Calix (CALX) 10-Q 2 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 24, 2016	Oct. 24, 2016
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	Sep. 24, 2016
Amendment Flag	false
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		48,789,247

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 31,764	$ 23,626
Marketable securities	29,554	49,964
Accounts receivable, net	57,256	47,155
Inventory	40,190	47,667
Deferred cost of revenue	14,718	4,918
Prepaid expenses and other current assets	15,700	9,470
Total current assets	189,182	182,800
Property and equipment, net	16,017	17,149
Goodwill	116,175	116,175
Intangible assets, net	1,627	6,618
Other assets	937	1,144
Total assets	323,938	323,886
Current liabilities:
Accounts payable	19,340	19,603
Accrued liabilities	49,019	35,512
Deferred revenue	16,226	12,124
Total current liabilities	84,585	67,239
Long-term portion of deferred revenue	19,850	19,569
Other long-term liabilities	979	1,293
Total liabilities	105,414	88,101
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 September 24, 2016 and December 31, 2015	0	0
Common stock, $0.025 par value; 100,000,000 shares authorized; 54,118,410 shares issued and 48,788,593 shares outstanding as of September 24, 2016, and 53,049,781 shares issued and 49,509,251 shares outstanding as of December 31, 2015	1,353	1,326
Additional paid-in capital	830,225	818,754
Accumulated other comprehensive loss	(226)	(195)
Accumulated deficit	(572,842)	(556,923)
Treasury stock, 5,329,817 shares and 3,540,530 shares as of September 24, 2016 and December 31, 2015, respectively	(39,986)	(27,177)
Total stockholders’ equity	218,524	235,785
Total liabilities and stockholders’ equity	$ 323,938	$ 323,886

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 24, 2016	Dec. 31, 2015
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	54,118,410	53,049,781
Common stock, shares outstanding	48,788,593	49,509,251
Treasury stock, shares	5,329,817	3,540,530

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Revenue		$ 121,187	$ 112,297	$ 326,987	$ 302,464
Cost of revenue:
Products and services	[1]	66,830	57,096	174,665	152,308
Amortization of intangible assets		813	2,088	3,290	6,264
Total cost of revenue		67,643	59,184	177,955	158,572
Gross profit		53,544	53,113	149,032	143,892
Operating expenses:
Research and development	[1]	28,119	22,120	75,925	66,885
Sales and marketing	[1]	20,575	18,424	58,850	57,398
General and administrative	[1]	8,615	9,140	32,940	28,728
Amortization of intangible assets		0	2,552	1,701	7,656
Litigation settlement gain		(4,500)	0	(4,500)	0
Total operating expenses		52,809	52,236	164,916	160,667
Income (loss) from operations		735	877	(15,884)	(16,775)
Interest and other income (expense), net:
Interest income		184	297	611	1,014
Interest expense		(155)	(263)	(489)	(921)
Other income (expense), net		81	196	297	273
Income (loss) before provision for income taxes		845	1,107	(15,465)	(16,409)
Provision for income taxes		209	185	454	378
Net income (loss)		$ 636	$ 922	$ (15,919)	$ (16,787)
Net income (loss) per common share:
Earnings per share, basic (in dollars per share)		$ 0.01	$ 0.02	$ (0.33)	$ (0.32)
Earnings per share, diluted (in dollars per share)		$ 0.01	$ 0.02	$ (0.33)	$ (0.32)
Weighted-average number of shares used to compute net loss per common share:
Basic (in shares)		48,773	51,756	48,578	51,814
Diluted (in shares)		49,309	52,016	48,578	51,814
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available-for-sale marketable securities, net		$ (9)	$ 30	$ 97	$ 66
Foreign currency translation adjustments, net		(87)	(196)	(128)	(177)
Total other comprehensive income (loss), net of tax		(96)	(166)	(31)	(111)
Comprehensive income (loss)		540	756	(15,950)	(16,898)
Stock-based compensation		1,700
Cost of revenue
Other comprehensive income (loss), net of tax:
Stock-based compensation		174	163	484	549
Research and development
Other comprehensive income (loss), net of tax:
Stock-based compensation		1,573	964	3,719	3,659
Sales and marketing
Other comprehensive income (loss), net of tax:
Stock-based compensation		1,661	688	3,323	3,769
General and administrative
Other comprehensive income (loss), net of tax:
Stock-based compensation		$ 1,269	$ 775	$ 2,840	$ 2,616
[1]	Includes stock-based compensation as follows: Three and Nine Months Ended September 24, 2016 and September 26, 2015; Cost of revenue - $174, $163, $484, $549; Research and development - $1,573, $964, $3,719, $3,659; Sales and marketing - $1,661, $688, $3,323, $3,769; General administrative - $1,269, $775, $2,840, $2,616;

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015
Operating activities:
Net loss	$ (15,919)	$ (16,787)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	6,282	7,602
Loss on retirement of property and equipment	0	14
Amortization of intangible assets	4,991	13,920
Amortization of premiums related to available-for-sale securities	337	743
Stock-based compensation	10,366	10,593
Changes in operating assets and liabilities:
Restricted cash	0	295
Accounts receivable, net	(10,104)	(17,443)
Inventory	7,477	2,983
Deferred cost of revenue	(9,800)	2,082
Prepaid expenses and other assets	(6,058)	4,181
Accounts payable	(356)	(6,841)
Accrued liabilities	13,974	(1,055)
Deferred revenue	4,383	(1,312)
Other long-term liabilities	(313)	(167)
Net cash provided by (used in) operating activities	5,260	(1,192)
Investing activities:
Purchases of property and equipment	(5,364)	(5,943)
Purchases of marketable securities	0	(46,750)
Maturities of marketable securities	20,170	51,265
Net cash provided by (used in) investing activities	14,806	(1,428)
Financing activities:
Proceeds from exercise of stock options	14	625
Proceeds from employee stock purchase plan	2,905	2,865
Payments for repurchases of common stock	(12,809)	(11,124)
Taxes paid for awards vested under equity incentive plans	(1,787)	(2,093)
Net cash used in financing activities	(11,677)	(9,727)
Effect of exchange rate changes on cash and cash equivalents	(251)	(288)
Net increase (decrease) in cash and cash equivalents	8,138	(12,635)
Cash and cash equivalents at beginning of period	23,626	48,829
Cash and cash equivalents at end of period	$ 31,764	$ 36,194

