Calix (CALX) 10-Q 30 Oct 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 26, 2015	Oct. 22, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	CALIX, INC
Entity Central Index Key	1,406,666
Document Type	10-Q
Document Period End Date	Sep. 26, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		50,809,976

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 36,194	$ 48,829
Marketable securities	57,659	62,850
Restricted cash	0	295
Accounts receivable, net	48,188	30,744
Inventory	43,769	46,753
Deferred cost of revenue	2,998	5,080
Prepaid expenses and other current assets	8,311	12,936
Total current assets	197,119	207,487
Property and equipment, net	18,484	20,144
Goodwill	116,175	116,175
Intangible assets, net	11,259	25,179
Other assets	1,091	1,236
Total assets	344,128	370,221
Current liabilities:
Accounts payable	16,784	23,629
Accrued liabilities	38,280	39,443
Deferred revenue	11,414	12,722
Total current liabilities	66,478	75,794
Long-term portion of deferred revenue	19,390	19,393
Other long-term liabilities	1,700	2,443
Total liabilities	$ 87,568	$ 97,630
Commitments and contingencies (See Note 7)
Stockholders’ equity:
Preferred stock, $0.025 par value; 5,000,000 shares authorized; no shares issued and outstanding as of September 26, 2015 and December 31, 2014	$ 0	$ 0
Common stock, $0.025 par value; 100,000,000 shares authorized; 52,624,475 shares issued and 51,177,649 shares outstanding as of September 26, 2015, and 51,628,257 shares issued and outstanding as of December 31, 2014	1,316	1,291
Additional paid-in capital	813,776	801,810
Accumulated other comprehensive income (loss)	(31)	80
Accumulated deficit	(547,377)	(530,590)
Treasury stock, 1,446,826 shares as of September 26, 2015	(11,124)	0
Total stockholders’ equity	256,560	272,591
Total liabilities and stockholders’ equity	$ 344,128	$ 370,221

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 26, 2015	Dec. 31, 2014
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	52,624,475	51,628,257
Common stock, shares outstanding	51,177,649	51,628,257
Treasury stock, shares	1,446,826	0

Condensed Consolidated Statemen

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Revenue		$ 112,297	$ 105,769	$ 302,464	$ 289,594
Cost of revenue:
Products and services	[1]	57,096	58,600	152,308	156,981
Amortization of intangible assets		2,088	2,089	6,264	6,265
Total cost of revenue		59,184	60,689	158,572	163,246
Gross profit		53,113	45,080	143,892	126,348
Operating expenses:
Research and development	[1]	22,120	19,930	66,885	59,104
Sales and marketing	[1]	18,424	18,717	57,398	54,562
General and administrative	[1]	9,140	7,625	28,728	22,557
Amortization of intangible assets		2,552	2,552	7,656	7,656
Total operating expenses		52,236	48,824	160,667	143,879
Income (loss) from operations		877	(3,744)	(16,775)	(17,531)
Interest and other income (expense), net:
Interest income		297	52	1,014	86
Interest expense		(263)	(59)	(921)	(174)
Other income (expense), net		196	18	273	121
Income (loss) before provision for income taxes		1,107	(3,733)	(16,409)	(17,498)
Provision for income taxes		185	115	378	328
Net income (loss)		$ 922	$ (3,848)	$ (16,787)	$ (17,826)
Net income (loss) per common share:
Basic (in dollars per share)		$ 0.02	$ (0.08)	$ (0.32)	$ (0.35)
Diluted (in dollars per share)		$ 0.02	$ (0.08)	$ (0.32)	$ (0.35)
Weighted-average number of shares used to compute net income (loss) per common share:
Basic (in shares)		51,756	51,048	51,814	50,635
Diluted (in shares)		52,016	51,048	51,814	50,635
Other comprehensive income (loss), net of tax:
Unrealized gains (losses) on available-for-sale marketable securities adjustment, net		$ 30	$ (13)	$ 66	$ (38)
Foreign currency translation adjustments, net		(196)	(7)	(177)	(13)
Total other comprehensive income (loss), net of tax		(166)	(20)	(111)	(51)
Comprehensive income (loss)		756	(3,868)	(16,898)	(17,877)
Stock-based compensation		2,590	3,813	10,593	12,119
Cost of revenue
Other comprehensive income (loss), net of tax:
Stock-based compensation		163	206	549	914
Research and development
Other comprehensive income (loss), net of tax:
Stock-based compensation		964	1,207	3,659	3,693
Sales and marketing
Other comprehensive income (loss), net of tax:
Stock-based compensation		688	1,316	3,769	4,146
General and administrative
Other comprehensive income (loss), net of tax:
Stock-based compensation		$ 775	$ 1,084	$ 2,616	$ 3,366
[1]	Includes stock-based compensation as follows: Three Months Ended September 26, 2015 and September 27, 2014, Six Months Ended September 26, 2015 and September 27, 2014: Cost of revenue - $163, $206, $549, $914; Research and development - $964, $1,207, $3,659, $3,693; Sales and marketing - $688, $1,316, $3,769, $4,146; General administrative - $775, $1,084, $2,616, $3,366; Total - $2,590, $3,813, $10,593, $12,119.

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014
Operating activities:
Net loss	$ (16,787)	$ (17,826)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	7,602	6,772
Loss on retirement of property and equipment	14	41
Amortization of intangible assets	13,920	13,921
Amortization of premiums related to available-for-sale securities	743	302
Gain on sale of available-for-sale securities	0	(1)
Stock-based compensation	10,593	12,119
Changes in operating assets and liabilities:
Restricted cash	295	0
Accounts receivable, net	(17,443)	739
Inventory	2,983	7,226
Deferred cost of revenue	2,082	9,742
Prepaid expenses and other assets	4,181	(315)
Accounts payable	(6,841)	(9,904)
Accrued liabilities	(1,055)	5,520
Deferred revenue	(1,312)	(14,391)
Other long-term liabilities	(167)	597
Net cash provided by (used in) operating activities	(1,192)	14,542
Investing activities:
Purchases of property and equipment	(5,943)	(9,481)
Purchases of marketable securities	(46,750)	(49,356)
Sales of marketable securities	0	615
Maturities of marketable securities	51,265	0
Net cash used in investing activities	(1,428)	(58,222)
Financing activities:
Proceeds from exercise of stock options	625	429
Proceeds from employee stock purchase plan	2,865	2,453
Payments for repurchases of common stock	(11,124)	0
Taxes paid for awards vested under equity incentive plans	(2,093)	(2,505)
Net cash provided by (used in) financing activities	(9,727)	377
Effect of exchange rate changes on cash and cash equivalents	(288)	(45)
Net decrease in cash and cash equivalents	(12,635)	(43,348)
Cash and cash equivalents at beginning of period	48,829	82,747
Cash and cash equivalents at end of period	$ 36,194	$ 39,399

