumulated other comprehensive income details	The table below summarizes the changes in accumulated other comprehensive loss by component for the periods indicated (in thousands): Three Months Ended April 1, 2017 March 26, 2016 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (6 ) $ (650 ) $ (656 ) $ (94 ) $ (101 ) $ (195 ) Other comprehensive income (loss) (4 ) 61 57 65 (18 ) 47 Balance at end of period $ (10 ) $ (589 ) $ (599 ) $ (29 ) $ (119 ) $ (148 )

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Apr. 01, 2017
Income Tax Disclosure [Abstract]
Schedule of income taxes	The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended April 1, March 26, Provision for income taxes $ 673 $ 121 Effective tax rate (2.1 )% (1.1 )%

Restructuring Charges (Tables)

Restructuring Charges (Tables)	3 Months Ended
	Apr. 01, 2017
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	The following table summarizes the activities related to the restructuring charges pursuant to the above restructuring plan (in thousands): Three Months Ended April 1, 2017 Liability at beginning of period $ — Restructuring charges for the period 699 Cash payments — Liability at end of period $ 699

Significant Accounting Polici30

Significant Accounting Policies (Details)	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Largest Two Customers | Customer Concentration Risk | Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	55.00%	29.00%

Cash, Cash Equivalents and Ma31

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016	Mar. 26, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 26,318	$ 50,359	$ 21,365	$ 23,626
Marketable securities	25,215	27,748
Total cash, cash equivalents and marketable securities	51,533	78,107
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities	10,843	17,272
Commercial paper
Cash and Cash Equivalents [Line Items]
Marketable securities	10,174	6,275
U.S. government agency securities
Cash and Cash Equivalents [Line Items]
Marketable securities	4,198	4,201
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	17,675	34,340
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	8,197	15,020
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	446	0
Commercial paper
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 0	$ 999

Cash, Cash Equivalents and Ma32

Cash, Cash Equivalents and Marketable Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 25,225	$ 27,754
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(10)	(8)
Fair Value	25,215	27,748
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,851	17,279
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(8)	(8)
Fair Value	10,843	17,272
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,174	6,275
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	10,174	6,275
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,200	4,200
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(2)	0
Fair Value	$ 4,198	$ 4,201

Cash, Cash Equivalents and Ma33

Cash, Cash Equivalents and Marketable Securities - Contractual Maturity (Details) $ in Thousands	Apr. 01, 2017USD ($)
Cash and Cash Equivalents [Abstract]
Marketable securities due in 1 year or less, amortized cost	$ 25,225
Marketable securities due in 1 year or less, fair value	$ 25,215

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 25,215	$ 27,748
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	33,858	43,767
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	8,197	15,020
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	25,661	28,747
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,843	17,272
Corporate debt securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	11,289	17,272
Corporate debt securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Corporate debt securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	11,289	17,272
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,174	6,275
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,174	7,274
Commercial paper | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
Commercial paper | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,174	7,274
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,198	4,201
U.S. government agency securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,198	4,201
U.S. government agency securities | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	0
U.S. government agency securities | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	4,198	4,201
Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	8,197	15,020
Money market funds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	8,197	15,020
Money market funds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 0	$ 0

Goodwill and Intangible Asset35

Goodwill and Intangible Assets - Textual (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 813	$ 3,364

Goodwill and Intangible Asset36

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 123,704	$ 123,704
Accumulated Amortization	(123,704)	(122,891)
Net	0	813
Core developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	68,964	68,964
Accumulated Amortization	(68,964)	(68,151)
Net	0	813
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,740	54,740
Accumulated Amortization	(54,740)	(54,740)
Net	$ 0	$ 0

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Summary of accounts receivable, net
Accounts receivable	$ 66,142	$ 52,792
Allowance for doubtful accounts	(477)	(518)
Product return reserve	(1,477)	(938)
Accounts receivable, net	$ 64,188	$ 51,336

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Summary of inventory, net
Raw materials	$ 1,502	$ 1,827
Finished goods	45,036	42,718
Total inventory	$ 46,538	$ 44,545

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Summary of property and equipment, net
Property and equipment, gross	$ 85,787	$ 83,615
Accumulated depreciation and amortization	(67,643)	(65,631)
Property and equipment, net	18,144	17,984
Test equipment
Summary of property and equipment, net
Property and equipment, gross	44,466	43,580
Computer equipment and software
Summary of property and equipment, net
Property and equipment, gross	31,785	30,306
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	2,709	2,831
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	$ 6,827	$ 6,898

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Summary of accrued liabilities
Advance customer payments	$ 22,946	$ 20,726
Accrued compensation and related benefits	22,193	19,541
Accrued warranty and retrofit	10,778	12,214
Accrued professional and consulting fees	9,952	8,205
Accrued excess and obsolete inventory at contract manufacturers	2,415	1,327
Accrued customer rebates	1,425	1,931
Accrued insurance	756	804
Accrued restructuring charges	699	0
Income taxes payable	20	231
Accrued other	5,831	4,736
Total accrued liabilities	$ 77,015	$ 69,715

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Apr. 01, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 44,416	$ 27,854
Deferred revenue, noncurrent	20,876	20,237
Deferred revenue	65,292	48,091
Revenue Contract
Deferred Revenue Arrangement [Line Items]
Deferred revenue	21,500	20,300
Product and services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	41,152	24,472
Deferred revenue, noncurrent	38	22
Extended warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	3,264	3,382
Deferred revenue, noncurrent	$ 20,838	$ 20,215

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details)	3 Months Ended
	Apr. 01, 2017
Commitments and Contingencies [Line Items]
Warranty period	3 years
Minimum
Commitments and Contingencies [Line Items]
Warranty period	1 year
Maximum
Commitments and Contingencies [Line Items]
Warranty period	5 years