Company and Basis of Presentati

Company and Basis of Presentation	9 Months Ended
	Sep. 24, 2016
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 systems and software for fiber- and copper-based network architectures that enable communications service providers ("CSPs") to transform their networks and connect to their residential and business subscribers. 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. The Company develops and sells carrier-class hardware and software products, referred to as the Unified Access portfolio, which are designed to enhance and transform CSP access networks to meet the changing demands of subscribers rapidly and cost-effectively. 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, 2015 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 Form 10-K for the year ended December 31, 2015 . 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 one fewer day in the nine months ended September 24, 2016 than in the nine months ended September 26, 2015 . 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.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 24, 2016
Accounting Policies [Abstract]
Significant Accounting Policies	Significant Accounting Policies The Company’s significant accounting policies are disclosed in our Annual Report on Form 10-K for the year ended December 31, 2015 . Our significant accounting policies did not change during the nine months ended September 24, 2016 . Concentration of Customer Risk The Company had two customers that each accounted for more than 10% of its total revenue for the three and nine months ended September 24, 2016 and one of these customers accounted for more than 10% of the Company’s total revenue for the three and nine months ended September 26, 2015 . These two customers together represented 37% and 34% of the Company’s total revenue for the three and nine months ended September 24, 2016 , respectively, and 27% and 26% of the Company’s total revenue for the three and nine months ended September 26, 2015 , respectively. Each of these two customers represented more than 10% of the Company’s accounts receivable as of September 24, 2016 and one of these customers represented more than 10% of the Company’s accounts receivable as of December 31, 2015 . Recent Accounting Pronouncements 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. ASU 2016-09 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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 is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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. ASU 2015-11 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted, and the guidance should be applied prospectively. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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. As a result, the standard will be effective for the Company in the first quarter of fiscal 2018. ASU 2015-14 permits early adoption of the new revenue standard, but not before its original effective date. The Company is currently assessing the method of adoption and the potential impact of adopting this new guidance on its consolidated financial statements.

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 24, 2016
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, U.S. government agency securities and commercial paper. 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, U.S. government agency securities and commercial paper 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 September 24, 2016 and has determined that no investments with unrealized losses are other-than-temporarily impaired. No investments have been in a continuous loss position greater than one year. Cash, cash equivalents and marketable securities consisted of the following (in thousands): September 24, December 31, Cash and cash equivalents: Cash $ 17,708 $ 13,378 Money market funds 14,056 10,248 Total cash and cash equivalents 31,764 23,626 Marketable securities: Corporate debt securities 23,051 35,799 U.S. government agency securities 6,503 10,520 Commercial paper — 3,645 Total marketable securities 29,554 49,964 Total cash, cash equivalents and marketable securities $ 61,318 $ 73,590 The carrying amounts of our money market funds approximate their fair values due to their nature, duration and short maturities. As of September 24, 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 $ 23,050 $ 4 $ (3 ) $ 23,051 U.S. government agency securities 6,501 2 — 6,503 Total marketable securities $ 29,551 $ 6 $ (3 ) $ 29,554 As of December 31, 2015 , 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 $ 35,869 $ 2 $ (72 ) $ 35,799 U.S. government agency securities 10,544 — (24 ) 10,520 Commercial paper 3,645 — — 3,645 Total marketable securities $ 50,058 $ 2 $ (96 ) $ 49,964 As of September 24, 2016 , 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 $ 29,551 $ 29,554

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 24, 2016
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements In accordance with Accounting Standard Codification (“ASC”) Topic 820, Fair Value Measurements and Disclosures , (“ASC Topic 820”), the Company measures its cash equivalents and marketable securities at fair value on a recurring basis. ASC Topic 820 clarifies that 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. As a basis for considering such assumptions, ASC Topic 820 establishes a three-tier value hierarchy, which prioritizes the inputs used in measuring fair value as follows: 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 September 24, 2016 and December 31, 2015 , based on the three-tier fair value hierarchy (in thousands): As of September 24, 2016 Level 1 Level 2 Total Money market funds $ 14,056 $ — $ 14,056 Corporate debt securities — 23,051 23,051 U.S. government agency securities — 6,503 6,503 Total $ 14,056 $ 29,554 $ 43,610 As of December 31, 2015 Level 1 Level 2 Total Money market funds $ 10,248 $ — $ 10,248 Corporate debt securities — 35,799 35,799 U.S. government agency securities — 10,520 10,520 Commercial paper — 3,645 3,645 Total $ 10,248 $ 49,964 $ 60,212 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, U.S. government agency securities and commercial paper 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 nine months ended September 24, 2016 and September 26, 2015 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 24, 2016
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. ("OSI") 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. We evaluate goodwill on an annual basis at the end of the second quarter of each year. Management has determined that we operate 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 September 24, 2016 . Therefore, there was no impairment to the carrying value of the Company's goodwill as of September 24, 2016 . Intangible Assets Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of September 24, 2016 and December 31, 2015 are disclosed in the following table (in thousands): September 24, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (67,337 ) $ 1,627 $ 68,964 $ (64,047 ) $ 4,917 Customer relationships 54,740 (54,740 ) — 54,740 (53,039 ) 1,701 Total intangible assets, excluding goodwill $ 123,704 $ (122,077 ) $ 1,627 $ 123,704 $ (117,086 ) $ 6,618 Amortization expense was $0.8 million and $4.6 million for the three months ended September 24, 2016 and September 26, 2015 , respectively. Amortization expense was $5.0 million and $13.9 million for the nine months ended September 24, 2016 and September 26, 2015 , respectively. As of September 24, 2016 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2016 $ 814 2017 813 Total $ 1,627