Company and Basis of Presentati

Company and Basis of Presentation	9 Months Ended
	Sep. 26, 2015
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, 2014 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, 2014 . The Company's fiscal year begins on January 1st and ends on December 31st. Quarterly periods are based on a 4-4-5 fiscal calendar with the first, second and third fiscal quarters ending on the 13th Saturday of each fiscal period. As a result, the Company had one fewer day in the nine months ended September 26, 2015 than in the nine months ended September 27, 2014 , and the same number of days in the three months ended September 26, 2015 as in the three months ended September 27, 2014 . The preparation of financial statements in conformity with GAAP for interim financial reporting requires management to make estimates and assumptions that affect the amounts reported in the condensed consolidated financial statements and accompanying notes. Actual results could differ from those estimates.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 26, 2015
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, 2014 . The following are added in the summary of the Company's significant accounting policies during the nine months ended September 26, 2015 and will be included in our Annual Report on Form 10-K for the year ending December 31, 2015 . Legal Fees The Company incurs legal expenses related to disputes, litigation and other legal actions in the ordinary course of business. Legal fees, including those legal defense costs expected to be incurred in connection with a loss contingency, are expensed as incurred in the period that the related services are received. In the event the Company has insurance coverage for legal defense costs incurred and the likelihood of reimbursement is assured, legal defense costs recognized in a period are reduced by the amount recoverable from the insurance. A receivable is recognized for the portion of legal costs recoverable under the insurance at the time such legal costs are incurred and accrued. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("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 potential impact on its financial statements from adopting this new guidance.

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	9 Months Ended
	Sep. 26, 2015
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents and Marketable Securities	Cash, Cash Equivalents and Marketable Securities The Company has invested its excess cash primarily in money market funds and highly liquid marketable securities such as corporate debt instruments, U.S. government agency securities and commercial paper. The Company considers all investments with maturities of three months or less when purchased to be cash equivalents. Marketable securities represent highly liquid corporate debt instruments, U.S. government agency securities and commercial paper with maturities greater than 90 days at date of purchase. Marketable securities with maturities greater than one year are classified as current because management considers all marketable securities to be available for current operations. Cash equivalents are stated at amounts that approximate fair value based on quoted market prices. Marketable securities are recorded at their fair values. The Company’s investments have been classified and accounted for as available-for-sale. Such investments are recorded at fair value and unrealized holding gains and losses are reported as a separate component of accumulated other comprehensive income (loss) in the stockholders’ equity until realized. Realized gains and losses on sales of marketable securities, if any, are determined on the specific identification method and are reclassified from accumulated other comprehensive income (loss) to results of operations as other income (expense). The Company, to date, has not determined that any of the unrealized losses on its investments are considered to be other-than-temporary. The Company reviews its investment portfolio to determine if any security is other-than-temporarily impaired, which would require the Company to record an impairment charge in the period any such determination is made. In making this judgment, the Company evaluates, among other things: the duration and extent to which the fair value of a security is less than its cost; the financial condition of the issuer and any changes thereto; and the Company’s intent and ability to hold its investment for a period of time sufficient to allow for any anticipated recovery in market value, or whether the Company will more likely than not be required to sell the security before recovery of its amortized cost basis. The Company has evaluated its investments as of September 26, 2015 and has determined that no investments with unrealized losses are other-than-temporarily impaired. No investments have been in a continuous loss position greater than one year. Cash, cash equivalents and marketable securities consisted of the following (in thousands): September 26, December 31, Cash and cash equivalents: Cash $ 19,675 $ 17,866 Money market funds 16,519 30,963 Total cash and cash equivalents 36,194 48,829 Marketable securities: Corporate debt securities 44,802 61,050 U.S. government agency securities 10,564 — Commercial paper 2,293 1,800 Total marketable securities 57,659 62,850 Total cash, cash equivalents and marketable securities $ 93,853 $ 111,679 The carrying amounts of our money market funds approximate their fair values due to their nature, duration and short maturities. As of September 26, 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 $ 44,796 $ 16 $ (10 ) $ 44,802 U.S. government agency securities 10,562 2 — 10,564 Commercial paper 2,293 — — 2,293 Total marketable securities $ 57,651 $ 18 $ (10 ) $ 57,659 As of December 31, 2014 , 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 $ 61,108 $ 1 $ (59 ) $ 61,050 Commercial paper 1,800 — — 1,800 Total marketable securities $ 62,908 $ 1 $ (59 ) $ 62,850 As of September 26, 2015 , 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 $ 37,139 $ 37,139 Due in 1-2 years 20,512 20,520 Total marketable securities $ 57,651 $ 57,659

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 26, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements In accordance with Accounting Standard Codification ("ASC") Topic 820, Fair Value Measurements and Disclosures , (“ASC Topic 820”), the Company measures its cash equivalents and marketable securities at fair value on a recurring basis. ASC Topic 820 clarifies that fair value is an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, ASC Topic 820 establishes a three-tier value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1 – Observable inputs that reflect quoted prices (unadjusted) for identical assets or liabilities in active markets. Level 2 – Observable inputs other than quoted prices included in Level 1 for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-driven valuations in which all significant inputs and significant value drivers are observable in active markets. Level 3 – Unobservable inputs to the valuation derived from fair valuation techniques in which one or more significant inputs or significant value drivers are unobservable. The following table sets forth the Company's financial assets measured at fair value on a recurring basis as of September 26, 2015 and December 31, 2014 , based on the three-tier fair value hierarchy (in thousands): As of September 26, 2015 Level 1 Level 2 Total Money market funds $ 16,519 $ — $ 16,519 Corporate debt securities — 44,802 44,802 U.S. government agency securities — 10,564 10,564 Commercial paper — 2,293 2,293 Total $ 16,519 $ 57,659 $ 74,178 As of December 31, 2014 Level 1 Level 2 Total Money market funds $ 30,963 $ — $ 30,963 Corporate debt securities — 61,050 61,050 Commercial paper — 1,800 1,800 Total $ 30,963 $ 62,850 $ 93,813 The fair values of money market funds classified as Level 1 were derived from quoted market prices as active markets for these instruments exist. The fair values of corporate debt securities, U.S. government agency securities and commercial paper classified as Level 2 were derived from quoted market prices for similar instruments indexed to prevailing market yield rates. The Company has no Level 3 financial assets. The Company did not have any transfers between Level 1 and Level 2 of the fair value hierarchy during the nine months ended September 26, 2015 and September 27, 2014 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 26, 2015
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 were no events or changes in circumstances during the three months ended September 26, 2015 that would more likely than not indicate that the carrying value of goodwill may have been impaired subsequent to the 2015 annual impairment test. As of September 26, 2015 , there was no impairment to the carrying value of the Company's goodwill. Intangible Assets Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of September 26, 2015 and December 31, 2014 are disclosed in the following table (in thousands): September 26, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (61,958 ) $ 7,006 $ 68,964 $ (55,694 ) $ 13,270 Customer relationships 54,740 (50,487 ) 4,253 54,740 (42,831 ) 11,909 Total intangible assets, excluding goodwill $ 123,704 $ (112,445 ) $ 11,259 $ 123,704 $ (98,525 ) $ 25,179 Amortization expense was $4.6 million for the three months ended September 26, 2015 and September 27, 2014 . Amortization expense was $13.9 million for the nine months ended September 26, 2015 and September 27, 2014 . As of September 26, 2015 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2015 $ 4,640 2016 5,805 2017 814 Total $ 11,259

