Calix (CALX) 10-Q 4 May 16 2016 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 26, 2016	Apr. 25, 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	Mar. 26, 2016
Amendment Flag	false
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		47,924,395

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 21,365	$ 23,626
Marketable securities	42,895	49,964
Accounts receivable, net	43,804	47,155
Inventory	41,127	47,667
Deferred cost of revenue	4,108	4,918
Prepaid expenses and other current assets	9,972	9,470
Total current assets	163,271	182,800
Property and equipment, net	16,515	17,149
Goodwill	116,175	116,175
Intangible assets, net	3,254	6,618
Other assets	1,202	1,144
Total assets	300,417	323,886
Current liabilities:
Accounts payable	11,144	19,603
Accrued liabilities	43,801	35,512
Deferred revenue	9,802	12,124
Total current liabilities	64,747	67,239
Long-term portion of deferred revenue	19,696	19,569
Other long-term liabilities	1,196	1,293
Total liabilities	$ 85,639	$ 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 March 26, 2016 and December 31, 2015	$ 0	$ 0
Common stock, $0.025 par value; 100,000,000 shares authorized; 53,110,593 shares issued and 47,780,776 shares outstanding as of March 26, 2016, and 53,049,781 shares issued and 49,509,251 shares outstanding as of December 31, 2015	1,328	1,326
Additional paid-in capital	821,236	818,754
Accumulated other comprehensive loss	(148)	(195)
Accumulated deficit	(567,652)	(556,923)
Treasury stock, 5,329,817 shares and 3,540,530 shares as of March 26, 2016 and December 31, 2015, respectively	(39,986)	(27,177)
Total stockholders’ equity	214,778	235,785
Total liabilities and stockholders’ equity	$ 300,417	$ 323,886

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 26, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 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	$ 0.025	$ 0.025
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	53,110,593	53,049,781
Common stock, shares outstanding	47,780,776	49,509,251
Treasury stock, shares	5,329,817	3,540,530

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended
		Mar. 26, 2016	Mar. 28, 2015
Revenue		$ 98,375	$ 91,038
Cost of revenue:
Products and services	[1]	51,230	46,460
Amortization of intangible assets		1,663	2,088
Total cost of revenue		52,893	48,548
Gross profit		45,482	42,490
Operating expenses:
Research and development	[1]	22,773	21,914
Sales and marketing	[1]	19,062	19,759
General and administrative	[1]	12,684	10,152
Amortization of intangible assets		1,701	2,552
Total operating expenses		56,220	54,377
Loss from operations		(10,738)	(11,887)
Interest and other income (expense), net:
Interest income		211	379
Interest expense		(164)	(379)
Other income (expense), net		83	48
Loss before provision for income taxes		(10,608)	(11,839)
Provision for income taxes		121	91
Net loss		$ (10,729)	$ (11,930)
Net loss per common share:
Basic and diluted (in dollars per share)		$ (0.22)	$ (0.23)
Weighted-average number of shares used to compute net loss per common share:
Basic and diluted (in shares)		48,591	51,732
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available-for-sale marketable securities, net		$ 65	$ 39
Foreign currency translation adjustments, net		(18)	(30)
Total other comprehensive income (loss), net of tax		47	9
Comprehensive loss		(10,682)	(11,921)
Cost of revenue
Other comprehensive income (loss), net of tax:
Stock-based compensation		127	175
Research and development
Other comprehensive income (loss), net of tax:
Stock-based compensation		1,047	1,212
Sales and marketing
Other comprehensive income (loss), net of tax:
Stock-based compensation		822	1,425
General and administrative
Other comprehensive income (loss), net of tax:
Stock-based compensation		$ 725	$ 850
[1]	Includes stock-based compensation as follows: Three Months Ended March 26, 2016 and March 28, 2015; Cost of revenue - $127, $175; Research and development - $1,047, $1,212; Sales and marketing - $822, $1,425; General administrative - $725, $850; Total - $2,721, $3,662

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Operating activities:
Net loss	$ (10,729)	$ (11,930)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	1,955	2,480
Loss on retirement of property and equipment	0	10
Amortization of intangible assets	3,364	4,640
Amortization of premiums related to available-for-sale securities	114	287
Stock-based compensation	2,721	3,662
Changes in operating assets and liabilities:
Restricted cash	0	295
Accounts receivable, net	3,351	(8,256)
Inventory	6,540	6,115
Deferred cost of revenue	810	3,318
Prepaid expenses and other assets	(576)	1,974
Accounts payable	(8,459)	(10,836)
Accrued liabilities	8,471	54
Deferred revenue	(2,195)	(3,651)
Other long-term liabilities	(98)	(59)
Net cash provided by (used in) operating activities	5,269	(11,897)
Investing activities:
Purchases of property and equipment	(1,453)	(1,742)
Purchases of marketable securities	0	(17,004)
Maturities of marketable securities	7,020	11,450
Net cash provided by (used in) investing activities	5,567	(7,296)
Financing activities:
Proceeds from exercise of stock options	14	564
Payments for repurchases of common stock	(12,809)	0
Taxes paid for awards vested under equity incentive plans	(251)	(506)
Net cash provided by (used in) financing activities	(13,046)	58
Effect of exchange rate changes on cash and cash equivalents	(51)	(76)
Net decrease in cash and cash equivalents	(2,261)	(19,211)
Cash and cash equivalents at beginning of period	23,626	48,829
Cash and cash equivalents at end of period	$ 21,365	$ 29,618