Balance Sheet Details

Balance Sheet Details	9 Months Ended
	Sep. 24, 2016
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): September 24, December 31, Accounts receivable $ 58,752 $ 48,319 Allowance for doubtful accounts (629 ) (501 ) Product return reserve (867 ) (663 ) Accounts receivable, net $ 57,256 $ 47,155 Inventory consisted of the following (in thousands): September 24, December 31, Raw materials $ 2,035 $ 2,209 Finished goods 38,155 45,458 Total inventory $ 40,190 $ 47,667 Property and equipment, net consisted of the following (in thousands): September 24, December 31, Test equipment $ 42,038 $ 39,035 Computer equipment and software 29,176 27,736 Furniture and fixtures 2,457 1,833 Leasehold improvements 6,570 6,554 Total 80,241 75,158 Accumulated depreciation and amortization (64,224 ) (58,009 ) Property and equipment, net $ 16,017 $ 17,149 Accrued liabilities consisted of the following (in thousands): September 24, December 31, Accrued compensation and related benefits $ 21,394 $ 13,809 Accrued warranty 11,373 9,564 Accrued professional and consulting fees 5,887 2,813 Accrued customer rebates 2,029 784 Accrued excess and obsolete inventory at contract manufacturers 1,084 1,011 Accrued insurance 946 — Accrued non income related taxes 849 905 Accrued business travel expenses 837 580 Advance customer payments 709 1,094 Accrued rent 412 381 Accrued freight 296 486 Accrued hosting services 248 466 Income taxes payable — 322 Accrued other 2,955 3,297 Total accrued liabilities $ 49,019 $ 35,512 Deferred revenue consisted of the following (in thousands): September 24, December 31, 2015 Current: Product and services $ 12,988 $ 8,937 Extended warranty 3,238 3,187 16,226 12,124 Non-current: Product and services 46 58 Extended warranty 19,804 19,511 19,850 19,569 Total deferred revenue $ 36,076 $ 31,693 Deferred cost of revenue consisted of costs incurred for products and services for which revenues have been deferred.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 24, 2016
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, 2015 are disclosed in our Annual Report on Form 10-K, and have not changed materially during the nine months ended September 24, 2016 . 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 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. The Company accrues for potential warranty claims based on the Company’s historical product failure rates and historical costs incurred in correcting product failures along with other relevant information. The Company's warranty 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 reserve were as follows (in thousands): Three Months Ended Nine Months Ended September 24, September 26, September 24, September 26, Balance at beginning of period $ 9,152 $ 9,325 $ 9,564 $ 9,553 Warranty charged to cost of revenue 3,180 781 6,292 2,929 Utilization of warranty (948 ) (722 ) (4,073 ) (3,098 ) Adjustments to pre-existing warranty (11 ) (400 ) (410 ) (400 ) Balance at end of period $ 11,373 $ 8,984 $ 11,373 $ 8,984 Litigation From time to time, the Company is involved in various legal proceedings arising from the normal course of business activities. Steinhardt v. Howard-Anderson, et al. As previously disclosed, in connection with the Company’s February 22, 2011 merger transaction with Occam Networks, Inc. (“Occam”) a complaint was filed on October 6, 2010 by stockholders of Occam in the Delaware Court of Chancery styled as Steinhardt v. Howard-Anderson, et al. (Case No. 5878-VCL). The complaint, as initially amended, sought injunctive relief rescinding the merger transaction and an award of damages in an unspecified amount, as well as plaintiffs’ costs, attorney’s fees, and other relief, and also alleged that Occam (which has since merged into Calix), each Occam director and the Occam CFO breached their fiduciary duties by failing to attempt to obtain the best purchase price for Occam and failing to disclose certain allegedly material facts about the merger transaction in the preliminary proxy statement and prospectus included in the Registration Statement on Form S-4 for the transaction. In July 2015, the complaint was amended to add Wilson Sonsini Goodrich & Rosati, P.C. (“Wilson Sonsini”), Occam’s counsel and former defense counsel in this lawsuit. Trial on the matter commenced on April 11, 2016 before the Delaware Court of Chancery. On April 14, 2016, the parties entered into a memorandum of understanding of a settlement in principle (“Settlement”) to resolve all of the claims pending before the Delaware Court of Chancery and related claims for a total settlement consideration of $35.0 million . The Settlement was made without any admission of any wrongdoing on the part of the Company or its officers and directors. Further, the Settlement terms provide that neither the Company nor any of its officers or directors would be required to make any contribution to the settlement consideration of $35 million to be paid for the benefit of the plaintiff class. On May 31, 2016, the parties signed a global settlement agreement reflecting the terms of the Settlement and filed the agreement for court approval. The court approved the global settlement at a hearing held on August 26, 2016 and, on September 7, 2016, issued its Order and Final Judgment, terminating the case before the Delaware Court of Chancery. The Company did not previously accrue any estimated loss in connection with this action and, as a result of the Settlement, will not recognize any loss related to this action. The Company incurred defense costs related to this litigation in connection with its obligations, under certain circumstances, to hold harmless and indemnify each of the former Occam directors and officers named as defendants in this action against judgments, fines, settlements and expenses related to claims against such directors and officers to the fullest extent permitted under Delaware law and Occam’s bylaws and certificate of incorporation. In addition, the Company has paid fees and expenses incurred by Jefferies in connection with this matter pursuant to Jefferies indemnity demand under the engagement letter between Occam and Jefferies. Defense costs that were in excess of available insurance coverage or for which the Company’s insurance carriers denied coverage were recorded as operating expense in the Company’s Consolidated Statement of Comprehensive Income (Loss) in the periods incurred. Until the Settlement was reached, the Company continued to incur significant litigation expenses, including expenses that were not covered by insurance, to defend and litigate this matter. For the nine months ended September 24, 2016 , the Company recorded litigation defense costs and expenses in excess of its insurance coverage of $6.4 million as operating expense in the accompanying Condensed Consolidated Statements of Comprehensive Income (Loss). The deadline for appeal of the Order and Final Judgment was October 7, 2016. No appeals were filed and the Company expects to receive the $4.5 million cash payment on or before November 22, 2016. Under the terms of the Settlement (and separate from the settlement consideration), the Company will receive a cash payment of $4.5 million in partial recovery of its out-of-pocket expenses incurred in the litigation, payable to the Company within 45 days of the court’s order entering judgment in the litigation. As disclosed above, the Delaware court issued its Order and Final Judgment on September 7, 2016. Accordingly, during the fiscal quarter ended September 24, 2016 , the Company accrued $4.5 million as “Litigation settlement gain”, presented as a reduction to operating expenses in the accompanying Condensed Consolidated Statements of Comprehensive Income (Loss). The Company is not currently a party to any other legal proceedings that, if determined adversely to the Company, in management’s opinion, is 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 Income (Loss) per Common Sh