Balance Sheet Details

Balance Sheet Details	9 Months Ended
	Sep. 26, 2015
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): September 26, December 31, Accounts receivable $ 49,132 $ 31,493 Allowance for doubtful accounts (405 ) (241 ) Product return reserve (539 ) (508 ) Accounts receivable, net $ 48,188 $ 30,744 Inventory consisted of the following (in thousands): September 26, December 31, Raw materials $ 2,259 $ 3,180 Finished goods 41,510 43,573 Total inventory $ 43,769 $ 46,753 Property and equipment, net consisted of the following (in thousands): September 26, December 31, Test equipment $ 40,501 $ 40,766 Computer equipment and software 28,061 30,355 Furniture and fixtures 1,835 1,852 Leasehold improvements 6,553 6,550 Total 76,950 79,523 Accumulated depreciation and amortization (58,466 ) (59,379 ) Property and equipment, net $ 18,484 $ 20,144 Accrued liabilities consisted of the following (in thousands): September 26, December 31, Accrued compensation and related benefits $ 16,547 $ 15,782 Accrued warranty 8,984 9,553 Accrued professional and consulting fees 3,016 5,860 Accrued customer rebates 1,327 851 Accrued excess and obsolete inventory at contract manufacturers 1,237 888 Accrued business travel expenses 1,024 1,414 Sales and use tax payable 1,000 397 Advance customer payments 699 364 Accrued business events 543 — Accrued rent 385 412 Accrued freight 277 303 Income taxes payable 245 269 Accrued other 2,996 3,350 Total accrued liabilities $ 38,280 $ 39,443 Deferred revenue consisted of the following (in thousands): September 26, December 31, 2014 Product and services - current $ 8,463 $ 9,753 Extended warranty - current 2,951 2,969 Extended warranty - non-current 19,358 19,211 Product and services - non-current 32 182 Total deferred revenue $ 30,804 $ 32,115 Deferred cost of revenue consisted entirely of costs incurred for products and services for which revenues have been deferred .

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 26, 2015
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, 2014 are disclosed in our Annual Report on Form 10-K, and have not changed materially during the nine months ended September 26, 2015 . 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 adequacy of the accrual is reviewed on a periodic basis and adjusted, if necessary, based on additional information as it becomes available. Changes in the Company’s warranty reserve were as follows (in thousands): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Balance at beginning of period $ 9,325 $ 10,638 $ 9,553 $ 10,856 Warranty charged to cost of revenue 781 839 2,929 3,364 Utilization of warranty (722 ) (452 ) (3,098 ) (3,195 ) Adjustments to pre-existing warranty (400 ) (250 ) (400 ) (250 ) Balance at end of period $ 8,984 $ 10,775 $ 8,984 $ 10,775 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: 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, continue to seek an award of damages in an unspecified amount. Fact discovery in the case 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 Court of Chancery of the State of Delaware 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 is no longer 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. Those proceedings are ongoing, but the plaintiffs have indicated that they do not intend to seek any sanctions against the defendants at this time. Instead, plaintiffs filed a motion requesting leave to amend their complaint to add Jefferies and Wilson Sonsini Goodrich & Rosati, P.C. ("Wilson Sonsini"), 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 for this matter has been tentatively scheduled for the weeks of April 11 and April 18 in 2016 before the Delaware Court of Chancery. The Company continues to believe that the allegations in this action are without merit and intends to continue to vigorously contest the action as it moves forward toward trial. However, there can be no assurance that the defendants will be successful in defending this ongoing action. Although Occam is no longer a defendant in this lawsuit, the Company has continued to advance 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 who remain 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. Such indemnification obligations may ultimately result in the payment of indemnification amounts by the Company. 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, and Jefferies has demanded that the Company indemnify Jefferies in connection with this litigation under this agreement. The Company has begun to pay fees and expenses of Jefferies in connection with this matter, and expects that it will make additional payments as the matter proceeds, though at this time the Company is not able to estimate the amount of any future payments. The Company continues to incur significant legal fees and costs defending this lawsuit. The Company currently believes that its defense costs related to indemnity obligations will exceed its remaining available Directors & Officers liability insurance coverage as the matter proceeds to trial. As described above, the legal proceedings have been protracted as plaintiffs continue to seek additional discovery and, most recently, with the addition of Wilson Sonsini as a defendant in the action. The Company has also incurred certain expenses that are not covered by insurance. Following Jefferies' demand for indemnification the Company notified Occam’s insurance carriers, and such carriers have advised in writing that they do not believe the Jefferies indemnification obligations are covered by the Company’s insurance. Thus, the Company’s indemnification obligations to Jefferies that apply to this lawsuit will not be covered by insurance. The Company’s indemnity obligations that are in excess of its insurance coverage could be material, particularly if there is an adverse result at trial, and could have a material adverse effect on the Company’s business, operating results or financial condition. The outcome of the above litigation matter is undeterminable at this time and the Company cannot currently estimate a reasonably possible range of loss for this action. We continue to believe that plaintiffs’ claims are without merit under applicable law. At this time, based on the status of the legal proceedings and the court’s rulings to date on the lawsuit, there remain significant issues of fact and law that are yet to be resolved. In April 2014, although the court partially granted defendants’ motion for summary judgment, the court also denied part of the motion, ruling instead that the remaining issues should be adjudicated at trial. In September 2014, the court issued a ruling allowing further discovery into the underlying facts. This additional discovery continues to be in progress. In the court’s July 2015 order, plaintiffs were granted leave to file an amended complaint to add Wilson Sonsini as a defendant. The addition of Wilson Sonsini as a defendant gives rise to a number of material issues of law and fact regarding Wilson Sonsini’s potential aiding and abetting liability, its impact on the claims against the Occam defendants, and the allocation of any damages award. Furthermore, as previously noted, the plaintiffs have not communicated any specific demand for damages. However, the plaintiffs’ valuation expert has opined that the fair value of Occam’s common stock on the Effective Date exceeded the merger consideration by between $7.77 and $9.65 per share. Defendants’ valuation expert has opined that the fair value of Occam’s common stock on the Effective Date was less than the merger consideration. The Company estimates that as of the Effective Date, the class held approximately 15,147,085 shares of Occam’s common stock. In addition to the difference between the fair value of Occam’s common stock on the Effective Date and the merger consideration, the plaintiffs also seek an award of attorneys’ fees and costs, pre-judgment interest relating back to the Effective Date, and post-judgment interest. Because of these reasons, at this time, the Company is unable to quantify its indemnification risk or estimate a reasonably possible range of loss for this action. We intend to defend this case vigorously as we continue to believe the claims to be without merit. 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.