Company and Basis of Presentati

Company and Basis of Presentation	3 Months Ended
	Mar. 26, 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 three months ended March 26, 2016 than in the three months ended March 28, 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	3 Months Ended
	Mar. 26, 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 three months ended March 26, 2016 . 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 March 26, 2016 and one of these customers accounted for more than 10% of the Company’s total revenue for the three months ended March 28, 2015. These two customers represented 29% and 26% of the Company’s total revenue for the three months ended March 26, 2016 and March 28, 2015, respectively, and one of these customers represented 10% of the Company’s accounts receivable as of March 26, 2016. 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 includes provisions intended to simplify the following aspects related to how share-based payments are accounted for and presented in the financial statements: a. Accounting for Income Taxes: ASU 2016-09 requires recognition of all of the tax effects related to share-based payments at settlement (or expiration) through the statement of operations. Under the current GAAP, tax benefits in excess of compensation cost (“windfalls”) are recorded in equity, and tax deficiencies (“shortfalls”) are recorded in equity to the extent of previous windfalls, and then to the statement of operations. ASU 2016-09 is required to be applied prospectively to all excess tax benefits and tax deficiencies resulting from settlements after the date of adoption. ASU 2016-09 also removes the requirement to delay recognition of a windfall tax benefit until it reduces current taxes payable. Under the new guidance, the benefit will be recorded when it arises, subject to normal valuation allowance considerations. This change is required to be applied on a modified retrospective basis, with a cumulative-effect adjustment to opening retained earnings. 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. Either prospective or retrospective transition of this change in cash flow presentation is permitted. c. Forfeitures: ASU 2016-09 allows companies to make an accounting policy election to either estimate the number of awards that are expected to vest (current GAAP) or account for forfeitures when they occur. Estimates of forfeitures will still be required in certain circumstances, such as at the time of modification of an award or issuance of a replacement award in a business combination. If elected, the change to recognize forfeitures when they occur needs to be adopted using a modified retrospective approach, with a cumulative effect adjustment recorded to opening retained earnings. d. Minimum Statutory Tax Withholding Requirements: ASU 2016-09 allows companies to withhold an amount up to the employees’ maximum individual tax rate in the relevant jurisdiction without resulting in liability classification of the award. This provision is required to be adopted using a modified retrospective approach, with a cumulative-effect adjustment to opening retained earnings for any outstanding liability awards that qualify for equity classification under the ASU. 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. This change should be applied retrospectively. 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 increases transparency and comparability among companies by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. ASU 2016-02 requires a lessee to recognize in its balance sheet a liability to make lease payments (the lease liability) and a right-to-use asset representing its right to use the underlying asset for the lease term. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from current GAAP. ASU 2016-02 retains a distinction between finance leases (i.e. capital leases under current GAAP) and operating leases. The classification criteria for distinguishing between finance leases and operating leases will be substantially similar to the classification criteria for distinguishing between capital leases and operating leases under current GAAP. 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	3 Months Ended
	Mar. 26, 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 March 26, 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): March 26, December 31, Cash and cash equivalents: Cash $ 10,861 $ 13,378 Money market funds 10,504 10,248 Total cash and cash equivalents 21,365 23,626 Marketable securities: Corporate debt securities 28,722 35,799 U.S. government agency securities 10,524 10,520 Commercial paper 3,649 3,645 Total marketable securities 42,895 49,964 Total cash, cash equivalents and marketable securities $ 64,260 $ 73,590 The carrying amounts of our money market funds approximate their fair values due to their nature, duration and short maturities. As of March 26, 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 $ 28,745 $ 2 $ (25 ) $ 28,722 U.S. government agency securities 10,530 — (6 ) 10,524 Commercial paper 3,649 — — 3,649 Total marketable securities $ 42,924 $ 2 $ (31 ) $ 42,895 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 March 26, 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 $ 42,924 $ 42,895

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 26, 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 March 26, 2016 and December 31, 2015 , based on the three-tier fair value hierarchy (in thousands): As of March 26, 2016 Level 1 Level 2 Total Money market funds $ 10,504 $ — $ 10,504 Corporate debt securities — 28,722 28,722 U.S. government agency securities — 10,524 10,524 Commercial paper — 3,649 3,649 Total $ 10,504 $ 42,895 $ 53,399 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 three months ended March 26, 2016 and March 28, 2015 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	3 Months Ended
	Mar. 26, 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 27, 2015 . 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 27, 2015 . 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 2015 annual impairment test that would more likely than not indicate that the carrying value of goodwill may have been impaired as of March 26, 2016 . Therefore, there was no impairment to the carrying value of the Company's goodwill as of March 26, 2016 . Intangible Assets Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of March 26, 2016 and December 31, 2015 are disclosed in the following table (in thousands): March 26, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (65,710 ) $ 3,254 $ 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 $ (120,450 ) $ 3,254 $ 123,704 $ (117,086 ) $ 6,618 Amortization expense was $3.4 million and $4.6 million for the three months ended March 26, 2016 and March 28, 2015 , respectively. As of March 26, 2016 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2016 $ 2,441 2017 813 Total $ 3,254