Net Income (Loss) per Common Share	9 Months Ended
	Sep. 24, 2016
Earnings Per Share [Abstract]
Net Income (Loss) per Common Share	Net Income (Loss) per Common Share The following table sets forth the computation of basic and diluted net income (loss) per common share for the periods indicated (in thousands, except per share data): Three Months Ended Nine Months Ended September 24, September 26, September 24, September 26, Numerator: Net income (loss) $ 636 $ 922 $ (15,919 ) $ (16,787 ) Denominator: Weighted-average common shares outstanding used to compute basic net income (loss) per share 48,773 51,756 48,578 51,814 Effect of dilutive common stock equivalents 536 260 — — Weighted-average common shares outstanding used to compute diluted net income (loss) per share 49,309 52,016 48,578 51,814 Basic net income (loss) per common share $ 0.01 $ 0.02 $ (0.33 ) $ (0.32 ) Diluted net income (loss) per common share $ 0.01 $ 0.02 $ (0.33 ) $ (0.32 ) Potentially dilutive shares, weighted average 3,951 5,244 5,794 6,062 For the three and nine months ended September 26, 2015, unvested restricted stock awards are included in the calculation of weighted-average common shares outstanding because such shares are participating securities; however, the impact was immaterial. All restricted stock awards completed their vesting on July 20, 2015. 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 awards. For 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	9 Months Ended
	Sep. 24, 2016
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 Form 10-K filed with the SEC on February 26, 2016 . 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"), restricted stock awards ("RSAs"), and performance restricted stock units ("PRSUs"). Stock Options During the three and nine months ended September 24, 2016 , the Company granted 380,000 stock options at a weighted-average grant date fair value of $3.29 per share as determined using the Black-Scholes option-pricing model . During the three months ended September 24, 2016 , no stock options were exercised. During the nine months ended September 24, 2016 , 2,312 stock options were exercised at a weighted-average exercise price of $5.85 per share. As of September 24, 2016 , unrecognized stock-based compensation expense of $3.1 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.6 years. Restricted Stock Units During the three months ended September 24, 2016 , 102,200 RSUs were granted with a weighted-average grant date fair value of $7.84 per share. During the nine months ended September 24, 2016 , 1,094,513 RSUs were granted with a weighted-average grant date fair value of $7.01 per share. During the three months ended September 24, 2016 , 58,444 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 $0.2 million were remitted to the relevant taxing authorities during the three months ended September 24, 2016 . During the nine months ended September 24, 2016 , 546,534 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 $1.7 million were remitted to the relevant taxing authorities during the nine months ended September 24, 2016 . As of September 24, 2016 , unrecognized stock-based compensation expense of $14.6 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 2.6 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. During the three months ended September 24, 2016 , no PRSUs were granted to executives. During the nine months ended September 24, 2016 , the Company granted 550,000 PRSUs to its executives with a weighted-average grant date fair value of $7.42 per share. These particular performance-based awards contain a one -year performance period and a subsequent two -year service period. The performance target 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, each PRSU award shall vest in 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 September 24, 2016 , no PRSUs vested and were converted into shares of common stock. During the nine months ended September 24, 2016 , 44,992 PRSUs vested and were converted into 26,557 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 $0.1 million were remitted to the relevant taxing authorities during the nine months ended September 24, 2016 . As of September 24, 2016 , unrecognized stock-based compensation expense of $2.2 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 1.1 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 are 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 commencing 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 plan 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 September 24, 2016 , there were 635,913 shares available for issuance under the ESPP. During the three and nine months ended September 24, 2016 , 493,226 shares were purchased under the ESPP. As of September 24, 2016 , 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 month . Stock-Based Compensation Expense Stock-based compensation expense associated with stock options, RSUs, PRSUs, RSAs, 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 and RSAs 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. The probability of meeting the performance condition related to PRSUs granted to executives in February 2016 was assessed to be unlikely in prior quarters, as such, no stock-based compensation expense was recognized for this award in prior quarters. Based on the most recent assessment made by the Company as of September 24, 2016 , the performance condition is now determined to be probable of being met. Accordingly, the corresponding stock-based compensation expense from the grant date to September 24, 2016 of $1.7 million was recorded during the quarter ended September 24, 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. Stock may be purchased under this program 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"). Any open market purchases will 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) will be made at management’s discretion at prices management considers to be attractive and in the best interests of the Company and its stockholders. The stock repurchase commenced in May 2015 and the program was completed in March 2016. During the nine months ended September 24, 2016 , the Company repurchased 1,789,287 shares of common stock for $12.8 million at an average price of $7.16 per share. The Company has 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 Income (Loss)	9 Months Ended
	Sep. 24, 2016
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands). Three Months Ended September 24, 2016 September 26, 2015 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 $ 12 $ (142 ) $ (130 ) $ (22 ) $ 157 $ 135 Other comprehensive income (loss) (9 ) (87 ) (96 ) 30 (196 ) (166 ) Balance at end of period $ 3 $ (229 ) $ (226 ) $ 8 $ (39 ) $ (31 ) Nine Months Ended September 24, 2016 September 26, 2015 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 $ (94 ) $ (101 ) $ (195 ) $ (58 ) $ 138 $ 80 Other comprehensive income (loss) 97 (128 ) (31 ) 66 (177 ) (111 ) Balance at end of period $ 3 $ (229 ) $ (226 ) $ 8 $ (39 ) $ (31 ) Realized gains and losses on sales of available-for-sale marketable securities, if any, are reclassified from accumulated other comprehensive income (loss) to "Other income (expense)" in the accompanying Condensed Consolidated Statements of Comprehensive Income (Loss).

