Calix (CALX) 10-K 26 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Feb. 18, 2016	Jun. 27, 2015
Document and Entity Information [Abstract]
Entity Registrant Name	CALIX, INC
Entity Central Index Key	1,406,666
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Amendment Flag	false
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Trading Symbol	calx
Entity Common Stock, Shares Outstanding		48,452,157
Entity Public Float			$ 358

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current Assets:
Cash and cash equivalents	$ 23,626	$ 48,829
Marketable securities	49,964	62,850
Restricted cash	0	295
Accounts receivable, net	47,155	30,744
Inventory	47,667	46,753
Deferred cost of revenue	4,918	5,080
Prepaid expenses and other current assets	9,470	12,936
Total current assets	182,800	207,487
Property and equipment, net	17,149	20,144
Goodwill	116,175	116,175
Intangible assets, net	6,618	25,179
Other assets	1,144	1,236
Total assets	323,886	370,221
Current liabilities:
Accounts payable	19,603	23,629
Accrued liabilities	35,512	39,443
Deferred revenue	12,124	12,722
Total current liabilities	67,239	75,794
Long-term portion of deferred revenue	19,569	19,393
Other long-term liabilities	1,293	2,443
Total liabilities	$ 88,101	$ 97,630
Commitments and contingencies (See Note 6)
Stockholders’ equity:
Preferred stock, $0.025 par value; 5,000,000 shares authorized; no shares issued and outstanding as of December 31, 2015 and December 31, 2014	$ 0	$ 0
Common stock, $0.025 par value; 100,000,000 shares authorized; 53,049,781 shares issued and 49,509,251 shares outstanding as of December 31, 2015, and 51,628,257 shares issued and outstanding as of December 31, 2014	1,326	1,291
Additional paid-in capital	818,754	801,810
Accumulated other comprehensive income (loss)	(195)	80
Accumulated deficit	(556,923)	(530,590)
Treasury stock, 3,540,530 shares as of December 31, 2015	(27,177)	0
Total stockholders’ equity	235,785	272,591
Total liabilities and stockholders’ equity	$ 323,886	$ 370,221

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.025	$ 0.025
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.025	$ 0.025
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	53,049,781	51,628,257
Common stock, shares outstanding	49,509,251	51,628,257
Treasury Stock, Shares	3,540,530	0

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue		$ 407,463	$ 401,227	$ 382,618
Cost of revenue:
Products and services	[1]	208,681	215,085	203,191
Amortization of intangible assets		8,353	8,353	8,353
Total cost of revenue		217,034	223,438	211,544
Gross profit		190,429	177,789	171,074
Operating expenses:
Research and development	[1]	89,714	80,311	79,299
Sales and marketing	[1]	78,563	76,283	68,075
General and administrative	[1]	38,454	31,371	31,945
Amortization of intangible assets		10,208	10,208	10,208
Total operating expenses		216,939	198,173	189,527
Loss from operations		(26,510)	(20,384)	(18,453)
Interest and other income (expense), net:
Interest income		1,285	729	7
Interest expense		(1,144)	(806)	(167)
Utilization of inventory credit		0	0	1,651
Other income (expense), net		571	228	(317)
Total interest and other income (expense), net		712	151	1,174
Loss before provision for (benefit from) income taxes		(25,798)	(20,233)	(17,279)
Provision for (benefit from) income taxes		535	581	(14)
Net loss		$ (26,333)	$ (20,814)	$ (17,265)
Net loss per common share:
Basic and diluted (in dollars per share)		$ (0.51)	$ (0.41)	$ (0.35)
Weighted-average number of shares used to compute net loss per common share:
Basic and diluted (in shares)		51,489	50,808	49,419
Other comprehensive income (loss), net of tax:
Unrealized losses on available-for-sale marketable securities adjustment, net		$ (36)	$ (58)	$ 0
Foreign currency translation adjustments, net		(239)	(52)	58
Total other comprehensive income (loss), net of tax		(275)	(110)	58
Comprehensive loss		(26,608)	(20,924)	(17,207)
Stock based compensation		13,805	16,017	19,921
Cost of revenue
Other comprehensive income (loss), net of tax:
Stock based compensation		709	1,120	1,468
Research and development
Other comprehensive income (loss), net of tax:
Stock based compensation		4,797	5,056	4,896
Sales and marketing
Other comprehensive income (loss), net of tax:
Stock based compensation		4,712	5,601	5,577
General and administrative
Other comprehensive income (loss), net of tax:
Stock based compensation		$ 3,587	$ 4,240	$ 7,980
[1]	Includes stock-based compensation as follows (in thousands): Years Ended December 31, 2014, 2013, and 2012;Cost of revenue: $709, $1,120, $1,468;Research and development: $4,797, $5,056, $4,896;Sales and marketing: $4,712, $5,601, $5,577;General administrative: $3,587, $4,240, $7,980;Total: $13,805, $16,017, $19,921.

Consolidated Statements of Stoc

Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Treasury Stock
Beginning Balance, shares at Dec. 31, 2012		48,899,000
Beginning Balance at Dec. 31, 2012	$ 269,075	$ 1,222	$ 760,232	$ 132	$ (492,511)	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	19,921		19,921
Exercise of stock options and warrants, shares		160,000
Exercise of stock options and warrants	747	$ 4	743
issuance of vested restricted stock units, net of taxes withheld, shares		529,000
Issuance of vested restricted stock units, net of taxes withheld	(3,031)	$ 14	(3,045)
Stock issued under employee stock purchase plan, shares		686,000
Stock issued under employee stock purchase plan	4,828	$ 17	4,811
Shares withheld for taxes for vested restricted stock awards, shares		(34,000)
Shares withheld for taxes for vested restricted stock awards	(410)	$ (1)	(409)
Restricted stock awards forfeited, shares		(15,000)
Restricted stock awards forfeited	0	$ 0	0
Net loss	(17,265)				(17,265)
Other comprehensive income (loss)	58			58
Ending Balance, shares at Dec. 31, 2013		50,225,000
Ending Balance at Dec. 31, 2013	273,923	$ 1,256	782,253	190	(509,776)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	16,017		16,017
Exercise of stock options and warrants, shares		224,000
Exercise of stock options and warrants	1,668	$ 6	1,662
Issuance of vested performance restricted stock units, net of taxes withheld, shares		99,000
Issuance of vested performance restricted stock units, net of taxes withheld	(533)	$ 2	(535)
issuance of vested restricted stock units, net of taxes withheld, shares		449,000
Issuance of vested restricted stock units, net of taxes withheld	(1,840)	$ 11	(1,851)
Stock issued under employee stock purchase plan, shares		683,000
Stock issued under employee stock purchase plan	4,627	$ 17	4,610
Shares withheld for taxes for vested restricted stock awards, shares		(42,000)
Shares withheld for taxes for vested restricted stock awards	(347)	$ (1)	(346)
Restricted stock awards forfeited, shares		(10,000)
Restricted stock awards forfeited	0	$ 0	0
Net loss	(20,814)				(20,814)
Other comprehensive income (loss)	$ (110)			(110)
Ending Balance, shares at Dec. 31, 2014	51,628,257	51,628,000
Ending Balance at Dec. 31, 2014	$ 272,591	$ 1,291	801,810	80	(530,590)	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	$ 13,805		13,805
Exercise of stock options and warrants, shares	97,000	97,000
Exercise of stock options and warrants	$ 638	$ 2	636
Issuance of vested performance restricted stock units, net of taxes withheld, shares		92,000
Issuance of vested performance restricted stock units, net of taxes withheld	(471)	$ 2	(473)
issuance of vested restricted stock units, net of taxes withheld, shares		491,000
Issuance of vested restricted stock units, net of taxes withheld	$ (1,721)	$ 12	(1,733)
Stock issued under employee stock purchase plan, shares	761,844	762,000
Stock issued under employee stock purchase plan	$ 4,888	$ 19	4,869
Shares withheld for taxes for vested restricted stock awards, shares		(20,000)
Shares withheld for taxes for vested restricted stock awards	(160)	$ 0	(160)
Net loss	(26,333)				(26,333)
Other comprehensive income (loss)	(275)			(275)
Repurchases of common stock, shares		(3,541,000)
Repurchases of common stock	$ (27,177)					(27,177)
Ending Balance, shares at Dec. 31, 2015	49,509,251	49,509,000
Ending Balance at Dec. 31, 2015	$ 235,785	$ 1,326	$ 818,754	$ (195)	$ (556,923)	$ (27,177)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities:
Net loss	$ (26,333)	$ (20,814)	$ (17,265)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	10,262	9,263	10,181
Loss on retirement of property and equipment	24	50	569
Amortization of intangible assets	18,561	18,561	18,561
Amortization of premiums relating to available-for-sale securities	907	574	0
Gain on sale of available-for-sale securities	0	(1)	0
Stock-based compensation	13,805	16,017	19,921
Utilization of inventory credit	0	0	(1,651)
Changes in operating assets and liabilities:
Restricted cash	295	0	(295)
Accounts receivable, net	(16,411)	12,776	15,999