Balance Sheet Details

Balance Sheet Details	3 Months Ended
	Mar. 26, 2016
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): March 26, December 31, Accounts receivable $ 44,776 $ 48,319 Allowance for doubtful accounts (417 ) (501 ) Product return reserve (555 ) (663 ) Accounts receivable, net $ 43,804 $ 47,155 Inventory consisted of the following (in thousands): March 26, December 31, Raw materials $ 2,048 $ 2,209 Finished goods 39,079 45,458 Total inventory $ 41,127 $ 47,667 Property and equipment, net consisted of the following (in thousands): March 26, December 31, Test equipment $ 39,914 $ 39,035 Computer equipment and software 27,957 27,736 Furniture and fixtures 2,096 1,833 Leasehold improvements 6,554 6,554 Total 76,521 75,158 Accumulated depreciation and amortization (60,006 ) (58,009 ) Property and equipment, net $ 16,515 $ 17,149 Accrued liabilities consisted of the following (in thousands): March 26, December 31, Accrued compensation and related benefits $ 17,019 $ 13,809 Accrued warranty 9,152 9,564 Accrued professional and consulting fees 7,392 2,813 Accrued customer rebates 1,269 784 Accrued excess and obsolete inventory at contract manufacturers 1,038 1,011 Advance customer payments 971 1,094 Accrued non income related taxes 914 905 Accrued business travel expenses 854 580 Accrued insurance 791 — Accrued rent 396 381 Accrued freight 345 486 Income taxes payable 287 322 Accrued hosting services 240 466 Accrued other 3,133 3,297 Total accrued liabilities $ 43,801 $ 35,512 Deferred revenue consisted of the following (in thousands): March 26, December 31, 2015 Current: Product and services $ 6,536 $ 8,937 Extended warranty 3,266 3,187 9,802 12,124 Non-current: Product and services 45 58 Extended warranty 19,651 19,511 19,696 19,569 Total deferred revenue $ 29,498 $ 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	3 Months Ended
	Mar. 26, 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 three months ended March 26, 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 warranty for its hardware products. Hardware generally has a one , three or five -year 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. 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 March 26, March 28, Balance at beginning of period $ 9,564 $ 9,553 Warranty charged to cost of revenue 580 1,068 Utilization of warranty (619 ) (998 ) Adjustments to pre-existing warranty (373 ) — Balance at end of period $ 9,152 $ 9,623 Litigation From time to time, the Company is involved in various legal proceedings arising from the normal course of business activities. On September 16, 2010, the Company, two direct, wholly-owned subsidiaries of the Company, and Occam entered into an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”). In response to the announcement of the Merger Agreement on October 6, 2010, a purported class action complaint was filed by stockholders of Occam in the Delaware Court of Chancery styled as Steinhardt v. Howard-Anderson, et al. (Case No. 5878-VCL). On November 24, 2010, these stockholders filed an amended complaint (the “amended Steinhardt complaint”). The amended Steinhardt complaint named Occam (which has since been merged into Calix) and the members of the Occam board of directors as defendants. The amended Steinhardt complaint did not name Calix as a defendant. The amended Steinhardt complaint 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. The merger transaction was completed on February 22, 2011 (the “Effective Date”). On January 6, 2012, the Delaware court ruled on a motion for sanctions brought by the defendants against certain of the lead plaintiffs. The Delaware court found that lead plaintiffs Michael Steinhardt, Steinhardt Overseas Management, L.P., and Ilex Partners, L.L.C., collectively the “Steinhardt Plaintiffs,” had engaged in improper trading of Calix shares, and dismissed the Steinhardt Plaintiffs from the case with prejudice. The court further held that the Steinhardt Plaintiffs are: (i) barred from receiving any recovery from the litigation, (ii) required to self-report to the SEC, (iii) directed to disclose their improper trading in any future application to serve as lead plaintiff, and (iv) ordered to disgorge trading profits of $0.5 million , to be distributed to the remaining members of the class of former Occam stockholders. The Delaware court also granted the motion of the remaining lead plaintiffs, Herbert Chen and Derek Sheeler, for class certification, and certified Messrs. Chen and Sheeler as class representatives. The certified class is a non-opt-out class consisting of all owners of Occam common stock whose shares were converted to shares of Calix on the date of the merger transaction, with the exception of the defendants in the Delaware action and their affiliates. Chen and Sheeler, on behalf of the class of similarly situated former Occam stockholders, continued to seek an award of damages in an unspecified amount. Fact discovery in the case initially closed on April 30, 2013. On June 11, 2013, the plaintiffs filed their Second Amended Class Action Complaint for Breach of Fiduciary Duty (“Second Amended Complaint”). The Second Amended Complaint adds Occam's former CFO as a defendant, and alleges that each of the defendants 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 filed with the SEC on November 2, 2010. On July 17, 2013, attorneys representing all of the defendants named in the Second Amended Complaint filed Defendants' Opening Brief in Support of Their Motion for Summary Judgment, arguing that all defendants are entitled to summary judgment on all counts of the Second Amended Complaint. Plaintiffs' answering brief to the motion for summary judgment was filed on September 3, 2013, and defendants' reply brief was filed on October 4, 2013. A hearing on the motion for summary judgment was held on December 6, 2013. On April 8, 2014, the Delaware Court of Chancery issued an Opinion granting in part and denying in part the Defendants’ Motion for Summary Judgment. The ruling granted summary judgment on all claims as to Occam, the corporate entity, and accordingly, Occam was dismissed as a defendant in the action. The court also granted summary judgment in favor of those defendants who served solely as directors of Occam with respect to all claims alleging improper actions in connection with the Occam sale process. The court left in place the process-based claims against Occam’s former CEO and CFO, and declined to grant summary judgment on separate claims that the director and officer defendants breached their fiduciary duties by issuing a proxy statement for Occam’s stockholder vote that allegedly contained misleading disclosures and had material omissions. On June 12, 2014, the plaintiffs filed a Motion to Compel Production of Documents by Defendants and Jefferies & Company, Inc. ("Jefferies") and For Sanctions Against Defendants. This motion sought additional documents from defendants and from Jefferies, Occam’s former financial advisor, and requested that the court impose severe sanctions, up to and including a finding of liability against defendants. Defendants have rejected the suggestion that any additional documents should be produced and vigorously opposed the imposition of any sanctions. On September 3, 2014, the court denied the motion without prejudice as to defendants, directed counsel for the defendants to provide an affidavit clarifying the prior conduct of discovery, and ordered discovery into defendants’ document collection and review methodologies. The court also ordered Jefferies to produce additional documents. Plaintiffs then filed a motion requesting leave to amend their complaint to add Jefferies and Wilson Sonsini Goodrich & Rosati, P.C. ("Wilson Sonsini"), Occam’s counsel and former defense counsel in this lawsuit, as defendants. That motion was heard by the Court on March 23, 2015. At the hearing the Court vacated the existing April 20, 2015 trial date and indicated it would set a new trial date after ruling on the motion requesting leave to add additional parties. On July 16, 2015, the Court denied plaintiffs’ motion for leave to amend their complaint to add Jefferies as a defendant, but granted plaintiffs’ motion for leave to amend their complaint to add Wilson Sonsini as a defendant. On July 22, 2015, plaintiffs filed their Third Amended Complaint adding Wilson Sonsini as a defendant in the lawsuit. Defendants filed their answers to the Third Amended Complaint on September 8, 2015. 