Net Income (Loss) per Common Sh

Net Income (Loss) per Common Share	9 Months Ended
	Sep. 26, 2015
Earnings Per Share [Abstract]
Net Income (Loss) per Common Share	Net Income (Loss) per Common Share The following table sets forth the computation of basic and diluted net income (loss) per common share for the periods indicated (in thousands, except per share data): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Numerator: Net income (loss) $ 922 $ (3,848 ) $ (16,787 ) $ (17,826 ) Denominator: Weighted-average common shares outstanding used to compute basic net income (loss) per share 51,756 51,048 51,814 50,635 Effect of dilutive common stock equivalents 260 — — — Weighted-average common shares outstanding used to compute diluted net income (loss) per share 52,016 51,048 51,814 50,635 Basic net income (loss) per common share $ 0.02 $ (0.08 ) $ (0.32 ) $ (0.35 ) Diluted net income (loss) per common share $ 0.02 $ (0.08 ) $ (0.32 ) $ (0.35 ) Potentially dilutive shares, weighted average 5,244 5,262 6,062 5,011 For all periods presented, 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. Basic net income (loss) per share is calculated by dividing net income (loss) by the weighted-average number of common shares outstanding during the reporting period. Diluted net income per share is calculated by using the weighted-average number of common shares outstanding during the period, adjusted for all dilutive potential common shares, which includes the exercise of stock options, the release of restricted stock units and performance restricted stock units, and purchase of shares pursuant to the Company's ESPP, to the extent these shares are dilutive. The dilutive effect of these common stock equivalents is reflected in diluted earnings per share by application of the treasury stock method. For all periods presented where the Company reported a net loss, diluted net loss per common share is the same as basic net loss per common share, since the effect of all potentially dilutive securities is antidilutive. Potentially dilutive shares are excluded from the computation of diluted net loss per common share when their effect is antidilutive. These antidilutive shares were primarily from stock options, restricted stock units and performance restricted stock awards.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 26, 2015
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 March 4, 2015 . 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 September 26, 2015 , the Company did not grant stock options. During the nine months ended September 26, 2015 , the Company granted 200,000 stock options at a weighted-average grant date fair value of $4.56 per share. During the three months ended September 26, 2015 , 6,301 stock options were exercised at a weighted-average exercise price of $5.49 per share. During the nine months ended September 26, 2015 , 94,987 stock options were exercised at a weighted-average exercise price of $6.58 per share. As of September 26, 2015 , unrecognized stock-based compensation expense of $8.0 million related to stock options, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 2.9 years. Restricted Stock Units During the three months ended September 26, 2015 , 165,300 RSUs were granted with a weighted-average grant date fair value of $7.48 per share. During the nine months ended September 26, 2015 , 1,521,761 RSUs were granted with a weighted-average grant date fair value of $8.57 per share. During the three months ended September 26, 2015 , 110,637 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 $0.5 million were remitted to the relevant taxing authorities during the three months ended September 26, 2015 . During the nine months ended September 26, 2015 , 408,471 RSUs vested, net of shares withheld at the then-current value equivalent to the employees' minimum statutory obligation for applicable income and other employment taxes, and were converted to an equivalent number of shares of common stock. Taxes withheld from employees of $1.5 million were remitted to the relevant taxing authorities during the nine months ended September 26, 2015 . As of September 26, 2015 , unrecognized stock-based compensation expense of $15.4 million related to RSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 2.8 years. Performance Restricted Stock Units In 2012, the Company commenced granting 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 under ASC Topic 718, Compensation - Stock Compensation ("ASC Topic 718"). 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 and nine months ended September 26, 2015 , no PRSUs were granted. During the three months ended September 26, 2015 , no PRSUs vested and were converted into shares of common stock. During the nine months ended September 26, 2015 , 147,916 PRSUs vested and were converted into 92,359 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 $0.5 million were remitted to the relevant taxing authorities during the nine months ended September 26, 2015 . As of September 26, 2015 , unrecognized stock-based compensation expense of $0.3 million related to PRSUs, net of estimated forfeitures, was expected to be recognized over a weighted-average period of 0.5 year. Restricted Stock Awards During the three and nine months ended September 26, 2015 , no RSAs were granted. Upon the vesting of RSAs during the three months ended September 26, 2015 , taxes withheld from employees of $0.1 million were remitted to the relevant taxing authorities. Upon the vesting of RSAs during the nine months ended September 26, 2015 , taxes withheld from employees of $0.2 million were remitted to the relevant taxing authorities. As of September 26, 2015 , there were no outstanding RSAs and no remaining unrecognized stock-based compensation expense. 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 ESPP are six-month periods commencing on June 1 and December 1 of each year. The Company changed the ESPP offering periods in 2015 where each six-month offering periods will end on May 1 and November 1 of each year. The offering period which started on June 1, 2015 will then be shortened to five months and will end on November 1, 2015. The subsequent offering periods will then revert back to the six-month periods commencing on November 2 and May 2 of each year. 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 end date of each six-month offering period. As of September 26, 2015 , there were 1,469,648 shares available for issuance under the ESPP. There were no shares purchased under the ESPP during the three months ended September 26, 2015 . During the nine months ended September 26, 2015 , 421,335 shares were purchased under the ESPP. As of September 26, 2015 , unrecognized stock-based compensation expense of $0.2 million related to the ESPP was expected to be recognized over a remaining service period of 1 month . Stock-Based Compensation Expense In accordance with ASC Topic 718, 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. 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. The Company estimates the fair value of stock options at the grant date using the Black-Scholes option-pricing model. This model requires the use of the following assumptions: (i) Expected volatility of the Company's common stock - The Company computes its expected volatility assumption based on a blended volatility ( 50% historical volatility and 50% implied volatility from traded options on the Company's common stock). The selection of a blended volatility assumption was based upon the Company's assessment that a blended volatility is more representative of the Company's future stock price trend as it weighs the historical volatility with the future implied volatility. (ii) Expected life of the option award - Represents the weighted-average period that the stock options are expected to remain outstanding. The Company’s computation of expected life utilizes the simplified method in accordance with Staff Accounting Bulletin No. 110 ("SAB 110") due to the lack of sufficient historical exercise data to provide a reasonable basis upon which to estimate expected term. The mid-point between the vesting date and the expiration date is used as the expected term under this method. (iii) Expected dividend yield - Assumption is based on the Company's history of not paying dividends and no future expectations of dividend payouts. (iv) Risk-free interest rate - Based on the U.S. Treasury yield curve in effect at the time of grant with maturities approximating the grant’s expected life. The following table summarizes the weighted-average assumptions used in estimating the grant-date fair value of stock options in the periods indicated: Three Months Ended Nine Months Ended September 26, 2015 September 27, September 26, 2015 September 27, Expected volatility N/A N/A 52% 54% Expected life (years) N/A N/A 6.25 6.15 Expected dividend yield N/A N/A — — Risk-free interest rate N/A N/A 1.56% 1.91% Modification of Stock Awards In February 2013, the Company entered into a Transition and Separation Agreement ("Agreement") with Roger Weingarth, the Company's former Executive Vice President and Chief Operating Officer. Under the Agreement, Mr. Weingarth transitioned to the role of advisor to the Chief Executive Officer of the Company effective as of April 1, 2013, and terminated his employment with the Company on March 31, 2014 ("Termination Date"). Upon his termination, the Agreement provided for, among other things, the acceleration of the vesting of his unvested stock options, RSAs and RSUs held by him as of the Termination Date. In accordance with ASC Topic 718, total fair value of the accelerated stock awards after the modification was $0.6 million , which was recognized on a straight-line basis over the remaining service period through the Termination Date. During the nine months ended September 27, 2014 , $0.1 million of the total fair value has been recognized in general and administrative expenses. There was no expense recognized during the three months ended September 27, 2014 as the total fair value of the accelerated stock awards has been fully amortized as of the end of the first quarter of fiscal 2014. 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. During the three months ended September 26, 2015 , the Company repurchased 1,011,826 shares of common stock for $7.7 million at an average price of $7.66 per share. During the nine months ended September 26, 2015 , the Company repurchased 1,446,826 shares of common stock for $11.1 million at an average price of $7.69 per share. As of September 26, 2015 , approximately $28.9 million remained available for repurchase of the Company's common stock pursuant to this stock repurchase program. 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. The repurchase program may be suspended, terminated or modified at any time. The program does not oblige the Company to purchase any particular number of shares.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	9 Months Ended
	Sep. 26, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands). Three Months Ended September 26, 2015 September 27, 2014 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 $ (22 ) $ 157 $ 135 $ (25 ) $ 184 $ 159 Other comprehensive income (loss) before reclassification adjustments 30 (196 ) (166 ) (12 ) (7 ) (19 ) Reclassification adjustment for realized gains on marketable securities included in net income (loss) — — — (1 ) — (1 ) Other comprehensive income (loss) 30 (196 ) (166 ) (13 ) (7 ) (20 ) Balance at end of period $ 8 $ (39 ) $ (31 ) $ (38 ) $ 177 $ 139 Nine Months Ended September 26, 2015 September 27, 2014 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 $ (58 ) $ 138 $ 80 $ — $ 190 $ 190 Other comprehensive income (loss) before reclassification adjustments 66 (177 ) (111 ) (37 ) (13 ) (50 ) Reclassification adjustment for realized gains on marketable securities included in net income (loss) — — — (1 ) — (1 ) Other comprehensive income (loss) 66 (177 ) (111 ) (38 ) (13 ) (51 ) Balance at end of period $ 8 $ (39 ) $ (31 ) $ (38 ) $ 177 $ 139 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 our Condensed Consolidated Statements of Comprehensive Income (Loss).