Inventory	(915)	4,319	(6,138)
Deferred cost of revenue	162	15,996	1
Prepaid expenses and other assets	2,889	(5,908)	535
Accounts payable	(4,021)	467	6,359
Accrued liabilities	(3,781)	7,440	(4,217)
Deferred revenue	(422)	(21,178)	(1,804)
Other long-term liabilities	(363)	513	62
Net cash provided by (used in) operating activities	(5,341)	38,075	40,818
Investing activities:
Purchases of property and equipment	(7,278)	(11,961)	(6,987)
Purchases of marketable securities	(60,002)	(67,698)	0
Sales of marketable securities	0	615	0
Maturities of marketable securities	71,945	3,600	0
Net cash provided by (used in) investing activities	4,665	(75,444)	(6,987)
Financing activities:
Proceeds from exercise of stock options	638	1,668	747
Proceeds from employee stock purchase plan	4,888	4,627	4,828
Payments for repurchases of common stock	(27,177)	0	0
Taxes paid for awards vested under equity incentive plans	(2,352)	(2,720)	(3,441)
Payments for debt issuance costs	(138)	0	(316)
Net cash provided by (used in) financing activities	(24,141)	3,575	1,818
Effect of exchange rate changes on cash and cash equivalents	(386)	(124)	103
Net increase (decrease) in cash and cash equivalents	(25,203)	(33,918)	35,752
Cash and cash equivalents at beginning of period	48,829	82,747	46,995
Cash and cash equivalents at end of period	23,626	48,829	82,747
Supplemental disclosures of cash flow information
Interest paid	127	159	57
Income taxes paid	483	72	96
Non-cash financing and investing activities
Property and equipment acquired using credits from Ericsson Inc.	$ 0	$ 0	$ 125

Description of Business and Sig

Description of Business and Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Description of Business and Significant Accounting Policies	Description of Business and Significant Accounting Policies 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 that are designed to enhance and transform CSP access networks to meet the changing demands of subscribers rapidly and cost-effectively. Basis of Presentation 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. The accompanying 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”). In the opinion of management, the consolidated 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. Applicable Accounting Guidance Any reference in these notes to applicable accounting guidance (“guidance”) is meant to refer to the authoritative U.S. generally accepted accounting principles ("GAAP") as found in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”). Use of Estimates The preparation of financial statements is in conformity with U.S. GAAP, which requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. For the Company, these estimates include, but are not limited to: allowances for doubtful accounts and sales returns, excess and obsolete inventory, allowances for obligations to its contract manufacturers, valuation of stock-based compensation, useful lives assigned to long-lived assets and acquired intangible assets, standard and extended warranty costs, and contingencies. Actual results could differ from those estimates, and such differences could be material to the Company's financial position and results of operations. Revenue Recognition The Company derives revenue primarily from the sale of hardware products and related software. Revenue is recognized when all of the following criteria have been met: • Persuasive evidence of an arrangement exists. The Company generally relies upon sales agreements and customer purchase orders as evidence of an arrangement. • Delivery has occurred. The Company uses the shipping terms of the arrangement or evidence of customer acceptance to verify delivery or performance. • Sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on the payment terms and whether the sales price is subject to refund or adjustment. Payment terms to customers can range from net 30 to net 120 days. • Collectability is reasonably assured. The Company assesses collectability based primarily on creditworthiness of customers and their payment histories. Revenue from installation and training services are recognized as the services are completed. Post-sales software support revenue and extended warranty services revenue are deferred and recognized ratably over the period during which the services are to be performed. In instances where substantive acceptance provisions are specified in the customer agreement, revenue is deferred until all acceptance criteria have been met. From time to time, the Company offers customers sales incentives, which include volume rebates and discounts. These amounts are estimated on a quarterly basis and recorded as a reduction of revenue. The Company enters into arrangements with certain of its customers who receive government supported loans and grants from the U.S. Department of Agriculture's Rural Utility Service (“RUS”) to finance capital spending. Under the terms of an RUS equipment contract that includes installation services, the customer does not take possession and control and title does not pass until formal acceptance is obtained from the customer. Under this type of arrangement, the Company does not recognize revenue until it has received formal acceptance from the customer. For RUS arrangements that do not involve installation services, the Company recognizes revenue in accordance with the revenue recognition policy described above. The Company's products contain both software and non-software components that function together to deliver the products' essential functionality. When the Company enters into sales arrangements that consist of multiple deliverables of its product and service offerings, the Company allocates the total consideration of the arrangement to each separable deliverable based on its relative selling price. The Company limits the amount allocable to delivered elements to the amount that is not contingent upon the delivery of additional items or meeting specified performance conditions, and recognizes revenue on each deliverable in accordance with its revenue recognition policy. The determination of selling price for each deliverable is based on a selling price hierarchy, which is vendor-specific objective evidence (“VSOE”) if available, third-party evidence (“TPE”) if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor TPE is available. VSOE of selling price is based on the price charged when the element is sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices of an element fall within a narrow range when each element is sold separately. The Company has established VSOE for its training and post-sales software support services based on the normal pricing practices of these services when sold separately. TPE of selling price is established by evaluating whether there are similar competitor products or services that are sold in stand-alone sales transaction to similarly situated customers. Generally, the Company's marketing strategy differs from that of its peers and its offerings contain a significant level of customization and differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Additionally, as the Company is unable to reliably determine what similar competitor products' selling prices are on a stand-alone basis, it is not typically able to determine TPE. ESP is established considering multiple factors including, but not limited to geographies market conditions, competitive landscape, internal costs, gross margin objectives, characteristics of targeted customers and pricing practices. The determination of ESP is made through consultation with and formal approval by management, taking into consideration the go-to-market strategy. Cost of Revenue Cost of revenue consists primarily of finished goods inventory purchased from the Company’s contract manufacturers, payroll and related expenses associated with managing the relationships with contract manufacturers, depreciation of manufacturing test equipment, warranty costs, excess and obsolete inventory costs, shipping charges, and amortization of certain intangible assets. Warranty The Company offers limited warranties for its hardware products for a period of one , three or five years, depending on the product type. Warranty service revenues are deferred and recognized ratably over the period during which the services are to be performed. The Company recognizes estimated costs related to warranty activities as a component of cost of revenue upon product shipment or upon identification of a specific product failure. The estimates are based upon historical and projected product failure and claim rates, historical costs incurred in correcting product failures and information available related to any specifically identified product failures. The recorded amount is adjusted