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. 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. 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. Further, the Company has incurred certain defense costs (as discussed in more detail below) for which its insurance carriers denied coverage or that are otherwise in excess of coverage. These costs were recorded as operating expense in the Company’s Consolidated Statement of Comprehensive Income (Loss) in the periods incurred. In connection with the Settlement (and separate from the settlement consideration), the Company would also receive a cash payment of approximately $4.5 million in partial recovery of such costs. The Settlement is subject to the approval of the Delaware Court of Chancery. As of March 26, 2016, the Company had not recorded any amounts related to this Settlement. Upon approval of the settlement, the Company expects to recognize the $4.5 million in partial recovery of out-of-pocket costs. See additional discussion in Note 13, “ Subsequent Event .” The Company and the defendants have denied and continue to deny each and all of the claims alleged in the litigation, and the Settlement does not assign or reflect any admission of fault, wrongdoing or liability as to any defendant. Since the closing of the merger, the Company has advanced defense costs related to this lawsuit. The Company has 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, under the engagement letter between Occam and Jefferies, the Company has obligations, under certain circumstances, to hold harmless and indemnify Jefferies against judgments, fines, settlements and expenses related to Jefferies’ engagement by Occam. The Company has paid fees and expenses incurred by Jefferies in connection with this matter pursuant to Jefferies indemnity demand under this agreement. The Company has incurred significant legal fees and costs defending this lawsuit and during the fiscal quarter ended March 26, 2016, the Company’s defense costs exhausted its available Directors & Officers liability insurance coverage. As described above, the legal proceedings have been protracted as plaintiffs continue to seek additional discovery following the court’s order re-opening discovery and, most recently, with the addition of Wilson Sonsini as a defendant in the action. The Company has also continued to incur certain expenses that were not covered by insurance, including the Company’s costs associated with the Jefferies indemnification obligations. For the fiscal quarter ended March 26, 2016, the Company recorded litigation defense costs and expenses in excess of its insurance coverage of $3.6 million as operating expense in the accompanying Condensed Consolidated Statements of Comprehensive Loss. The Company is not currently a party to any other legal proceedings that, if determined adversely to the Company, would individually or in the aggregate have a material adverse effect on the Company's business, operating results or financial condition. 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) certain agreements with the Company’s officers, directors, and 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
	Mar. 26, 2016
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 March 26, March 28, Numerator: Net loss $ (10,729 ) $ (11,930 ) Denominator: Weighted-average common shares outstanding 48,591 51,732 Basic and diluted net loss per common share $ (0.22 ) $ (0.23 ) Potentially dilutive shares, weighted average 5,500 5,625 For the three months ended March 28, 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 because their effect would be antidilutive. These antidilutive shares were primarily from stock options, restricted stock units and performance restricted stock awards. We have incurred a net loss for all periods presented, and therefore 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
	Mar. 26, 2016
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Equity Incentive Plans The Company maintains three equity incentive plans, the 2000 Stock Plan, 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 months ended March 26, 2016 , the Company did not grant stock options. During the three months ended March 26, 2016 , 2,312 stock options were exercised at a weighted-average exercise price of $5.85 per share. As of March 26, 2016 , unrecognized stock-based compensation expense of $2.9 million related to stock options, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 2.1 years. Restricted Stock Units During the three months ended March 26, 2016 , 111,875 RSUs were granted with a weighted-average grant date fair value of $7.42 per share. During the three months ended March 26, 2016 , 31,943 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 $0.1 million were remitted to the relevant taxing authorities during the three months ended March 26, 2016 . As of March 26, 2016 , 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. During the three months ended March 26, 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 March 26, 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 three months ended March 26, 2016 . As of March 26, 2016 , unrecognized stock-based compensation expense of $3.4 million related to PRSUs, net of estimated forfeitures, is expected to be recognized over a weighted-average period of 1.6 year. 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. 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 March 26, 2016 , there were 1,129,139 shares available for issuance under the ESPP. There were no shares purchased under the ESPP during the three months ended March 26, 2016 . As of March 26, 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 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 three months ended March 26, 2016 , the Company repurchased 1,789,287 shares of common stock for $12.8 million at an average price of $7.16 per share. As of March 26, 2016 , 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)	3 Months Ended
	Mar. 26, 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 March 26, 2016 March 28, 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) 65 (18 ) 47 39 (30 ) 9 Balance at end of period $ (29 ) $ (119 ) $ (148 ) $ (19 ) $ 108 $ 89 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 Loss.