Credit Facility

Credit Facility	9 Months Ended
	Sep. 26, 2015
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 our Condensed Consolidated Balance Sheet as of December 31, 2014. On July 29, 2013 , the Company entered into a credit agreement with Bank of America, N.A. 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 July 29, 2016 , but may be extended up to two times (each extension for an additional one-year period) upon mutual agreement of the Company and the Lenders. The credit facility is secured by substantially all of our assets, including our 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 (customarily defined). Interest on the revolving facility is due quarterly, and any outstanding interest and principal is due on the maturity date of the revolving facility. The Company is required to repay principal on a term loan in twenty equal quarterly payments from the date the Company enters into a term loan, and all outstanding principal and accrued interest is due on the revolving facility maturity date. Swingline loans must be repaid on the earlier of (i) ten business days after a loan is made and (ii) the revolving facility maturity date. The Company is also required to pay commitment fees of 0.25% per year on any unused portions of this facility. The credit facility includes affirmative and negative covenants applicable to the Company that are typical for credit facilities of this type. Furthermore, the credit agreement requires us to maintain certain financial covenants, including a maximum consolidated leverage ratio, and a minimum consolidated liquidity ratio of cash, cash equivalents and accounts receivable to consolidated funded indebtedness. As of September 26, 2015 , the Company was in compliance with these requirements. The credit facility also includes customary events of default, the occurrence and continuation of which would provide the Lenders with the right to demand immediate repayment of any principal and unpaid interest under the credit facility, and to exercise remedies against us and the collateral securing the loans under the credit facility. As of September 26, 2015 , the Company had no outstanding letters of credit or borrowings under the credit facility. The Company incurred $0.3 million of debt issuance costs that were directly attributable to the issuance of this credit facility. These costs will be amortized over three years starting from the effective date of the credit facility and are included within "other assets" in our Condensed Consolidated Balance Sheets. As of September 26, 2015 , unamortized debt issuance costs were $0.1 million .

Income Taxes

Income Taxes	9 Months Ended
	Sep. 26, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Provision for income taxes $ 185 $ 115 $ 378 $ 328 Effective tax rate 16.7 % (3.1 )% (2.3 )% (1.9 )% The income tax provision for the three and nine months ended September 26, 2015 consisted primarily of foreign income taxes. The effective tax rate for the three and nine months ended September 26, 2015 was determined using an estimated annual effective tax rate adjusted for discrete items, if any, that occurred during the period. The Company’s effective tax rate for the three and nine months ended September 26, 2015 is impacted by the change in valuation allowances against deferred tax assets and foreign income tax expense . The income tax provision for the three and nine months ended September 27, 2014 primarily consisted of state and foreign income taxes. The effective tax rate for the three and nine months ended September 27, 2014 was determined by estimating the tax provision using the discrete method provided in ASC Topic740. The discrete method was used because of unpredictable trends in the Company’s U.S. net income or loss position. The Company’s effective tax rate for the three and nine months ended September 27, 2014 was impacted by the change in valuation allowances against deferred tax assets and state income tax expense . ASC Topic 740, Income Taxes, ("ASC Topic 740"), provides for the recognition of deferred tax assets if realization of such assets is more likely than not. The Company has established and continues to maintain a full valuation allowance against its net deferred tax assets, with the exception of certain foreign deferred tax assets, as the Company does not believe that realization of those assets is more likely than not . Our effective tax rate may be subject to fluctuation during the year as new information is obtained, which may affect the assumptions used to estimate the annual effective tax rate, including factors such as the mix of forecasted pre-tax earnings in the various jurisdictions in which we operate, valuation allowances against deferred tax assets, the recognition or de-recognition of tax benefits related to uncertain tax positions, and changes in or the interpretation of tax laws in jurisdictions where we conduct business .

Significant Accounting Polici18

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 26, 2015
Accounting Policies [Abstract]
Legal Fees	Legal Fees The Company incurs legal expenses related to disputes, litigation and other legal actions in the ordinary course of business. Legal fees, including those legal defense costs expected to be incurred in connection with a loss contingency, are expensed as incurred in the period that the related services are received. In the event the Company has insurance coverage for legal defense costs incurred and the likelihood of reimbursement is assured, legal defense costs recognized in a period are reduced by the amount recoverable from the insurance. A receivable is recognized for the portion of legal costs recoverable under the insurance at the time such legal costs are incurred and accrued.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("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 potential impact on its financial statements from adopting this new guidance.