Commitments and Contingencies43

Commitments and Contingencies - Product Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Product warranty activities [Roll Forward]
Balance at beginning of period	$ 12,214	$ 9,564
Provision for warranty and retrofit charged to cost of revenue	1,862	580
Utilization of reserve	(3,298)	(619)
Adjustments to pre-existing reserve	0	(373)
Balance at end of period	$ 10,778	$ 9,152

Net Loss per Common Share (Deta

Net Loss per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Numerator:
Net loss	$ (33,325)	$ (10,729)
Denominator:
Weighted-average common shares outstanding (in shares)	49,525	48,591
Basic and diluted net loss per common share (in dollars per share)	$ (0.67)	$ (0.22)
Potentially dilutive shares, weighted average (in shares)	6,145	5,500

Stockholders' Equity - Textual

Stockholders' Equity - Textual (Details) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Apr. 01, 2017USD ($)Plan$ / sharesshares	Mar. 26, 2016USD ($)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | Plan	2
Stock options granted (in shares)	0
Stock options exercised (in shares)	2,000
Weighted-average exercise price per share, stock options (in dollars per share) | $ / shares	$ 6.54
Unrecognized stock-based compensation expense, stock options | $	$ 3,200
Weighted-average amortization period	2 years 9 months 15 days
Taxes paid for awards vested under equity incentive plans | $	$ 1,093	$ 251
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period	2 years 4 months 17 days
Awards granted (in shares)	203,100
Weighted-average grant date fair value per share (in dollars per share) | $ / shares	$ 7
Awards vested (in shares)	52,161
Taxes paid for awards vested under equity incentive plans | $	$ 300
Unrecognized stock-based compensation expense | $	$ 12,600
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period	1 month 15 days
Unrecognized stock-based compensation expense | $	$ 200
ESPP, maximum employee payroll deduction percentage	15.00%
ESPP, maximum number of shares per employee (in shares)	2,000
ESPP, discounted purchase price percentage	85.00%
Offering period	6 months
Shares available for issuance under the ESPP (in shares)	119,228
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period	1 year 4 months 7 days
Awards vested (in shares)	300,000
Shares of stock issued upon conversion of units (in shares)	180,052
Taxes paid for awards vested under equity incentive plans | $	$ 800
Unrecognized stock-based compensation expense | $	$ 700
Period of average closing trading price ending on the last day of applicable performance period					90 days
Period of average closing trading price preceding first day of performance period					90 days
Performance Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	1 year		2 years	2 years	2 years
Target performance rate	0.00%
Performance Restricted Stock Units | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	2 years		3 years	3 years	3 years
Target performance rate	200.00%
Period one - February 2017 | Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	50.00%
Period two - February 2018 | Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%
Period three - February 2019 | Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage	25.00%

Stockholders' Equity - Stock Re

Stockholders' Equity - Stock Repurchase (Details) - Common Stock - USD ($)	11 Months Ended
	Mar. 26, 2016	Apr. 26, 2015
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount		$ 40,000,000
Number of shares repurchased (in shares)	5,329,817
Average price per share (in dollars per share)	$ 7.50

Accumulated Other Comprehensi47

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	$ 212,964
Other comprehensive income (loss)	57	$ 47
Balance at end of period	182,157
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(6)	(94)
Other comprehensive income (loss)	(4)	65
Balance at end of period	(10)	(29)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(650)	(101)
Other comprehensive income (loss)	61	(18)
Balance at end of period	(589)	(119)
Total
Accumulated Other Comprehensive Loss [Roll Forward]
Balance at beginning of period	(656)	(195)
Balance at end of period	$ (599)	$ (148)

Credit Facility (Details)

Credit Facility (Details)	3 Months Ended
	Apr. 01, 2017USD ($)quarterly_payment	Jul. 29, 2013USD ($)
Credit Facility [Line Items]
Maximum borrowing capacity		$ 50,000,000
Interest rate description	Loans under the credit facility bear interest at an annual rate equal to the base rate plus 0.75% to 1.25% or LIBOR plus 2.00% to 2.50% based on a leverage ratio of consolidated funded indebtedness to consolidated Adjusted EBITDA (customarily defined).
Frequency of payment and payment terms	Interest on the revolving facility is due quarterly, and any outstanding interest and principal is due on the maturity date of the revolving facility.
Number of payments to repay principal | quarterly_payment	20
Commitment fee percentage	0.25%
Borrowings under the credit facility	$ 0
Outstanding revolving loans	$ 0
Base Rate | Minimum
Credit Facility [Line Items]
Interest rate margin	0.75%
Base Rate | Maximum
Credit Facility [Line Items]
Interest rate margin	1.25%
LIBOR | Minimum
Credit Facility [Line Items]
Interest rate margin	2.00%
LIBOR | Maximum
Credit Facility [Line Items]
Interest rate margin	2.50%
Letter of Credit
Credit Facility [Line Items]
Maximum borrowing capacity		20,000,000
Swingline Facility
Credit Facility [Line Items]
Maximum borrowing capacity		10,000,000
Repayment period (swingline loans)	10 days
Term Loan
Credit Facility [Line Items]
Maximum borrowing capacity		$ 25,000,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 673	$ 121
Effective tax rate	(2.10%)	(1.10%)

Restructuring Charges (Details)

Restructuring Charges (Details) - USD ($) $ in Thousands	3 Months Ended
	Apr. 01, 2017	Mar. 26, 2016
Restructuring Reserve [Roll Forward]
Restructuring charges for the period	$ 699	$ 0
Expected restructuring charges	6,800
Expected additional charges	6,100
Employee Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	0
Restructuring charges for the period	699
Cash payments	0
Liability at end of period	$ 699