Credit Facility

Credit Facility	9 Months Ended
	Sep. 24, 2016
Line of Credit Facility [Abstract]
Credit Facility	Credit Facility The Company had a revolving credit facility ("Prior Credit Facility") of $30.0 million with Silicon Valley Bank based upon a percentage of eligible accounts receivable, which matured on June 30, 2013 . After the Prior Credit Facility matured on June 30, 2013, the Company cash collateralized any outstanding letters of credit with Silicon Valley Bank. During the first quarter of 2015, Silicon Valley Bank subsequently released the $0.3 million cash restricted for collateralizing the outstanding letters of credit reported as "restricted cash" in the Company's Consolidated Balance Sheet as of December 31, 2014. 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 facility includes affirmative and negative covenants applicable to the Company that are typical for credit facilities of this type. Furthermore, the Credit Agreement requires us 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 September 24, 2016 , the Company was in compliance with these requirements. The credit facility 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 September 24, 2016 , no revolving loans were drawn under the Credit Agreement, as amended. The Company incurred debt issuance costs that were directly attributable to the original issuance and amendment of this credit facility of $0.3 million in 2013 and $0.1 million in 2015, respectively. These costs are amortized over the extended term of the credit facility. As of September 24, 2016 , the unamortized balance of debt issuance costs were $145.1 thousand , of which $72.6 thousand were included within "Prepaid expenses and other current assets" and $72.6 thousand were included within "Other assets" in the Company's Condensed Consolidated Balance Sheets.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 24, 2016
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 Nine Months Ended September 24, September 26, September 24, September 26, Provision for income taxes $ 209 $ 185 $ 454 $ 378 Effective tax rate 24.7 % 16.7 % (2.9 )% (2.3 )% The income tax provision for the three and nine months ended September 24, 2016 and September 26, 2015 consisted primarily of foreign income taxes. The effective tax rate for the three and nine months ended September 24, 2016 and September 26, 2015 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 and nine months ended September 24, 2016 and September 26, 2015 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 . Our 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 we operate, 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 we conduct business .

Significant Accounting Polici18

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 24, 2016
Accounting Policies [Abstract]
Recent Accounting Pronouncements	Recent Accounting Pronouncements 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. ASU 2016-09 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted in any interim or annual period, with any adjustments reflected as of the beginning of the fiscal year of adoption. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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 is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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. ASU 2015-11 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted, and the guidance should be applied prospectively. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. 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. As a result, the standard will be effective for the Company in the first quarter of fiscal 2018. ASU 2015-14 permits early adoption of the new revenue standard, but not before its original effective date. The Company is currently assessing the method of adoption and the potential impact of adopting this new guidance on its consolidated financial statements.

Cash, Cash Equivalents and Ma19

Cash, Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 24, 2016
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash, cash equivalents and marketable securities consisted of the following (in thousands): September 24, December 31, Cash and cash equivalents: Cash $ 17,708 $ 13,378 Money market funds 14,056 10,248 Total cash and cash equivalents 31,764 23,626 Marketable securities: Corporate debt securities 23,051 35,799 U.S. government agency securities 6,503 10,520 Commercial paper — 3,645 Total marketable securities 29,554 49,964 Total cash, cash equivalents and marketable securities $ 61,318 $ 73,590
Amortized cost and fair value of marketable securities	As of September 24, 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 $ 23,050 $ 4 $ (3 ) $ 23,051 U.S. government agency securities 6,501 2 — 6,503 Total marketable securities $ 29,551 $ 6 $ (3 ) $ 29,554 As of December 31, 2015 , 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 $ 35,869 $ 2 $ (72 ) $ 35,799 U.S. government agency securities 10,544 — (24 ) 10,520 Commercial paper 3,645 — — 3,645 Total marketable securities $ 50,058 $ 2 $ (96 ) $ 49,964
Amortized cost and fair value of marketable securities by contractual maturity	As of September 24, 2016 , 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 $ 29,551 $ 29,554