Cash, Cash Equivalents and Ma19

Cash, Cash Equivalents and Marketable Securities (Tables)	9 Months Ended
	Sep. 26, 2015
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash, cash equivalents and marketable securities consisted of the following (in thousands): September 26, December 31, Cash and cash equivalents: Cash $ 19,675 $ 17,866 Money market funds 16,519 30,963 Total cash and cash equivalents 36,194 48,829 Marketable securities: Corporate debt securities 44,802 61,050 U.S. government agency securities 10,564 — Commercial paper 2,293 1,800 Total marketable securities 57,659 62,850 Total cash, cash equivalents and marketable securities $ 93,853 $ 111,679
Amortized cost and fair value of marketable securities	As of September 26, 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 $ 44,796 $ 16 $ (10 ) $ 44,802 U.S. government agency securities 10,562 2 — 10,564 Commercial paper 2,293 — — 2,293 Total marketable securities $ 57,651 $ 18 $ (10 ) $ 57,659 As of December 31, 2014 , 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 $ 61,108 $ 1 $ (59 ) $ 61,050 Commercial paper 1,800 — — 1,800 Total marketable securities $ 62,908 $ 1 $ (59 ) $ 62,850
Amortized cost and fair value of marketable securities by contractual maturity	As of September 26, 2015 , 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 $ 37,139 $ 37,139 Due in 1-2 years 20,512 20,520 Total marketable securities $ 57,651 $ 57,659

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 26, 2015
Fair Value Disclosures [Abstract]
Summary of fair values of financial assets	The following table sets forth the Company's financial assets measured at fair value on a recurring basis as of September 26, 2015 and December 31, 2014 , based on the three-tier fair value hierarchy (in thousands): As of September 26, 2015 Level 1 Level 2 Total Money market funds $ 16,519 $ — $ 16,519 Corporate debt securities — 44,802 44,802 U.S. government agency securities — 10,564 10,564 Commercial paper — 2,293 2,293 Total $ 16,519 $ 57,659 $ 74,178 As of December 31, 2014 Level 1 Level 2 Total Money market funds $ 30,963 $ — $ 30,963 Corporate debt securities — 61,050 61,050 Commercial paper — 1,800 1,800 Total $ 30,963 $ 62,850 $ 93,813

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 26, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of intangible assets	Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of September 26, 2015 and December 31, 2014 are disclosed in the following table (in thousands): September 26, 2015 December 31, 2014 Gross Carrying Amount Accumulated Amortization Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (61,958 ) $ 7,006 $ 68,964 $ (55,694 ) $ 13,270 Customer relationships 54,740 (50,487 ) 4,253 54,740 (42,831 ) 11,909 Total intangible assets, excluding goodwill $ 123,704 $ (112,445 ) $ 11,259 $ 123,704 $ (98,525 ) $ 25,179
Expected future amortization	As of September 26, 2015 , expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense Remainder of 2015 $ 4,640 2016 5,805 2017 814 Total $ 11,259

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	9 Months Ended
	Sep. 26, 2015
Balance Sheet Related Disclosures [Abstract]
Summary of accounts receivable, net	Accounts receivable, net consisted of the following (in thousands): September 26, December 31, Accounts receivable $ 49,132 $ 31,493 Allowance for doubtful accounts (405 ) (241 ) Product return reserve (539 ) (508 ) Accounts receivable, net $ 48,188 $ 30,744
Summary of inventory	Inventory consisted of the following (in thousands): September 26, December 31, Raw materials $ 2,259 $ 3,180 Finished goods 41,510 43,573 Total inventory $ 43,769 $ 46,753
Summary of property and equipment, net	Property and equipment, net consisted of the following (in thousands): September 26, December 31, Test equipment $ 40,501 $ 40,766 Computer equipment and software 28,061 30,355 Furniture and fixtures 1,835 1,852 Leasehold improvements 6,553 6,550 Total 76,950 79,523 Accumulated depreciation and amortization (58,466 ) (59,379 ) Property and equipment, net $ 18,484 $ 20,144
Summary of accrued liabilities	Accrued liabilities consisted of the following (in thousands): September 26, December 31, Accrued compensation and related benefits $ 16,547 $ 15,782 Accrued warranty 8,984 9,553 Accrued professional and consulting fees 3,016 5,860 Accrued customer rebates 1,327 851 Accrued excess and obsolete inventory at contract manufacturers 1,237 888 Accrued business travel expenses 1,024 1,414 Sales and use tax payable 1,000 397 Advance customer payments 699 364 Accrued business events 543 — Accrued rent 385 412 Accrued freight 277 303 Income taxes payable 245 269 Accrued other 2,996 3,350 Total accrued liabilities $ 38,280 $ 39,443
Summary of deferred revenue	Deferred revenue consisted of the following (in thousands): September 26, December 31, 2014 Product and services - current $ 8,463 $ 9,753 Extended warranty - current 2,951 2,969 Extended warranty - non-current 19,358 19,211 Product and services - non-current 32 182 Total deferred revenue $ 30,804 $ 32,115

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 26, 2015
Commitments and Contingencies Disclosure [Abstract]
Product warranty activities	Changes in the Company’s warranty reserve were as follows (in thousands): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Balance at beginning of period $ 9,325 $ 10,638 $ 9,553 $ 10,856 Warranty charged to cost of revenue 781 839 2,929 3,364 Utilization of warranty (722 ) (452 ) (3,098 ) (3,195 ) Adjustments to pre-existing warranty (400 ) (250 ) (400 ) (250 ) Balance at end of period $ 8,984 $ 10,775 $ 8,984 $ 10,775

Net Income (Loss) per Common 24

Net Income (Loss) per Common Share (Tables)	9 Months Ended
	Sep. 26, 2015
Earnings Per Share [Abstract]
Schedule of net loss per share	The following table sets forth the computation of basic and diluted net income (loss) per common share for the periods indicated (in thousands, except per share data): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Numerator: Net income (loss) $ 922 $ (3,848 ) $ (16,787 ) $ (17,826 ) Denominator: Weighted-average common shares outstanding used to compute basic net income (loss) per share 51,756 51,048 51,814 50,635 Effect of dilutive common stock equivalents 260 — — — Weighted-average common shares outstanding used to compute diluted net income (loss) per share 52,016 51,048 51,814 50,635 Basic net income (loss) per common share $ 0.02 $ (0.08 ) $ (0.32 ) $ (0.35 ) Diluted net income (loss) per common share $ 0.02 $ (0.08 ) $ (0.32 ) $ (0.35 ) Potentially dilutive shares, weighted average 5,244 5,262 6,062 5,011

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 26, 2015
Stockholders' Equity Note [Abstract]
Weighted-average assumptions used to estimate the fair value of stock options	The following table summarizes the weighted-average assumptions used in estimating the grant-date fair value of stock options in the periods indicated: Three Months Ended Nine Months Ended September 26, 2015 September 27, September 26, 2015 September 27, Expected volatility N/A N/A 52% 54% Expected life (years) N/A N/A 6.25 6.15 Expected dividend yield N/A N/A — — Risk-free interest rate N/A N/A 1.56% 1.91%