Credit Facility

Credit Facility	3 Months Ended
	Mar. 26, 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 , which 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 leverage ratio of consolidated funded indebtedness to consolidated Adjusted EBITDA, as customarily defined and amended. 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 March 26, 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 March 26, 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 March 26, 2016 , the unamortized balance of debt issuance costs of $0.2 million were included within "Other assets" in the Company's Condensed Consolidated Balance Sheets.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 26, 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 March 26, March 28, Provision for income taxes $ 121 $ 91 Effective tax rate (1.1 )% (0.8 )% The income tax provision for the three months ended March 26, 2016 and March 28, 2015 consisted primarily of foreign income taxes. The effective tax rate for the three months ended March 26, 2016 and March 28, 2015 was determined using an estimated annual effective tax rate adjusted for discrete items, if any, that occurred during the respective period. The Company’s effective tax rate for the three months ended March 26, 2016 and March 28, 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 .

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 26, 2016
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event On April 14, 2016, the parties in the class action litigation captioned Chen v. Howard-Anderson, et al. (C.A. No. 5878-VCL) entered into a memorandum of understanding of a settlement in principle (“Settlement”) to resolve the claims pending before the Delaware Court of Chancery and related claims. This litigation, relating to the Company’s acquisition of Occam Networks, Inc., is described in further detail in Note 7. If the Settlement becomes final, the total settlement consideration paid for the benefit of the settlement class would be $35 million . Under the Settlement terms, the Company would not be responsible for contributing any portion of the settlement consideration. 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. Further, as disclosed in Note 7, the Company incurred certain defense costs for which its insurance carriers denied coverage. These costs were recorded as operating expense in the Company’s Consolidated Statement of Comprehensive Income (Loss) in the periods incurred. In connection with the Settlement, the Company will receive approximately $4.5 million in partial recovery of such costs. The Settlement is subject to approval by the court of notice to the class and settlement hearing before the court. The Company and the defendants have denied and continue to deny each and all of the claims alleged in the litigation, and the Settlement does not assign or reflect any admission of fault, wrongdoing or liability as to any defendant.

Significant Accounting Polici19

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 26, 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 includes provisions intended to simplify the following aspects related to how share-based payments are accounted for and presented in the financial statements: a. Accounting for Income Taxes: ASU 2016-09 requires recognition of all of the tax effects related to share-based payments at settlement (or expiration) through the statement of operations. Under the current GAAP, tax benefits in excess of compensation cost (“windfalls”) are recorded in equity, and tax deficiencies (“shortfalls”) are recorded in equity to the extent of previous windfalls, and then to the statement of operations. ASU 2016-09 is required to be applied prospectively to all excess tax benefits and tax deficiencies resulting from settlements after the date of adoption. ASU 2016-09 also removes the requirement to delay recognition of a windfall tax benefit until it reduces current taxes payable. Under the new guidance, the benefit will be recorded when it arises, subject to normal valuation allowance considerations. This change is required to be applied on a modified retrospective basis, with a cumulative-effect adjustment to opening retained earnings. 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. Either prospective or retrospective transition of this change in cash flow presentation is permitted. c. Forfeitures: ASU 2016-09 allows companies to make an accounting policy election to either estimate the number of awards that are expected to vest (current GAAP) or account for forfeitures when they occur. Estimates of forfeitures will still be required in certain circumstances, such as at the time of modification of an award or issuance of a replacement award in a business combination. If elected, the change to recognize forfeitures when they occur needs to be adopted using a modified retrospective approach, with a cumulative effect adjustment recorded to opening retained earnings. d. Minimum Statutory Tax Withholding Requirements: ASU 2016-09 allows companies to withhold an amount up to the employees’ maximum individual tax rate in the relevant jurisdiction without resulting in liability classification of the award. This provision is required to be adopted using a modified retrospective approach, with a cumulative-effect adjustment to opening retained earnings for any outstanding liability awards that qualify for equity classification under the ASU. 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. This change should be applied retrospectively. 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 increases transparency and comparability among companies by recognizing lease assets and lease liabilities on the balance sheet and disclosing key information about leasing arrangements. ASU 2016-02 requires a lessee to recognize in its balance sheet a liability to make lease payments (the lease liability) and a right-to-use asset representing its right to use the underlying asset for the lease term. The recognition, measurement, and presentation of expenses and cash flows arising from a lease by a lessee have not significantly changed from current GAAP. ASU 2016-02 retains a distinction between finance leases (i.e. capital leases under current GAAP) and operating leases. The classification criteria for distinguishing between finance leases and operating leases will be substantially similar to the classification criteria for distinguishing between capital leases and operating leases under current GAAP. 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 Ma20