from time to time for specifically identified warranty exposure. Actual warranty expenses are charged against the Company’s estimated warranty liability when incurred. Factors that affect the Company’s warranty liability include the number of installed units and historical and anticipated rates of warranty claims and cost per claim. Stock-Based Compensation In accordance with ASC Topic 718, “ Compensation - Stock Compensation ” (“ASC Topic 718”), stock-based awards are recorded at fair value as of the grant date and recognized to expense over the employee’s requisite service period (generally the vesting period), which the Company has elected to amortize on a straight-line basis. Stock-based compensation expense is reduced by the Company’s estimated forfeitures on all unvested awards. The fair value of stock option and employee stock purchase right is estimated at the grant date using the Black-Scholes option valuation model. The fair value of restricted stock unit and restricted stock award is based on the closing market price of the Company's common stock on the date of grant. The fair value of performance restricted stock unit (“PRSU”) with a market condition is estimated on the date of grant, using a Monte Carlo simulation model to estimate the total return ranking 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. Research and Development Research and development costs include costs of developing new products and processes, as well as design and engineering costs. Such costs are charged to research and development expense as incurred. Development costs related to software incorporated in the Company’s products incurred subsequent to the establishment of technological feasibility are capitalized and amortized over the estimated useful lives of the related products. Technological feasibility is established upon completion of a working model. Software development costs required to be capitalized under ASC 985-20, Costs of Software to be Sold, Leased or Marketed, and under ASC 350-40, Internal-Use Software, were not material to our consolidated financial statements in fiscal 2015 , 2014 and 2013 . Loss Contingencies From time to time, the Company is involved in legal proceedings arising from the normal course of business activities. The Company evaluates the likelihood of an unfavorable outcome of legal proceedings to which it is a party and accrues a loss contingency when the loss is probable and reasonably estimable. Assessing legal contingencies involves significant judgment and estimates and the outcome of litigation is inherently uncertain and subject to numerous factors outside the Company's control. Significant judgment is required when the Company assesses the likelihood of any adverse judgments or outcomes, including the potential range of possible losses, and whether losses are probable and reasonably estimable. The Company offers limited warranties for its hardware products for a period of one , three or five years, depending on the product type. The Company estimates costs related to warranty activities based upon historical and projected product failure and claim rates, historical costs incurred in correcting product failures and information available related to any specifically identified product failures. The Company recognizes estimated warranty costs when it is probable that a liability has been incurred and the amount of loss is reasonably estimable. Significant judgment is required in estimating costs associated with warranty activities and the Company estimates are limited to information available to the Company at the time of such estimates. In some cases, such as when a specific product failure is first identified or a new product is introduced, the Company may initially have limited information and limited historical failure and claim rates upon which to base its estimates, and such estimates may require revision in future periods. Because of uncertainties related to these matters, the Company bases its estimates of whether a loss contingency is probable or reasonably possible, as well as the reasonable range of possible losses associated with each loss contingency, only on the information available at the time. As additional information becomes available, and at least quarterly, the Company reassesses the potential liability on each significant matter and may revise its estimates. These revisions could have a material impact on the Company's business, operating results or financial condition. The actual outcome of these legal proceedings may materially differ from the Company's estimates of potential liability, which could have a material adverse effect on the Company's business, operating results or financial condition. 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. Credit Risk and Inventory Supplier Concentrations Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. Cash equivalents consist of money market funds, which are invested through financial institutions in the United States. Deposits in these financial institutions may, at times, exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company also has approximately $5.4 million of cash held by its foreign subsidiaries in Brazil, China and the United Kingdom. Management believes that the financial institutions that hold the Company’s cash and cash equivalents are financially sound and, accordingly, minimal credit risk exists with respect to these cash and cash equivalents. Concentrations of credit risk in relation to customer with an accounts receivable balance of 10% or greater of total accounts receivable and customer with net revenues of 10% or greater of total revenues are presented below for the periods indicated. Percentage of Accounts Receivable Percentage of Revenue At December 31, Years Ended December 31, 2015 2014 2015 2014 2013 CenturyLink 27% * 22% 23% 26% * Less than 10% of total accounts receivable. The Company maintains an allowance for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. The Company records a specific allowance based on an analysis of individual past-due balances. Additionally, based on its historical write-offs and collections experience, the Company records an additional allowance based on a percentage of outstanding receivables. The Company performs credit evaluations of its customers’ financial condition. These evaluations require significant judgment and are based on a variety of factors including, but not limited to, current economic trends, payment history and financial review of the customer. Actual collection losses may differ from management’s estimates, and such differences could be material to the Company’s financial position and results of operations. The Company depends primarily on a small number of outside contract manufacturers for the bulk of its finished goods inventory. In particular, the Company relies on Flextronics for the manufacture of a large percentage of its products. The Company generally purchases its products through purchase orders with its suppliers or contract manufacturers. While the Company seeks to maintain a sufficient reserve of its products, the Company’s business and results of operations could be adversely affected by a stoppage or delay in receiving such products, the receipt of defective parts, an increase in price of such products or the Company’s inability to obtain lower prices from its contract manufacturers and suppliers in response to competitive pressures. Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, marketable securities, trade receivables, accounts payable, and other accrued liabilities approximate their fair value due to their relatively short-term nature. 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 and marketable securities are stated at amounts that approximate fair value based on quoted market prices. 