Accumulated Other Comprehensi26

Accumulated Other Comprehensive Income (Loss) (Tables)	9 Months Ended
	Sep. 26, 2015
Equity [Abstract]
Accumulated other comprehensive income details	The table below summarizes the changes in accumulated other comprehensive income (loss) by component for the periods indicated (in thousands). Three Months Ended September 26, 2015 September 27, 2014 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 $ (22 ) $ 157 $ 135 $ (25 ) $ 184 $ 159 Other comprehensive income (loss) before reclassification adjustments 30 (196 ) (166 ) (12 ) (7 ) (19 ) Reclassification adjustment for realized gains on marketable securities included in net income (loss) — — — (1 ) — (1 ) Other comprehensive income (loss) 30 (196 ) (166 ) (13 ) (7 ) (20 ) Balance at end of period $ 8 $ (39 ) $ (31 ) $ (38 ) $ 177 $ 139 Nine Months Ended September 26, 2015 September 27, 2014 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 $ (58 ) $ 138 $ 80 $ — $ 190 $ 190 Other comprehensive income (loss) before reclassification adjustments 66 (177 ) (111 ) (37 ) (13 ) (50 ) Reclassification adjustment for realized gains on marketable securities included in net income (loss) — — — (1 ) — (1 ) Other comprehensive income (loss) 66 (177 ) (111 ) (38 ) (13 ) (51 ) Balance at end of period $ 8 $ (39 ) $ (31 ) $ (38 ) $ 177 $ 139

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 26, 2015
Income Tax Disclosure [Abstract]
Schedule of income taxes	The following table presents the provision for income taxes from continuing operations and the effective tax rates for the periods indicated (in thousands, except percentages): Three Months Ended Nine Months Ended September 26, September 27, September 26, September 27, Provision for income taxes $ 185 $ 115 $ 378 $ 328 Effective tax rate 16.7 % (3.1 )% (2.3 )% (1.9 )%

Cash, Cash Equivalents and Ma28

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014	Sep. 27, 2014	Dec. 31, 2013
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 36,194	$ 48,829	$ 39,399	$ 82,747
Marketable securities	57,659	62,850
Total cash, cash equivalents and marketable securities	93,853	111,679
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities	44,802	61,050
U.S. government agency securities
Cash and Cash Equivalents [Line Items]
Marketable securities	10,564	0
Commercial paper
Cash and Cash Equivalents [Line Items]
Marketable securities	2,293	1,800
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	19,675	17,866
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 16,519	$ 30,963

Cash, Cash Equivalents and Ma29

Cash, Cash Equivalents and Marketable Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 57,651	$ 62,908
Gross Unrealized Gains	18	1
Gross Unrealized Losses	(10)	(59)
Fair Value	57,659	62,850
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	44,796	61,108
Gross Unrealized Gains	16	1
Gross Unrealized Losses	(10)	(59)
Fair Value	44,802	61,050
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,562
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Fair Value	10,564	0
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,293	1,800
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 2,293	$ 1,800

Cash, Cash Equivalents and Ma30

Cash, Cash Equivalents and Marketable Securities - Contractual Maturity (Details) $ in Thousands	Sep. 26, 2015USD ($)
Cash and Cash Equivalents [Abstract]
Marketable securities due in 1 year or less, amortized cost	$ 37,139
Marketable securities due in 1-2 years, amortized cost	20,512
Marketable securities, amortized cost	57,651
Marketable securities due in 1 year or less, fair value	37,139
Marketable securities due in 1-2 years, fair value	20,520
Marketable securities, fair value	$ 57,659

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	$ 57,659	$ 62,850
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	74,178	93,813
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	16,519	30,963
Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total	57,659	62,850
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	44,802	61,050
Corporate debt securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	44,802	61,050
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	44,802	61,050
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,564	0
U.S. government agency securities | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	10,564
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
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	10,564
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2,293	1,800
Commercial paper | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Marketable securities	2,293	1,800
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	2,293	1,800
Money market funds | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	16,519	30,963
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	16,519	30,963
Money market funds | Fair Value, Measurements, Recurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 0	$ 0

Goodwill and Intangible Asset32

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 123,704	$ 123,704
Accumulated Amortization	(112,445)	(98,525)
Net	11,259	25,179
Core developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	68,964	68,964
Accumulated Amortization	(61,958)	(55,694)
Net	7,006	13,270
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	54,740	54,740
Accumulated Amortization	(50,487)	(42,831)
Net	$ 4,253	$ 11,909

Goodwill and Intangible Asset33

Goodwill and Intangible Assets - Expected Future Amortization (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Expected future amortization
Remainder of 2015	$ 4,640
2,016	5,805
2,017	814
Net	$ 11,259	$ 25,179

Goodwill and Intangible Asset34

Goodwill and Intangible Assets - Textual (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill, impairment loss			$ 0
Amortization expense	$ 4,600,000	$ 4,600,000	$ 13,920,000	$ 13,921,000

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Summary of accounts receivable, net
Accounts receivable	$ 49,132	$ 31,493
Allowance for doubtful accounts	(405)	(241)
Product return reserve	(539)	(508)
Accounts receivable, net	$ 48,188	$ 30,744

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Summary of inventory, net
Raw materials	$ 2,259	$ 3,180
Finished goods	41,510	43,573
Total inventory	$ 43,769	$ 46,753

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Summary of property and equipment, net
Property and equipment, gross	$ 76,950	$ 79,523
Accumulated depreciation and amortization	(58,466)	(59,379)
Property and equipment, net	18,484	20,144
Test equipment
Summary of property and equipment, net
Property and equipment, gross	40,501	40,766
Computer equipment and software
Summary of property and equipment, net
Property and equipment, gross	28,061	30,355
Furniture and fixtures
Summary of property and equipment, net
Property and equipment, gross	1,835	1,852
Leasehold improvements
Summary of property and equipment, net
Property and equipment, gross	$ 6,553	$ 6,550

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Summary of accrued liabilities
Accrued compensation and related benefits	$ 16,547	$ 15,782
Accrued warranty	8,984	9,553
Accrued professional and consulting fees	3,016	5,860
Accrued customer rebates	1,327	851
Accrued excess and obsolete inventory at contract manufacturers	1,237	888
Accrued business travel expenses	1,024	1,414
Sales and use tax payable	1,000	397
Advance customer payments	699	364
Accrued business events	543	0
Accrued rent	385	412
Accrued freight	277	303
Income taxes payable	245	269
Accrued other	2,996	3,350
Total accrued liabilities	$ 38,280	$ 39,443

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 26, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 11,414	$ 12,722
Deferred revenue, noncurrent	19,390	19,393
Deferred revenue	30,804	32,115
Product and services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	8,463	9,753
Deferred revenue, noncurrent	32	182
Extended warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	2,951	2,969
Deferred revenue, noncurrent	$ 19,358	$ 19,211

Commitments and Contingencies -

Commitments and Contingencies - Textual (Details) $ / shares in Units, $ in Millions	Jan. 06, 2012USD ($)	Sep. 16, 2010Subsidiary	Sep. 26, 2015	Feb. 22, 2011$ / sharesshares
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
Occam Acquisition | Occam Shareholders Versus Occam and Occam Board of Directors
Commitments and Contingencies [Line Items]
Number of shares held by plaintiffs | shares				15,147,085
Occam Acquisition | Occam Shareholders Versus Occam and Occam Board of Directors | Minimum
Commitments and Contingencies [Line Items]
Share price, estimated in excess of merger consideration				$ 7.77
Occam Acquisition | Occam Shareholders Versus Occam and Occam Board of Directors | Maximum
Commitments and Contingencies [Line Items]
Share price, estimated in excess of merger consideration				$ 9.65