Cash, Cash Equivalents and Marketable Securities (Tables)	3 Months Ended
	Mar. 26, 2016
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash, cash equivalents and marketable securities consisted of the following (in thousands): March 26, December 31, Cash and cash equivalents: Cash $ 10,861 $ 13,378 Money market funds 10,504 10,248 Total cash and cash equivalents 21,365 23,626 Marketable securities: Corporate debt securities 28,722 35,799 U.S. government agency securities 10,524 10,520 Commercial paper 3,649 3,645 Total marketable securities 42,895 49,964 Total cash, cash equivalents and marketable securities $ 64,260 $ 73,590
Amortized cost and fair value of marketable securities	As of March 26, 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 $ 28,745 $ 2 $ (25 ) $ 28,722 U.S. government agency securities 10,530 — (6 ) 10,524 Commercial paper 3,649 — — 3,649 Total marketable securities $ 42,924 $ 2 $ (31 ) $ 42,895 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 March 26, 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 $ 42,924 $ 42,895

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 26, 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 March 26, 2016 and December 31, 2015 , based on the three-tier fair value hierarchy (in thousands): As of March 26, 2016 Level 1 Level 2 Total Money market funds $ 10,504 $ — $ 10,504 Corporate debt securities — 28,722 28,722 U.S. government agency securities — 10,524 10,524 Commercial paper — 3,649 3,649 Total $ 10,504 $ 42,895 $ 53,399 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)	3 Months Ended
	Mar. 26, 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 March 26, 2016 and December 31, 2015 are disclosed in the following table (in thousands): March 26, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (65,710 ) $ 3,254 $ 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 $ (120,450 ) $ 3,254 $ 123,704 $ (117,086 ) $ 6,618
Expected future amortization	As of March 26, 2016 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2016 $ 2,441 2017 813 Total $ 3,254

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	3 Months Ended
	Mar. 26, 2016
Balance Sheet Related Disclosures [Abstract]
Summary of accounts receivable, net	Accounts receivable, net consisted of the following (in thousands): March 26, December 31, Accounts receivable $ 44,776 $ 48,319 Allowance for doubtful accounts (417 ) (501 ) Product return reserve (555 ) (663 ) Accounts receivable, net $ 43,804 $ 47,155
Summary of inventory	Inventory consisted of the following (in thousands): March 26, December 31, Raw materials $ 2,048 $ 2,209 Finished goods 39,079 45,458 Total inventory $ 41,127 $ 47,667
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): March 26, December 31, Test equipment $ 39,914 $ 39,035 Computer equipment and software 27,957 27,736 Furniture and fixtures 2,096 1,833 Leasehold improvements 6,554 6,554 Total 76,521 75,158 Accumulated depreciation and amortization (60,006 ) (58,009 ) Property and equipment, net $ 16,515 $ 17,149
Summary of accrued liabilities	Accrued liabilities consisted of the following (in thousands): March 26, December 31, Accrued compensation and related benefits $ 17,019 $ 13,809 Accrued warranty 9,152 9,564 Accrued professional and consulting fees 7,392 2,813 Accrued customer rebates 1,269 784 Accrued excess and obsolete inventory at contract manufacturers 1,038 1,011 Advance customer payments 971 1,094 Accrued non income related taxes 914 905 Accrued business travel expenses 854 580 Accrued insurance 791 — Accrued rent 396 381 Accrued freight 345 486 Income taxes payable 287 322 Accrued hosting services 240 466 Accrued other 3,133 3,297 Total accrued liabilities $ 43,801 $ 35,512
Summary of deferred revenue	Deferred revenue consisted of the following (in thousands): March 26, December 31, 2015 Current: Product and services $ 6,536 $ 8,937 Extended warranty 3,266 3,187 9,802 12,124 Non-current: Product and services 45 58 Extended warranty 19,651 19,511 19,696 19,569 Total deferred revenue $ 29,498 $ 31,693

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 26, 2016
Commitments and Contingencies Disclosure [Abstract]
Product warranty activities	Changes in the Company’s warranty reserve were as follows (in thousands): Three Months Ended March 26, March 28, Balance at beginning of period $ 9,564 $ 9,553 Warranty charged to cost of revenue 580 1,068 Utilization of warranty (619 ) (998 ) Adjustments to pre-existing warranty (373 ) — Balance at end of period $ 9,152 $ 9,623