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 comprehensive 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 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 December 31, 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. Restricted Cash As of December 31, 2014, the Company had $0.3 million cash restricted for collateralizing the outstanding letters of credit with Silicon Valley Bank, which restriction was subsequently released during the first quarter of 2015. Allowance for Doubtful Accounts The Company maintains an allowance for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. The Company records a specific allowance based on an analysis of individual past-due balances. Additionally, based on historical write-offs and the Company's collection experience, the Company records an additional allowance based on a percentage of outstanding receivables. The Company performs credit evaluations of its customers’ financial condition. These evaluations require significant judgment and are based on a variety of factors including, but not limited to, current economic trends, payment history and a financial review of the customer. Actual collection losses may differ from management’s estimates, and such differences could be material to our financial position and results of operations. Inventory Valuation Inventory, which primarily consists of finished goods purchased from contract manufacturers, is stated at the lower of cost, determined by the first-in, first-out method, or market value. Inbound shipping costs are included in cost of inventory. In addition, the Company, from time to time, procures component inventory primarily as a result of manufacturing discontinuation of critical components by suppliers. The Company regularly monitors inventory quantities on hand and records write-downs for excess and obsolete inventories based on the Company’s estimate of demand for its products, potential obsolescence of technology, product life cycles, and whether pricing trends or forecasts indicate that the carrying value of inventory exceeds its estimated selling price. These factors are impacted by market and economic conditions, technology changes, and new product introductions and require estimates that may include elements that are uncertain. Actual demand may differ from forecasted demand and may have a material effect on gross margins. If inventory is written down, a new cost basis is established that cannot be increased in future periods. Shipments from our suppliers or contract manufacturers before the Company receives them are recorded as in-transit inventory when title and the significant risks and rewards of ownership have passed to the Company. Deferred Revenue and Deferred Cost of Revenue Deferred revenue results from transactions where the Company billed the customer for product shipped or services performed but not all revenue recognition criteria have been met. When the Company’s products have been shipped, but the product revenue associated with the arrangement has been deferred as a result of not meeting the criteria for immediate revenue recognition, the Company also defers the related inventory costs for the delivered items until all criteria are met for revenue recognition. The Company defers tangible direct costs associated with hardware products delivered based on the inventory cost at the time of shipment. Certain costs directly related to the delivery of professional services that cannot be accounted for separately from the undelivered items included in a multiple element arrangement are also capitalized and deferred, if deemed recoverable, until all revenue recognition criteria are met. Accordingly, all cost of services incurred directly related to the delivery of an inseparable professional service item in which revenue has not yet been recognized are deferred and recorded within "Deferred cost of revenue" in the Company's Consolidated Balance Sheets. We evaluate deferred cost of revenue for recoverability based on multiple factors, including whether net revenues will exceed the amount of deferred cost of revenue based on the terms of the overall arrangement. To the extent that deferred cost of revenue is determined to be unrecoverable, we adjust deferred cost of revenue with a charge to cost of revenue in the current period. In connection with our recoverability assessments, we have not incurred significant impairment charges through December 31, 2015 . We recognize deferred revenue and associated deferred cost of revenue, as revenue and cost of revenue respectively, in the Consolidated Statements of Comprehensive Loss once all revenue recognition criteria have been met. Property and Equipment Property and equipment are stated at cost, less accumulated depreciation, and are depreciated using the straight-line method over the estimated useful life of each asset. Computer equipment is depreciated over two years; purchased software is depreciated over three years; test equipment is depreciated over three years; furniture and fixtures are depreciated over seven years; and leasehold improvements are depreciated over the shorter of the respective lease term or the estimated useful life of the asset. Maintenance and repairs are charged to expense as incurred. Goodwill The Company records goodwill when consideration paid in a business acquisition exceeds the fair value of the net tangible assets and the identified intangible assets acquired. Goodwill is not amortized but instead is subject to an annual impairment test or more frequently if events or changes in circumstances indicate that it may be impaired. The Company evaluates goodwill on an annual basis as of the end of the second quarter of each fiscal year. Management has determined that it operates as a single reporting unit and, therefore, evaluates goodwill impairment at the enterprise level. In an annual impairment test, the Company first assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. In assessing the qualitative factors, management considers 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. If the Company determines as a result of the qualitative assessment that it is more likely than not (that is, a likelihood of more than 50 percent) that the fair value of a reporting unit is less than its carrying amount, then the quantitative test is required. Otherwise, no further testing is required. In a quantitative test, the Company compares its fair value to its carrying value including goodwill. The Company determines its fair value using both an income approach and a market approach. Under the income approach, the Company determines fair value based on estimated future cash flows, discounted by an estimated weighted-average cost of capital, which reflects the overall level of inherent risk of the Company and the rate of return an outside investor would expect to earn. Under the market-based approach, the Company utilizes information regarding the Company as well as publicly available industry information to determine earnings multiples that are used to value the Company. If the carrying value of the Company exceeds its fair value, the Company will determine the amount of impairment loss by comparing the implied fair value of goodwill with the carrying value of goodwill. An impairment charge is recognized for the excess of the carrying value of goodwill over its implied fair value. At the end of the second quarter of 2015 , the Company has completed its annual goodwill impairment test. Based on its assessment of the above qualitative factors, 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 quantitative goodwill impairment test at the time. There have been no significant events or changes in circumstances subsequent to the 2015 annual impairment test that would more likely than not indicate that the carrying value of goodwill may have been impaired as of December 31, 2015 . Therefore, there was no impairment to the carrying value of the Company's goodwill as of December 31, 2015 . As described above, the Company’s estimate of its fair value depends upon a number of qualitative and quantitative factors. Although the Company has concluded that there was no impairment to the carrying value of goodwill as of December 31, 2015 , the Company’s stock price and market capitalization have declined since December 31, 2015 . The estimated fair value of the Company exceeded carrying value by approximately $154.7 million or 59% , and $153.8 million or 65% , using the market capitalization on the annual impairment testing date and December 31, 2015 , respectively. If the Company will experience a sustained decline in its stock price and market capitalization, or if the Company’s stock price will decline below its book value, the estimated fair value of the Company would be negatively impacted, and the Company would be required to reassess possible impairment of the carrying value of our goodwill. There were no impairment losses for goodwill during 2014 and 2013 . Intangible Assets and Other Long-Lived Assets Intangible assets with finite useful lives are amortized over their estimated useful life. The Company periodically evaluates long-lived assets, including intangible assets, for impairment whenever events or changes in circumstances indicate that a potential impairment may have occurred. If such events or changes in circumstances arise, the Company compares the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the assets. The Company has reviewed events and changes to its business during the year and has determined that there was no impairment to its intangible assets and other long-lived assets during 2015 . The Company did not incur any impairment losses for intangible assets and other long-lived assets during 2014 and 2013 . Income Taxes The Company evaluates its tax positions and estimates its current tax exposure along with assessing temporary differences that result from different book to tax treatment of items not currently deductible for tax purposes. These differences result in deferred tax assets and liabilities on the Company’s balance sheets, which are estimated based upon the difference between the financial statement and tax bases of assets and liabilities using the enacted tax rates that will be in effect when these differences reverse. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the Company’s statements of operations become deductible expenses under applicable income tax laws or loss or credit carryforwards are utilized. Accordingly, realization of the Company’s deferred tax assets is dependent on future taxable income against which these deductions, losses and credits can be utilized. The Company must assess the likelihood that the Company’s deferred tax assets will be recovered from future taxable income, and to the extent the Company believes that recovery is not more likely than not, the Company must establish a valuation allowance. Management judgment is required in determining the Company’s provision for income taxes, the Company’s deferred tax assets and liabilities and any valuation allowance recorded against the Company’s net deferred tax assets. Excluding our foreign operations, the Company recorded a full valuation allowance at each balance sheet date presented because, based on the available evidence, the Company believes it is more likely than not that it will not be able to utilize all of its deferred tax assets in the future. The Company intends to maintain the full valuation allowances until sufficient evidence exists to support the reversal of the valuation allowances. Foreign Currency Translation Assets and liabilities of the Company’s wholly owned foreign subsidiaries are translated from their respective functional currencies at exchange rates in effect at the balance sheet date, and revenues and expenses are translated at the monthly average exchanges rates. Translation adjustments are reflected as a separate compo

Cash, Cash Equivalents and Mark

Cash, Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash, Cash Equivalents, and Marketable Securities	Cash, Cash Equivalents and Marketable Securities Cash, cash equivalents and marketable securities consisted of the following (in thousands): December 31, December 31, Cash and cash equivalents: Cash $ 13,378 $ 17,866 Money market funds 10,248 30,963 Total cash and cash equivalents 23,626 48,829 Marketable securities: Corporate debt securities 35,799 61,050 U.S. government agency securities 10,520 — Commercial paper 3,645 1,800 Total marketable securities 49,964 62,850 Total cash, cash equivalents and marketable securities $ 73,590 $ 111,679 The carrying amounts of our money market funds approximate their fair values due to their nature, duration and short maturities. The amortized cost and fair value of marketable securities as of December 31, 2015 were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 35,869 $ 2 $ (72 ) $ 35,799 U.S. government agency securities 10,544 — (24 ) 10,520 Commercial paper 3,645 — — 3,645 Total marketable securities $ 50,058 $ 2 $ (96 ) $ 49,964 The amortized cost and fair value of marketable securities as of December 31, 2014 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 December 31, 2015 and December 31, 2014 , there are no marketable securities, classified and accounted for as available-for-sale securities that have been in a continuous unrealized loss position in excess of twelve months. As of December 31, 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 $ 38,714 $ 38,651 Due in 1-2 years 11,344 11,313 Total marketable securities $ 50,058 $ 49,964

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements In accordance with 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 fair value hierarchy also requires the Company to maximize the use of observable inputs, when available, and to minimize the use of unobservable inputs when determining inputs and determining fair value. The following table sets forth the Company's financial assets measured at fair value as of December 31, 2015 and 2014 , based on the three-tier fair value hierarchy (in thousands): As of December 31, 2015 Level 1 Level 2 Total Money market funds $ 10,248 $ — $ 10,248 Corporate debt securities — 35,799 35,799 U.S. government agency securities — 10,520 10,520 Commercial paper — 3,645 3,645 Total $ 10,248 $ 49,964 $ 60,212 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 twelve months ended December 31, 2015 and 2014 .

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 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 or impairment to goodwill since the acquisition dates. Intangible Assets Intangible assets are carried at cost, less accumulated amortization. The details of intangible assets as of December 31, 2015 and 2014 are disclosed in the following table (in thousands): December 31, 2015 December 31, 2014 Gross Accumulated Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (64,047 ) $ 4,917 $ 68,964 $ (55,694 ) $ 13,270 Customer relationships 54,740 (53,039 ) 1,701 54,740 (42,831 ) 11,909 Total intangible assets, excluding goodwill $ 123,704 $ (117,086 ) $ 6,618 $ 123,704 $ (98,525 ) $ 25,179 Amortization expense for intangible assets was $18.6 million , $18.6 million , and $18.6 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. Expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense 2016 5,805 2017 813 Total $ 6,618

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Balance Sheet Details	Balance Sheet Details Accounts receivable, net consisted of the following (in thousands): December 31, December 31, Accounts receivable $ 48,319 $ 31,493 Allowance for doubtful accounts (501 ) (241 ) Product return reserve (663 ) (508 ) Accounts receivable, net $ 47,155 $ 30,744 The table below summarizes the changes in allowance for doubtful accounts and product return reserve for the periods indicated (in thousands): Additions Charged to Balance Costs or Deductions at Beginning of Expenses or and Write Balance at Year Revenue Offs End of Year Year Ended December 31, 2015 Allowance for doubtful accounts $ 241 $ 405 $ (145 ) $ 501 Product return reserve 508 4,224 (4,069 ) 663 Year Ended December 31, 2014 Allowance for doubtful accounts $ 358 $ 154 $ (271 ) $ 241 Product return reserve 764 4,805 (5,061 ) 508 Year Ended December 31, 2013 Allowance for doubtful accounts $ 421 $ (13 ) $ (50 ) $ 358 Product return reserve 1,740 3,535 (4,511 ) 764 Inventory consisted of the following (in thousands): December 31, December 31, Raw materials $ 2,209 $ 3,180 Finished goods 45,458 43,573 Total inventory $ 47,667 $ 46,753 Property and equipment, net consisted of the following (in thousands): December 31, December 31, Test equipment $ 39,035 $ 40,766 Computer equipment and purchased software 27,736 30,355 Furniture and fixtures 1,833 1,852 Leasehold improvements 6,554 6,550 Total 75,158 79,523 Accumulated depreciation and amortization (58,009 ) (59,379 ) Property and equipment, net $ 17,149 $ 20,144 Depreciation and amortization expense was $10.3 million , $9.3 million , $10.2 million for the years ended December 31, 2015 , 2014 , and 2013 , respectively. Accrued liabilities consisted of the following (in thousands): December 31, December 31, Accrued compensation and related benefits $ 13,809 $ 15,782 Accrued warranty 9,564 9,553 Accrued professional and consulting fees 2,813 5,860 Advance customer payments 1,094 364 Accrued excess and obsolete inventory at contract manufacturers 1,011 888 Accrued non income related taxes 905 581 Accrued customer rebates 784 851 Accrued business travel expenses 580 1,414 Accrued freight 486 303 Accrued hosting services 466 235 Accrued rent 381 412 Income taxes payable 322 269 Accrued other 3,297 2,931 Total accrued liabilities $ 35,512 $ 39,443 Deferred revenue consisted of the following (in thousands): December 31, 2015 December 31, 2014 Current: Product and services $ 8,937 $ 9,753 Extended warranty 3,187 2,969 12,124 12,722 Non-current: Product and services 58 182 Extended warranty 19,511 19,211 19,569 19,393 Total deferred revenue $ 31,693 $ 32,115 Deferred cost of revenue consisted of costs incurred for products and services for which revenues have been deferred.