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 24, 2016
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 September 24, 2016 and December 31, 2015 , based on the three-tier fair value hierarchy (in thousands): As of September 24, 2016 Level 1 Level 2 Total Money market funds $ 14,056 $ — $ 14,056 Corporate debt securities — 23,051 23,051 U.S. government agency securities — 6,503 6,503 Total $ 14,056 $ 29,554 $ 43,610 As of December 31, 2015 Level 1 Level 2 Total Money market funds $ 10,248 $ — $ 10,248 Corporate debt securities — 35,799 35,799 U.S. government agency securities — 10,520 10,520 Commercial paper — 3,645 3,645 Total $ 10,248 $ 49,964 $ 60,212

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 24, 2016
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 September 24, 2016 and December 31, 2015 are disclosed in the following table (in thousands): September 24, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (67,337 ) $ 1,627 $ 68,964 $ (64,047 ) $ 4,917 Customer relationships 54,740 (54,740 ) — 54,740 (53,039 ) 1,701 Total intangible assets, excluding goodwill $ 123,704 $ (122,077 ) $ 1,627 $ 123,704 $ (117,086 ) $ 6,618
Expected future amortization	As of September 24, 2016 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2016 $ 814 2017 813 Total $ 1,627

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 24, 2016
Balance Sheet Related Disclosures [Abstract]
Summary of accounts receivable, net	Accounts receivable, net consisted of the following (in thousands): September 24, December 31, Accounts receivable $ 58,752 $ 48,319 Allowance for doubtful accounts (629 ) (501 ) Product return reserve (867 ) (663 ) Accounts receivable, net $ 57,256 $ 47,155
Summary of inventory	Inventory consisted of the following (in thousands): September 24, December 31, Raw materials $ 2,035 $ 2,209 Finished goods 38,155 45,458 Total inventory $ 40,190 $ 47,667
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): September 24, December 31, Test equipment $ 42,038 $ 39,035 Computer equipment and software 29,176 27,736 Furniture and fixtures 2,457 1,833 Leasehold improvements 6,570 6,554 Total 80,241 75,158 Accumulated depreciation and amortization (64,224 ) (58,009 ) Property and equipment, net $ 16,017 $ 17,149
Summary of accrued liabilities	Accrued liabilities consisted of the following (in thousands): September 24, December 31, Accrued compensation and related benefits $ 21,394 $ 13,809 Accrued warranty 11,373 9,564 Accrued professional and consulting fees 5,887 2,813 Accrued customer rebates 2,029 784 Accrued excess and obsolete inventory at contract manufacturers 1,084 1,011 Accrued insurance 946 — Accrued non income related taxes 849 905 Accrued business travel expenses 837 580 Advance customer payments 709 1,094 Accrued rent 412 381 Accrued freight 296 486 Accrued hosting services 248 466 Income taxes payable — 322 Accrued other 2,955 3,297 Total accrued liabilities $ 49,019 $ 35,512
Summary of deferred revenue	Deferred revenue consisted of the following (in thousands): September 24, December 31, 2015 Current: Product and services $ 12,988 $ 8,937 Extended warranty 3,238 3,187 16,226 12,124 Non-current: Product and services 46 58 Extended warranty 19,804 19,511 19,850 19,569 Total deferred revenue $ 36,076 $ 31,693

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 24, 2016
Commitments and Contingencies Disclosure [Abstract]
Product warranty activities	Changes in the Company’s warranty reserve were as follows (in thousands): Three Months Ended Nine Months Ended September 24, September 26, September 24, September 26, Balance at beginning of period $ 9,152 $ 9,325 $ 9,564 $ 9,553 Warranty charged to cost of revenue 3,180 781 6,292 2,929 Utilization of warranty (948 ) (722 ) (4,073 ) (3,098 ) Adjustments to pre-existing warranty (11 ) (400 ) (410 ) (400 ) Balance at end of period $ 11,373 $ 8,984 $ 11,373 $ 8,984

Net Income (Loss) per Common 24

Net Income (Loss) per Common Share (Tables)	9 Months Ended
	Sep. 24, 2016
Earnings Per Share [Abstract]
Schedule of net loss per share	The following table sets forth the computation of basic and diluted net income (loss) per common share for the periods indicated (in thousands, except per share data): Three Months Ended Nine Months Ended September 24, September 26, September 24, September 26, Numerator: Net income (loss) $ 636 $ 922 $ (15,919 ) $ (16,787 ) Denominator: Weighted-average common shares outstanding used to compute basic net income (loss) per share 48,773 51,756 48,578 51,814 Effect of dilutive common stock equivalents 536 260 — — Weighted-average common shares outstanding used to compute diluted net income (loss) per share 49,309 52,016 48,578 51,814 Basic net income (loss) per common share $ 0.01 $ 0.02 $ (0.33 ) $ (0.32 ) Diluted net income (loss) per common share $ 0.01 $ 0.02 $ (0.33 ) $ (0.32 ) Potentially dilutive shares, weighted average 3,951 5,244 5,794 6,062

Accumulated Other Comprehensi25

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 24, 2016
Equity [Abstract]
Accumulated other comprehensive income details	The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands). Three Months Ended September 24, 2016 September 26, 2015 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 $ 12 $ (142 ) $ (130 ) $ (22 ) $ 157 $ 135 Other comprehensive income (loss) (9 ) (87 ) (96 ) 30 (196 ) (166 ) Balance at end of period $ 3 $ (229 ) $ (226 ) $ 8 $ (39 ) $ (31 ) Nine Months Ended September 24, 2016 September 26, 2015 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 $ (94 ) $ (101 ) $ (195 ) $ (58 ) $ 138 $ 80 Other comprehensive income (loss) 97 (128 ) (31 ) 66 (177 ) (111 ) Balance at end of period $ 3 $ (229 ) $ (226 ) $ 8 $ (39 ) $ (31 )