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	3 Months Ended
	Mar. 26, 2016
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 March 26, March 28, Numerator: Net loss $ (10,729 ) $ (11,930 ) Denominator: Weighted-average common shares outstanding 48,591 51,732 Basic and diluted net loss per common share $ (0.22 ) $ (0.23 ) Potentially dilutive shares, weighted average 5,500 5,625

Accumulated Other Comprehensi26

Accumulated Other Comprehensive Income (Loss) (Tables)	3 Months Ended
	Mar. 26, 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 March 26, 2016 March 28, 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) 65 (18 ) 47 39 (30 ) 9 Balance at end of period $ (29 ) $ (119 ) $ (148 ) $ (19 ) $ 108 $ 89

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 26, 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 March 26, March 28, Provision for income taxes $ 121 $ 91 Effective tax rate (1.1 )% (0.8 )%

Significant Accounting Polici28

Significant Accounting Policies - Concentration Risk (Details) - Customer Concentration Risk - customer	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Revenue
Concentration Risk [Line Items]
Number of major customers	2	1
Accounts Receivable
Concentration Risk [Line Items]
Number of major customers	1
Largest Two Customers | Revenue
Concentration Risk [Line Items]
Concentration risk, percentage	29.00%	26.00%

Cash, Cash Equivalents and Ma29

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015	Mar. 28, 2015	Dec. 31, 2014
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 21,365	$ 23,626	$ 29,618	$ 48,829
Marketable securities	42,895	49,964
Total cash, cash equivalents and marketable securities	64,260	73,590
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities	28,722	35,799
U.S. government agency securities
Cash and Cash Equivalents [Line Items]
Marketable securities	10,524	10,520
Commercial paper
Cash and Cash Equivalents [Line Items]
Marketable securities	3,649	3,645
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	10,861	13,378
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 10,504	$ 10,248

Cash, Cash Equivalents and Ma30

Cash, Cash Equivalents and Marketable Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 42,924	$ 50,058
Gross Unrealized Gains	2	2
Gross Unrealized Losses	(31)	(96)
Fair Value	42,895	49,964
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,745	35,869
Gross Unrealized Gains	2	2
Gross Unrealized Losses	(25)	(72)
Fair Value	28,722	35,799
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,530	10,544
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(24)
Fair Value	10,524	10,520
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,649	3,645
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 3,649	$ 3,645

Cash, Cash Equivalents and Ma31

Cash, Cash Equivalents and Marketable Securities - Contractual Maturity (Details) $ in Thousands	Mar. 26, 2016USD ($)
Cash and Cash Equivalents [Abstract]
Marketable securities due in 1 year or less, amortized cost	$ 42,924
Marketable securities due in 1 year or less, fair value	$ 42,895

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 42,895	$ 49,964
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	53,399	60,212
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	10,504	10,248
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	42,895	49,964
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	28,722	35,799
Corporate debt securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	28,722	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	28,722	35,799
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,524	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	10,524	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	10,524	10,520
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	3,649	3,645
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	3,649	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	0
Commercial paper | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	3,649	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	10,504	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	10,504	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 Asset33

Goodwill and Intangible Assets - Textual (Details) - USD ($)	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, impairment loss	$ 0
Amortization expense	$ 3,364,000	$ 4,640,000

Goodwill and Intangible Asset34

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 123,704	$ 123,704
Accumulated Amortization	(120,450)	(117,086)
Net	3,254	6,618
Core developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	68,964	68,964
Accumulated Amortization	(65,710)	(64,047)
Net	3,254	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 Asset35

Goodwill and Intangible Assets - Expected Future Amortization (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Expected future amortization
Remainder of 2016	$ 2,441
2,017	813
Net	$ 3,254	$ 6,618

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Summary of accounts receivable, net
Accounts receivable	$ 44,776	$ 48,319
Allowance for doubtful accounts	(417)	(501)
Product return reserve	(555)	(663)
Accounts receivable, net	$ 43,804	$ 47,155

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Summary of inventory, net
Raw materials	$ 2,048	$ 2,209
Finished goods	39,079	45,458
Total inventory	$ 41,127	$ 47,667

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Summary of property and equipment, net
Property and equipment, gross	$ 76,521	$ 75,158
Accumulated depreciation and amortization	(60,006)	(58,009)
Property and equipment, net	16,515	17,149
Test equipment
Summary of property and equipment, net
Property and equipment, gross	39,914	39,035
Computer equipment and software
Summary of property and equipment, net
Property and equipment, gross	27,957	27,736
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	2,096	1,833
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	$ 6,554	$ 6,554

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Summary of accrued liabilities
Accrued compensation and related benefits	$ 17,019	$ 13,809
Accrued warranty	9,152	9,564
Accrued professional and consulting fees	7,392	2,813
Accrued customer rebates	1,269	784
Accrued excess and obsolete inventory at contract manufacturers	1,038	1,011
Advance customer payments	971	1,094
Accrued non income related taxes	914	905
Accrued business travel expenses	854	580
Accrued insurance	791	0
Accrued rent	396	381
Accrued freight	345	486
Accrued hosting services	287	322
Income taxes payable	240	466
Accrued other	3,133	3,297
Total accrued liabilities	$ 43,801	$ 35,512