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Lease Commitments The Company leases office space under non-cancelable operating leases. Certain of the Company’s operating leases contain renewal options and rent acceleration clauses. Future minimum payments under the non-cancelable operating leases consisted of the following as of December 31, 2015 (in thousands): Period Minimum Future Lease Payments 2016 $ 2,666 2017 2,594 2018 2,325 2019 579 2020 222 Thereafter 248 Total $ 8,634 The Company leases its primary office space in Petaluma, California under a lease agreement ("Petaluma Lease") that extended through February 2014. On January 28, 2013, the Company entered into an amendment to its Petaluma Lease ("Amendment") to extend the lease term to February 2019. In connection with the Petaluma Lease and the Amendment, the Company received lease incentives of $1.2 million and $0.4 million , respectively, which can be used for leasehold improvements or be applied as credits to rent payments. The Company had capitalized the full amount of the lease incentives upon inception of the respective agreement and these incentives are being amortized to reduce rent expense over the extended lease term. As of December 31, 2015 , total unamortized lease incentive was $0.3 million of which $0.1 million and $0.2 million were included in "Accrued liabilities" and "Other long-term liabilities", respectively, in the Consolidated Balance Sheet as of December 31, 2015 . Payments under the Company’s operating leases that escalate over the term of the lease are recognized as rent expense on a straight-line basis. The above table also includes future minimum lease payments primarily for our facilities in Minneapolis, Minnesota; Acton, Massachusetts; Nanjing, China; Richardson, Texas; and San Jose, and Santa Barbara, California, which expire at various dates through 2022. For the years ended December 31, 2015 , 2014 and 2013 , total rent expense of the Company, net of sublease income, was $3.5 million , $4.1 million , $3.9 million , respectively. Purchase Commitments The Company’s primary contract manufacturers place orders for component inventory in advance based upon the Company’s build forecasts in order to reduce manufacturing lead times and ensure adequate component supply. The components are used by the contract manufacturers to build the products included in the build forecasts. The Company does not take ownership of the components and any outstanding orders do not represent firm purchase commitments pursuant to the Company’s agreement with the contract manufacturer. The Company will provide purchase orders to its contract manufacturers in order to fulfill its monthly finished product inventory requirements. The Company incurs a liability when the contract manufacturer has converted the component inventory to a finished product and takes ownership of the inventory when transferred to the designated shipping warehouse. However, historically, the Company has reimbursed its primary contract manufacturer for component inventory purchases when this inventory has been rendered excess or obsolete, for example due to manufacturing and engineering change orders resulting from design changes, manufacturing discontinuation of parts by its suppliers, or in cases where inventory levels greatly exceed projected demand. The estimated excess and obsolete inventory liabilities related to such manufacturing and engineering change orders and other factors, which are included in accrued liabilities in the accompanying balance sheets, were $1.0 million and $0.9 million as of December 31, 2015 and 2014 , respectively. The Company records these amounts in cost of products and services in its Consolidated Statements of Comprehensive Loss. As of December 31, 2015 , the Company had non-cancelable outstanding purchase orders of $7.3 million for inventories to be delivered by its suppliers, including contract manufacturers, within one year. Contingencies The Company evaluates the circumstances regarding outstanding and potential litigation and other contingencies on a quarterly basis to determine whether there is at least a reasonable possibility that a loss exists requiring accrual or disclosure, and if so, whether an estimate of the possible loss or range of loss can be made, or whether such an estimate cannot be made. When a loss is probable and reasonably estimable, the Company accrues for such amount based on its estimate of the probable loss considering information available at the time. When a loss is reasonably possible, the Company discloses the estimated possible loss or range of loss in excess of amounts accrued if material. Except as otherwise disclosed below, the Company does not believe that there was a reasonable possibility that a material loss may have been incurred with respect to the matters disclosed. Accrued Warranty The Company provides a warranty for its hardware products. Hardware generally has a one , three or five -year warranty from the date of shipment. The Company accrues for potential warranty claims based on the Company’s historical product failure rates and historical costs incurred in correcting product failures. The Company's warranty accruals are based on estimates of losses that are probable based on information available. The adequacy of the accrual is reviewed on a periodic basis and adjusted, if necessary, based on additional information as it becomes available. Changes in the Company’s warranty reserve in the periods as indicated were as follows (in thousands): Years Ended December 31, 2015 2014 2013 Balance at beginning of period $ 9,553 $ 10,856 $ 11,762 Warranty charged to cost of revenue 4,661 3,394 4,350 Utilization of warranty (4,115 ) (3,328 ) (4,786 ) Adjustments to pre-existing warranty (535 ) (1,369 ) (470 ) Balance at end of period $ 9,564 $ 9,553 $ 10,856 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 initially closed on April 30, 2013. On June 11, 2013, the plaintiffs filed their Second Amended Class Action Complaint for Breach of Fiduciary Duty (“Second Amended Complaint”). The Second Amended Complaint adds Occam's former CFO as a defendant, and alleges that each of the defendants breached their fiduciary duties by failing to attempt to obtain the best purchase price for Occam and failing to disclose certain allegedly material facts about the merger transaction in the preliminary proxy statement and prospectus included in the Registration Statement on Form S-4 filed with the SEC on November 2, 2010. On July 17, 2013, attorneys representing all of the defendants named in the Second Amended Complaint filed Defendants' Opening Brief in Support of Their Motion for Summary Judgment, arguing that all defendants are entitled to summary judgment on all counts of the Second Amended Complaint. Plaintiffs' answering brief to the motion for summary judgment was filed on September 3, 2013, and defendants' reply brief was filed on October 4, 2013. A hearing on the motion for summary judgment was held on December 6, 2013. On April 8, 2014, the 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 scheduled with the court 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 expects that a considerable portion of its remaining defense costs, including costs of the trial, along with any liability imposed upon the Company following trial, will exceed its remaining available Directors & Officers liability insurance coverage. As described above, the legal proceedings have been protracted as plaintiffs continue to seek additional discovery following the court’s order re-opening discovery and, most recently, with the addition of Wilson Sonsini as a defendant in the action. The Company has also continued to incur certain expenses that are not covered by insurance. Following Jefferies' demand for indemnification the Company notified Occam’s insurance carriers, and such carriers 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 are not 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. Guarantees The Company from time to time enters into contracts that require it to indemnify various parties against claims from third parties. These contracts primarily relate to (i) certain real estate leases, under which the Company may be required to indemnify property owners for environmental and other liabilities, and other claims arising from the Company’s use of the applicable premises, (ii) certain agreements with the Company’s officers, directors, and employees, under which the Company may be required to indemnify such persons for liabilities arising out of their relationship with the Company, (iii) contracts under which the Company may be required to indemnify customers against third-party claims that a Company product infringes a patent, copyright, or other intellectual property right and (iv) procurement or license agreements, under which the Company may be required to indemnify licensors or vendors for certain claims that may be brought against them arising from the Company’s acts or omissions with respect to the supplied products or technology. Generally, a maximum obligation under these contracts is not explicitly stated. Because the obligated amounts associated with these types of agreements are not explicitly stated, the overall maximum amount of the obligation cannot be reasonably estimated. Historically, the Company has not been required to make payments under these obligations, and no liabilities have been recorded for these obligations in the Company’s balance sheets.