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 24, 2016
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 Nine Months Ended September 24, September 26, September 24, September 26, Provision for income taxes $ 209 $ 185 $ 454 $ 378 Effective tax rate 24.7 % 16.7 % (2.9 )% (2.3 )%

Significant Accounting Polici27

Significant Accounting Policies (Details) - Customer Concentration Risk - customer	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Revenue
Concentration Risk [Line Items]
Number of major customers	2	1	2	1
Accounts Receivable
Concentration Risk [Line Items]
Number of major customers			2
Largest Two Customers | Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	37.00%	27.00%	34.00%	26.00%

Cash, Cash Equivalents and Ma28

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015	Sep. 26, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 31,764	$ 23,626	$ 36,194	$ 48,829
Marketable securities	29,554	49,964
Total cash, cash equivalents and marketable securities	61,318	73,590
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities	23,051	35,799
U.S. government agency securities
Cash and Cash Equivalents [Line Items]
Marketable securities	6,503	10,520
Commercial paper
Cash and Cash Equivalents [Line Items]
Marketable securities	0	3,645
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	17,708	13,378
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 14,056	$ 10,248

Cash, Cash Equivalents and Ma29

Cash, Cash Equivalents and Marketable Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 29,551	$ 50,058
Gross Unrealized Gains	6	2
Gross Unrealized Losses	(3)	(96)
Fair Value	29,554	49,964
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,050	35,869
Gross Unrealized Gains	4	2
Gross Unrealized Losses	(3)	(72)
Fair Value	23,051	35,799
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,501	10,544
Gross Unrealized Gains	2	0
Gross Unrealized Losses	0	(24)
Fair Value	6,503	10,520
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		3,645
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value	$ 0	$ 3,645

Cash, Cash Equivalents and Ma30

Cash, Cash Equivalents and Marketable Securities - Contractual Maturity (Details) $ in Thousands	Sep. 24, 2016USD ($)
Cash and Cash Equivalents [Abstract]
Marketable securities due in 1 year or less, amortized cost	$ 29,551
Marketable securities due in 1 year or less, fair value	$ 29,554

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 29,554	$ 49,964
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	43,610	60,212
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	14,056	10,248
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	29,554	49,964
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	23,051	35,799
Corporate debt securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	23,051	35,799
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	23,051	35,799
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	6,503	10,520
U.S. government agency securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	6,503	10,520
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	6,503	10,520
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	0	3,645
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,645
Commercial paper | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		0
Commercial paper | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities		3,645
Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	14,056	10,248
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	14,056	10,248
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 Asset32

Goodwill and Intangible Assets - Textual (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 800	$ 4,600	$ 4,991	$ 13,920

Goodwill and Intangible Asset33

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 123,704	$ 123,704
Accumulated Amortization	(122,077)	(117,086)
Net	1,627	6,618
Core developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	68,964	68,964
Accumulated Amortization	(67,337)	(64,047)
Net	1,627	4,917
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,740	54,740
Accumulated Amortization	(54,740)	(53,039)
Net	$ 0	$ 1,701

Goodwill and Intangible Asset34

Goodwill and Intangible Assets - Expected Future Amortization (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Expected future amortization
Remainder of 2016	$ 814
2,017	813
Net	$ 1,627	$ 6,618

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Summary of accounts receivable, net
Accounts receivable	$ 58,752	$ 48,319
Allowance for doubtful accounts	(629)	(501)
Product return reserve	(867)	(663)
Accounts receivable, net	$ 57,256	$ 47,155

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Summary of inventory, net
Raw materials	$ 2,035	$ 2,209
Finished goods	38,155	45,458
Total inventory	$ 40,190	$ 47,667

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Summary of property and equipment, net
Property and equipment, gross	$ 80,241	$ 75,158
Accumulated depreciation and amortization	(64,224)	(58,009)
Property and equipment, net	16,017	17,149
Test equipment
Summary of property and equipment, net
Property and equipment, gross	42,038	39,035
Computer equipment and software
Summary of property and equipment, net
Property and equipment, gross	29,176	27,736
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	2,457	1,833
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	$ 6,570	$ 6,554

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Summary of accrued liabilities
Accrued compensation and related benefits	$ 21,394	$ 13,809
Accrued warranty	11,373	9,564
Accrued professional and consulting fees	5,887	2,813
Accrued customer rebates	2,029	784
Accrued excess and obsolete inventory at contract manufacturers	1,084	1,011
Accrued insurance	946	0
Accrued non income related taxes	849	905
Accrued business travel expenses	837	580
Advance customer payments	709	1,094
Accrued rent	412	381
Accrued freight	296	486
Accrued hosting services	248	466
Income taxes payable	0	322
Accrued other	2,955	3,297
Total accrued liabilities	$ 49,019	$ 35,512

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 24, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 16,226	$ 12,124
Deferred revenue, noncurrent	19,850	19,569
Deferred revenue	36,076	31,693
Product and services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	12,988	8,937
Deferred revenue, noncurrent	19,804	19,511
Extended warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	3,238	3,187
Deferred revenue, noncurrent	$ 46	$ 58

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details) - USD ($) $ in Thousands	Apr. 14, 2016	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Commitments and Contingencies [Line Items]
Warranty period				3 years
Litigation settlement gain		$ 4,500	$ 0	$ 4,500	$ 0
Minimum
Commitments and Contingencies [Line Items]
Warranty period				1 year
Maximum
Commitments and Contingencies [Line Items]
Warranty period				5 years
Pending Litigation | Chen v. Howard-Anderson, et al.
Commitments and Contingencies [Line Items]
Settlement consideration to be paid, if settlement becomes final	$ 35,000
Legal fees				$ 6,400
Recovery of settlement costs	$ 4,500
Number of days for settlement after court's judgment				45 days
Litigation settlement gain		$ 4,500