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 26, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 9,802	$ 12,124
Deferred revenue, noncurrent	19,696	19,569
Deferred revenue	29,498	31,693
Product and services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	6,536	8,937
Deferred revenue, noncurrent	19,651	19,511
Extended warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	3,266	3,187
Deferred revenue, noncurrent	$ 45	$ 58

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details) $ in Millions	Apr. 14, 2016USD ($)	Jan. 06, 2012USD ($)	Sep. 16, 2010Subsidiary	Mar. 26, 2016USD ($)
Commitments and Contingencies [Line Items]
Warranty period				3 years
Number of subsidiaries | Subsidiary			2
Trading profits		$ 0.5
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]
Litigation defense costs and expenses in excess of insurance coverage				$ 3.6
Pending Litigation | Subsequent Event | Chen v. Howard-Anderson, et al.
Commitments and Contingencies [Line Items]
Settlement consideration to be paid, if settlement becomes final	$ 35
Recovery of settlement costs	$ 4.5

Commitments and Contingencies42

Commitments and Contingencies - Product Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Product warranty activities [Roll Forward]
Balance at beginning of period	$ 9,564	$ 9,553
Warranty charged to cost of revenue	580	1,068
Utilization of warranty	(619)	(998)
Adjustments to pre-existing warranty	(373)	0
Balance at end of period	$ 9,152	$ 9,623

Net Loss per Common Share - Bas

Net Loss per Common Share - Basic and Diluted Shares Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Numerator:
Net loss	$ (10,729)	$ (11,930)
Denominator:
Weighted-average common shares outstanding (in shares)	48,591	51,732
Basic and diluted net loss per common share (in dollars per share)	$ (0.22)	$ (0.23)
Potentially dilutive shares, weighted average (in shares)	5,500	5,625

Stockholders' Equity - Textual

Stockholders' Equity - Textual (Details)	3 Months Ended		12 Months Ended
	Mar. 26, 2016USD ($)Plan$ / sharesshares	Mar. 28, 2015USD ($)	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | Plan	3
Stock options granted	0
Stock options exercised	2,312
Weighted-average exercise price per share, stock options | $ / shares	$ 5.85
Unrecognized stock-based compensation expense, stock options | $	$ 2,900,000
Weighted-average amortization period	2 years 1 month
Taxes paid for awards vested under equity incentive plans | $	$ 251,000	$ 506,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period	2 years 5 months
Awards granted	111,875
Weighted-average grant date fair value per share | $ / shares	$ 7.42
Awards vested	31,943
Taxes paid for awards vested under equity incentive plans | $	$ 100,000
Unrecognized stock-based compensation expense | $	$ 12,600,000
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	0
Awards vested	0
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 | $	$ 200,000
ESPP, maximum employee payroll deduction percentage	15.00%
ESPP, maximum number of shares per employee	2,000
ESPP, discounted purchase price percentage	85.00%
Shares available for issuance under the ESPP	1,129,139
Shares issued under the ESPP	0
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period	1 year 7 months
Awards granted	550,000
Weighted-average grant date fair value per share | $ / shares	$ 7.42
Taxes paid for awards vested under equity incentive plans | $	$ 100,000
Unrecognized stock-based compensation expense | $	$ 3,400,000
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	44,992
Performance Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period	1 year		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			3 years
Target performance rate	200.00%
Transition And Separation Agreement with Roger Weingarth
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value recognized for accelerated stock awards | $		$ 0
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	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 ($)	3 Months Ended	11 Months Ended
	Mar. 26, 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	1,789,287	5,329,817
Shares repurchased, value	$ 12,800,000
Average price per share	$ 7.16	$ 7.50

Accumulated Other Comprehensi46

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 235,785
Balance at end of period	214,778
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(94)	$ (58)
Other comprehensive income (loss)	65	39
Balance at end of period	(29)	(19)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(101)	138
Other comprehensive income (loss)	(18)	(30)
Balance at end of period	(119)	108
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(195)	80
Other comprehensive income (loss)	47	9
Balance at end of period	$ (148)	$ 89

Credit Facility - Textual (Deta

Credit Facility - Textual (Details)	Jul. 29, 2013USD ($)	Jun. 30, 2013USD ($)	Mar. 26, 2016USD ($)payment	Mar. 28, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2013USD ($)
Credit Facility [Line Items]
Maximum borrowing capacity	$ 50,000,000
Maturity date	Sep. 30, 2018
Restricted cash released			$ 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 | 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			$ 200,000
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 - Schedule of Inco

Income Taxes - Schedule of Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 26, 2016	Mar. 28, 2015
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 121	$ 91
Effective tax rate	(1.10%)	(0.80%)

Subsequent Event (Details)

Subsequent Event (Details) - Pending Litigation - Chen v. Howard-Anderson, et al. - Subsequent Event $ in Millions	Apr. 14, 2016USD ($)
Subsequent Event [Line Items]
Settlement consideration to be paid, if settlement becomes final	$ 35
Recovery of settlement costs	$ 4.5