Commitments and Contingencies41

Commitments and Contingencies - Product Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Product warranty activities [Roll Forward]
Balance at beginning of period	$ 9,325	$ 10,638	$ 9,553	$ 10,856
Warranty charged to cost of revenue	781	839	2,929	3,364
Utilization of warranty	(722)	(452)	(3,098)	(3,195)
Adjustments to pre-existing warranty	(400)	(250)	(400)	(250)
Balance at end of period	$ 8,984	$ 10,775	$ 8,984	$ 10,775

Net Income (Loss) per Common 42

Net Income (Loss) per Common Share - Basic and Diluted Shares Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Numerator:
Net income (loss)	$ 922	$ (3,848)	$ (16,787)	$ (17,826)
Denominator:
Weighted-average common shares outstanding used to compute basic net income (loss) per share (shares)	51,756	51,048	51,814	50,635
Effect of dilutive common stock equivalents (shares)	260	0	0	0
Weighted-average common shares outstanding used to compute diluted net income (loss) per share (shares)	52,016	51,048	51,814	50,635
Basic net income (loss) per common share (in dollars per share)	$ 0.02	$ (0.08)	$ (0.32)	$ (0.35)
Diluted net income (loss) per common share (in dollars per share)	$ 0.02	$ (0.08)	$ (0.32)	$ (0.35)
Potentially dilutive shares, weighted average (in shares)	5,244	5,262	6,062	5,011

Stockholders' Equity - Weighted

Stockholders' Equity - Weighted-average Assumptions Used to Estimate Fair Value of Stock Options (Details) - Stock Options	9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014
Weighted-average assumptions used to estimate fair value of stock options
Expected volatility	52.00%	54.00%
Expected life (years)	6 years 3 months	6 years 1 month 24 days
Expected dividend yield	0.00%	0.00%
Risk free interest rate	1.56%	1.91%

Stockholders' Equity - Textual

Stockholders' Equity - Textual (Details)	3 Months Ended		9 Months Ended
	Sep. 26, 2015USD ($)Plan$ / sharesshares	Sep. 27, 2014USD ($)	Sep. 26, 2015USD ($)Plan$ / sharesshares	Sep. 27, 2014USD ($)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | Plan	3		3
Stock options granted	0		200,000
Weighted-average grant date fair value | $ / shares			$ 4.56
Stock options exercised	6,301		94,987
Weighted-average exercise price per share, stock options | $ / shares	$ 5.49		$ 6.58
Unrecognized stock-based compensation expense, stock options | $	$ 8,000,000		$ 8,000,000
Weighted-average amortization period			2 years 11 months
Taxes paid for awards vested under equity incentive plans | $			$ 2,093,000	$ 2,505,000
Weight of historical volatility			50.00%
Weight of implied volatility			50.00%
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period			2 years 9 months
Awards granted	165,300		1,521,761
Weighted-average grant date fair value per share | $ / shares	$ 7.48		$ 8.57
Awards vested	110,637		408,471
Taxes paid for awards vested under equity incentive plans | $	$ 500,000		$ 1,500,000
Unrecognized stock-based compensation expense | $	$ 15,400,000		$ 15,400,000
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted	0		0
Awards vested			0
Taxes paid for awards vested under equity incentive plans | $	$ 129,000		$ 160,000
Shares outstanding	0		0
Unrecognized stock-based compensation expense | $	$ 0		$ 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		$ 200,000
ESPP, maximum employee payroll deduction percentage	15.00%		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	1,469,648		1,469,648
Shares issued under the ESPP	0		421,335
Performance Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average amortization period			5 months 20 days
Awards granted	0		0
Taxes paid for awards vested under equity incentive plans | $			$ 500,000
Unrecognized stock-based compensation expense | $	$ 300,000		$ 300,000
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	0		147,916
Performance Restricted Stock Units | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period			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 of accelerated stock awards | $			$ 600,000
Fair value recognized for accelerated stock awards | $		$ 0		$ 100,000
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			92,359

Stockholders' Equity - Stock Re

Stockholders' Equity - Stock Repurchase (Details) - Common Stock - USD ($)	3 Months Ended	9 Months Ended
	Sep. 26, 2015	Sep. 26, 2015	Apr. 26, 2015
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 40,000,000
Number of shares repurchased	1,011,826	1,446,826
Shares repurchased, value	$ 7,700,000	$ 11,100,000
Average price per share	$ 7.66	$ 7.69
Remaining authorized repurchase amount	$ 28,900,000	$ 28,900,000

Accumulated Other Comprehensi46

Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	$ 135	$ 159	$ 80	$ 190
Other comprehensive income (loss) before reclassification adjustments	(166)	(19)	(111)	(50)
Reclassification adjustment for realized gains on marketable securities included in net income (loss)	0	(1)	0	(1)
Total other comprehensive income (loss), net of tax	(166)	(20)	(111)	(51)
Balance at end of period	(31)	139	(31)	139
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	(22)	(25)	(58)	0
Other comprehensive income (loss) before reclassification adjustments	30	(12)	66	(37)
Reclassification adjustment for realized gains on marketable securities included in net income (loss)	0	(1)	0	(1)
Total other comprehensive income (loss), net of tax	30	(13)	66	(38)
Balance at end of period	8	(38)	8	(38)
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance at beginning of period	157	184	138	190
Other comprehensive income (loss) before reclassification adjustments	(196)	(7)	(177)	(13)
Reclassification adjustment for realized gains on marketable securities included in net income (loss)	0	0	0	0
Total other comprehensive income (loss), net of tax	(196)	(7)	(177)	(13)
Balance at end of period	$ (39)	$ 177	$ (39)	$ 177

Credit Facility - Textual (Deta

Credit Facility - Textual (Details)	Jul. 29, 2013USD ($)extension	Jun. 30, 2013USD ($)	Mar. 28, 2015USD ($)	Sep. 26, 2015USD ($)payment	Sep. 27, 2014USD ($)
Credit Facility [Line Items]
Maximum borrowing capacity	$ 50,000,000
Maturity date	Jul. 29, 2016
Restricted cash released			$ (300,000)	$ (295,000)	$ 0
Initiation date	Jul. 29, 2013
Number of one-year period extensions | extension	2
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 letters of credit				$ 0
Borrowings under the credit facility				0
Debt issuance costs incurred	$ 300,000
Period of amortization of debt issuance costs	3 years
Unamortized debt issuance costs				$ 100,000
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		9 Months Ended
	Sep. 26, 2015	Sep. 27, 2014	Sep. 26, 2015	Sep. 27, 2014
Income Tax Disclosure [Abstract]
Provision for income taxes	$ 185	$ 115	$ 378	$ 328
Effective tax rate	16.70%	(3.10%)	(2.30%)	(1.90%)