Commitments and Contingencies41

Commitments and Contingencies - Product Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Product warranty activities [Roll Forward]
Balance at beginning of period	$ 9,152	$ 9,325	$ 9,564	$ 9,553
Warranty charged to cost of revenue	3,180	781	6,292	2,929
Utilization of warranty	(948)	(722)	(4,073)	(3,098)
Adjustments to pre-existing warranty	(11)	(400)	(410)	(400)
Balance at end of period	$ 11,373	$ 8,984	$ 11,373	$ 8,984

Net Income (Loss) per Common 42

Net Income (Loss) per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Numerator:
Net income (loss)	$ 636	$ 922	$ (15,919)	$ (16,787)
Denominator:
Weighted-average common shares outstanding used to compute basic net income (loss) per share (in shares)	48,773	51,756	48,578	51,814
Effect of dilutive common stock equivalents (in shares)	536	260	0	0
Weighted-average common shares outstanding used to compute diluted net income (loss) per share (in shares)	49,309	52,016	48,578	51,814
Basic net income (loss) per common share (in dollars per share)	$ 0.01	$ 0.02	$ (0.33)	$ (0.32)
Diluted net income (loss) per common share (in dollars per share)	$ 0.01	$ 0.02	$ (0.33)	$ (0.32)
Potentially dilutive shares, weighted average (in shares)	3,951	5,244	5,794	6,062

Stockholders' Equity - Textual

Stockholders' Equity - Textual (Details) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 24, 2016USD ($)Plan$ / sharesshares	Sep. 24, 2016USD ($)Plan$ / sharesshares	Sep. 26, 2015USD ($)shares	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	2
Stock options granted (in shares)	380,000	380,000
Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 3.29	$ 3.29
Stock options exercised (in shares)	0	2,312
Weighted-average exercise price per share, stock options (in dollars per share) | $ / shares		$ 5.85
Unrecognized stock-based compensation expense, stock options | $	$ 3,100	$ 3,100
Weighted-average amortization period		2 years 6 months 26 days
Taxes paid for awards vested under equity incentive plans | $		$ 1,787	$ 2,093
Stock-based compensation | $	$ 1,700
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period		2 years 7 months 6 days
Awards granted (in shares)	102,200	1,094,513
Weighted-average grant date fair value per share (in dollars per share) | $ / shares	$ 7.84	$ 7.01
Awards vested (in shares)	58,444	546,534
Taxes paid for awards vested under equity incentive plans | $	$ 200	$ 1,700
Unrecognized stock-based compensation expense | $	14,600	$ 14,600
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period		1 month
Unrecognized stock-based compensation expense | $	$ 200	$ 200
ESPP, maximum employee payroll deduction percentage	15.00%	15.00%
ESPP, maximum number of shares per employee (in shares)		2,000
ESPP, discounted purchase price percentage		85.00%
Shares available for issuance under the ESPP (in shares)	635,913	635,913
Shares issued under the ESPP (in shares)	493,226		493,226
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period		1 year 1 month 14 days
Awards granted (in shares)	0	550,000
Weighted-average grant date fair value per share (in dollars per share) | $ / shares		$ 7.42
Taxes paid for awards vested under equity incentive plans | $		$ 100
Unrecognized stock-based compensation expense | $	$ 2,200	$ 2,200
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
Shares converted into common stock (in shares)		44,992
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%
Common Stock | Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of stock issued upon conversion of units (in shares)		26,557
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 ($)	9 Months Ended	11 Months Ended
	Sep. 24, 2016	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)	1,789,287	5,329,817
Shares repurchased, value	$ 12,800,000
Average price per share (in dollars per share)	$ 7.16	$ 7.50

Accumulated Other Comprehensi45

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period			$ 235,785
Balance at end of period	$ 218,524		218,524
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	12	$ (22)	(94)	$ (58)
Other comprehensive income (loss)	(9)	30	97	66
Balance at end of period	3	8	3	8
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(142)	157	(101)	138
Other comprehensive income (loss)	(87)	(196)	(128)	(177)
Balance at end of period	(229)	(39)	(229)	(39)
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(130)	135	(195)	80
Other comprehensive income (loss)	(96)	(166)	(31)	(111)
Balance at end of period	$ (226)	$ (31)	$ (226)	$ (31)

Credit Facility (Details)

Credit Facility (Details)	Jul. 29, 2013USD ($)	Jun. 30, 2013USD ($)	Mar. 28, 2015USD ($)	Sep. 24, 2016USD ($)quarterly_payment	Sep. 26, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)
Credit Facility [Line Items]
Maximum borrowing capacity	$ 50,000,000
Maturity date	Sep. 30, 2018
Restricted cash released			$ (300,000)	$ 0	$ (295,000)
Initiation date	Jul. 29, 2013
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%
Outstanding revolving loans				$ 0
Borrowings under the credit facility				0
Debt issuance costs paid						$ 100,000	$ 300,000
Unamortized debt issuance costs				145,100
Prepaid Expenses and Other Current Assets
Credit Facility [Line Items]
Unamortized debt issuance costs				72,600
Other Assets
Credit Facility [Line Items]
Unamortized debt issuance costs				$ 72,600
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%
Prior Credit Facility
Credit Facility [Line Items]
Maximum borrowing capacity		$ 30,000,000
Maturity date		Jun. 30, 2013
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		9 Months Ended
	Sep. 24, 2016	Sep. 26, 2015	Sep. 24, 2016	Sep. 26, 2015
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 209	$ 185	$ 454	$ 378
Effective tax rate	24.70%	16.70%	(2.90%)	(2.30%)