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share The following table sets forth the computation of basic and diluted net loss per share for the periods indicated (in thousands, except per share data): Years Ended December 31, 2015 2014 2013 Numerator: Net loss $ (26,333 ) $ (20,814 ) $ (17,265 ) Denominator: Weighted-average common shares outstanding 51,489 50,808 49,419 Basic and diluted net loss per common share $ (0.51 ) $ (0.41 ) $ (0.35 ) Potentially dilutive shares, weighted-average 6,120 5,020 5,308 For all the three years presented, unvested restricted stock awards are included in the calculation of basic weighted-average shares because such shares are participating securities, however the impact was immaterial. Potentially dilutive shares are excluded from the computation of diluted net loss per common share because their effect is antidilutive. These antidilutive shares were primarily from stock options, restricted stock units and performance restricted stock awards. We have incurred a net loss for all periods presented, hence, 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.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Stockholders' Equity	Stockholders’ Equity Common Stock On March 2, 2010, the Company’s board of directors approved an amended and restated certificate of incorporation that increased the authorized common stock to 100 million shares and the authorized preferred stock to 5.0 million shares effective immediately prior to the completion of the Company’s initial public offering on March 26, 2010 . On March 21, 2010, the Company’s board of directors approved an amended and restated certificate of incorporation effecting a 2-for-3 reverse stock split of its common stock and all convertible preferred stock. The par value and the authorized shares of the common stock and convertible preferred stock were not adjusted as a result of the reverse stock split. All issued and outstanding common stock, convertible preferred stock, warrants for common stock, warrants for preferred stock, and per share amounts contained in the financial statements have been retroactively adjusted to reflect this reverse stock split for all periods presented. The reverse stock split was effected on March 23, 2010. On March 26, 2010 , the Company completed its initial public offering in which 4,166,666 shares of common stock were sold by the Company at a public offering price of $13.00 per share. Gross proceeds of $54.2 million from the sale of common stock by the Company were reduced by issuance costs of $4.6 million and underwriters fees of $3.8 million . On April 8, 2010 , the Company issued and sold 949,339 shares of common stock resulting from the exercise of the underwriters’ option to purchase common shares associated with the Company’s initial public offering. This sale resulted in gross proceeds of $12.3 million based on an initial public offering price of $13.00 per share of common stock, which were reduced by underwriters’ discount and offering expenses payable by the Company of $0.8 million . On February 22, 2011, in connection with the acquisition of Occam, the Company issued 6.4 million shares of the Company’s common stock, a value of $117.2 million . Holders of our common stock are entitled to receive dividends, if any, as may be declared from time to time by our board of directors out of legally available funds. No dividends have been declared or paid as of December 31, 2015 . In the event of our liquidation, dissolution or winding up, holders of our common stock will be entitled to share ratably in the net assets legally available for distribution to stockholders after the payment of all of our debts and other liabilities and the satisfaction of any liquidation preference granted to the holders of any then outstanding shares of preferred stock. Preferred Stock The board of directors has the authority, without action by stockholders with the exception of stockholders who hold board positions, to designate and issue up to 5.0 million shares of preferred stock in one or more series and to fix the rights, preferences, privileges and restrictions thereof. These rights, preferences and privileges could include dividend rights, conversion rights, voting rights, terms of redemption, liquidation preferences, sinking fund terms and the number of shares constituting any series or the designation of such series, any or all of which may be greater than the rights of common stock. The issuance of the Company’s preferred stock could adversely affect the voting power of holders of common stock and the likelihood that such holders will receive dividend payments and payments upon liquidation. In addition, the issuance of preferred stock could have the effect of delaying, deferring or preventing a change in control of the Company or other corporate action. Subsequent to the Company’s initial public offering and the conversion of all preferred stock outstanding at that date, the board of directors has not designated any rights, preference or powers of any preferred stock and no shares of preferred stock have been issued. Equity Incentive Plans Prior to March 2010, the Company had the Amended and Restated 2002 Stock Plan ("2002 Plan"). Under the 2002 Plan, the Company may grant incentive stock options at a price not less than 100% of the fair market value of the common stock on the date of grant and non-statutory stock options at a price not less than 100% of the fair market value of the common stock on the date of grant. Before April 2004, certain options could be granted with the right to exercise those options before vesting. The majority of the stock options granted under the 2002 Plan vest over 4 years and expire in 10 years . On March 2, 2010, the Company’s Board of Directors approved the 2010 Equity Incentive Award Plan ("2010 Plan") which allows the Company to grant stock options, restricted stock awards ("RSA"), restricted stock units ("RSU"), performance restricted stock units ("PRSU"), stock appreciation rights, dividend equivalents, deferred stock, and stock payments to employees, directors and consultants of the Company. A total of 4,666,666 shares of common stock were reserved for future issuance under the 2010 Plan, which became effective upon the completion of the Company’s initial public offering of common stock. In addition, on the first day of each year beginning in 2011 and ending in 2020, the 2010 Plan provides for an annual automatic increase to the shares reserved for issuance and no more than 17,150,494 shares of Common Stock may be issued upon the exercise of Incentive Stock Options. Pursuant to the automatic annual increase, a total of 3,333,330 additional shares had been reserved under the 2010 Plan since 2011. Upon the effectiveness of the 2010 Plan, equity awards were granted only under the 2010 Plan and shares of common stock previously reserved for issuance under the Prior Plans became available for issuance under the 2010 Plan. To date, awards granted under the 2010 Plan consist of stock options, RSAs, RSUs and PRSUs. Stock options granted under the 2010 Plan are granted in general at a price not less than 100% of the fair market value of the common stock on the date of grant. Generally, the options issued under the 2010 Plan vest 25% on the first anniversary of the vesting commencement date and on a monthly basis thereafter for a period of an additional three years . The options have a maximum term of ten years . Each RSU granted under the 2010 Plan represents a right to receive one share of the Company’s common stock (subject to adjustment for certain specified changes in the capital structure of the Company) upon the completion of a specific period of continued service. The majority of RSUs granted vest over four years . In July 2011, the Company granted 423,000 RSAs to executives under the 2010 Plan, which vest 25% per year for 4 years from the grant date . Upon issuance of RSA, the holder is entitled to have all the rights of a stockholder, subject to the restrictions in his or her Award Agreement, including the right to receive all dividends and other distributions paid or made with respect to the shares. 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. 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. Stock Options The following table summarizes the activity of stock options under the Company’s equity incentive plans (in thousands, except per share data): Weighted- Weighted-Average Average Remaining Aggregate Number of Exercise Price Contractual Life Intrinsic Stock Options Shares Per Share (in years) Value (1) Outstanding as of December 31, 2014 3,701 $ 11.38 Granted 200 8.91 Exercised (97 ) 6.56 Forfeited (1,043 ) 10.07 Expired (106 ) 13.29 Outstanding as of December 31, 2015 2,655 $ 11.81 6.7 $ 250 Vested and expected to vest as of December 31, 2015 2,594 $ 11.89 6.6 $ 250 Options exercisable as of December 31, 2015 1,822 $ 13.32 5.9 $ 240 (1) Amounts represent the difference between the exercise price and the fair market value of common stock at December 31, 2015 for all in the money options outstanding. During the years ended December 31, 2015 , 2014 , and 2013 , total intrinsic value of stock options exercised was $0.3 million , $0.6 million , $1.0 million , respectively. Total cash received from employees as a result of stock option exercises in 2015 , 2014 and 2013 was $0.6 million , $1.7 million , $0.7 million , respectively. Total fair values of stock options vested during 2015 , 2014 and 2013 was $2.8 million , $3.7 million , $3.9 million , respectively. Restricted Stock Units, Performance Restricted Stock Units, and Restricted Stock Awards The following table summarizes the activities of the Company's RSUs, PRSUs, and RSAs under the Company’s equity incentive plans (in thousands, except per share data): RSUs PRSUs RSAs Weighted-Average Weighted-Average Weighted-Average Grant Date Grant Date Grant Date Number of Fair Value Number of Fair Value Number of Fair Value Shares Per Share Shares Per Share Shares Per Share Outstanding at December 31, 2014 1,734 $ 9.53 362 $ 10.53 62 $ 21.67 Granted 1,608 8.59 — — — — Vested (706 ) 10.56 (148 ) 11.60 (62 ) 21.67 Canceled (167 ) 9.23 (30 ) 13.33 — — Outstanding at December 31, 2015 2,469 $ 8.64 184 $ 9.21 — $ — Upon vesting of certain RSUs, PRSUs and RSAs, the Company withheld shares with value equivalent to the employees’ minimum statutory obligation for the applicable income and other employment taxes, and remitted the cash to the appropriate taxing authorities. The number of shares withheld was based on the value of the RSUs, PRSUs or RSAs on their vesting date as determined by the Company’s closing stock price. The withheld shares are reserved for future grant and issuance under the 2010 Plan. 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 would terminate 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 is $0.6 million , which is being recognized on a straight-line basis over the remaining service period through the Termination Date. During the years ended December 31, 2014 and 2013, $0.1 million and $0.5 million , respectively, of the total fair value has been recognized in general and administrative expenses of the Consolidated Statement of Comprehensive Loss in this Form 10-K. There was no expense recognized during fiscal 2015 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. Employee Stock Purchase Plan The Company’s 2010 Employee Stock Purchase Plan, as amended (“2010 ESPP”) allows employees to purchase shares of the Company’s common stock through payroll deductions of up to 15 percent of their annual compensation subject to certain Internal Revenue Code limitations. In addition, no participant may purchase more than 2,000 shares of common stock in each offering period. Prior to 2015, the offering periods under the 2010 ESPP are six-month periods commencing on June 1 and December 1 of each year. In January 2015, the Compensation Committee of the Company’s Board of Directors approved the change in those six-month period commencement dates to November 2 and May 2 of each year, effective November 2, 2015. The price of common stock purchased under the plan is 85 percent of the lower of the fair market value of the common stock on the commencement date and exercise date of each six -month offering period. The 2010 ESPP, as amended in 2012, provides for the issuance of a maximum of 4.3 million shares of common stock. During the twelve months ended December 31, 2015 , 761,844 shares were purchased and issued. As of December 31, 2015 , there were 1.1 million shares available for issuance. Stock Based Compensation In accordance with ASC Topic 718, stock-based compensation expense associated with stock options, RSUs, PRSUs, RSAs, and purchase rights under the 2010 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. During the years ended December 31, 2015 , 2014 , and 2013 , the Company recorded stock-based compensation expense of $13.8 million , $16.0 million and $19.9 million , respectively. The following table summarizes the weighted-average grant date fair values of the Company's stock-based awards granted in the periods indicated: Years Ended December 31, 2015 2014 2013 Stock options $ 4.56 $ 4.79 $ 4.89 RSUs $ 8.59 $ 8.72 $ 9.20 PRSUs N/A $ 9.16 $ 11.24 RSAs N/A N/A N/A ESPP $ 2.03 $ 2.46 $ 2.94 The Company values the RSUs and RSAs at the closing market price of the Company’s common stock on the date of grant. The fair value of the PRSU 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 and purchase rights under the 2010 ESPP 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 and of each employee’s purchase right under the 2010 ESPP in the periods indicated: Years Ended December 31, Stock Options 2015 2014 2013 Expected volatility 52 % 52 % 62 % Expected life (years) 6.25 6.21 6.05 Expected dividend yield — — — Risk-free interest rate 1.56 % 1.87 % 1.14 % Years Ended December 31, ESPP 2015 2014 2013 Expected volatility 46 % 45 % 50 % Expected life (years) 0.46 0.50 0.50 Expected dividend yield — — — Risk-free interest rate 0.18 % 0.07 % 0.09 % In addition, the Company applies an estimated forfeiture rate to awards granted and records stock-based compensation expense only for those awards that are expected to vest. Forfeiture rates are estimated at the time of grant based on the Company's historical experience. Further, to the extent the Company's actual forfeiture rate is different from management's estimate, stock-based compensation is adjusted accordingly. On February 22, 2011, in connection with the acquisition of Occam, the Company issued 536,190 stock options and 42,654 RSUs to certain Occam employees. The grants were in exchange for certain options and RSUs that were held by Occam employees prior to the acquisition which retained the original vesting schedule of the initial Occam grants, except for certain equity awards held by Occam executives that were accelerated in association with their severance agreements. The Company estimated the fair value of $5.8 million of the options and RSUs in accordance with ASC Topic 718. In accordance with ASC Topic 805, the Company allocated the value of $1.4 million of certain options and RSUs to consideration in the business combination with the remaining value of $4.5 million allocated to post-combination expense to be recognized over the remaining service period of the grants. As of December 31, 2015 , unrecognized stock-based compensation expenses by award type, net of estimated forfeitures, and their expected weighted-average recognition periods are summarized in the following table (in thousands). As of December 31, 2015 Stock Option RSU PRSU RSA ESPP Unrecognized stock-based compensation expense $ 3,267 $ 14,048 $ 116 $ — $ 624 Weighted-average amortization period (in years) 2.3 2.6 1.0 0.0 0.3 Common Stock Warrants Warrants to purchase convertible preferred stock that did not expire at the close of the Company’s initial public offering, in March 2010, converted to warrants to purchase common stock at the applicable conversion rate for the related preferred stock. As of December 31, 2015 , the following warrants to purchase common stock were outstanding (in thousands, except per share data): Expiration Date Exercise Price Per Share Number of Warrants Outstanding September 4, 2017 $ 19.56 15 Shares Reserved for Future Issuance The Company had common shares reserved for future issuance as follows (in thousands): As of December 31, 2015 2014 2013 Stock options outstanding 2,655 3,701 2,560 Restricted stock units outstanding 2,469 1,734 1,506 Performance restricted stock units outstanding 184 362 413 Shares available for future grant under 2010 Plan 2,749 2,283 3,652 Shares available for future issuance under ESPP 1,129 1,891 2,574 Common stock warrants 15 15 23 Total 9,201 9,986 10,728 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 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 year ended December 31, 2015 , the Company repurchased 3,540,530 shares of common stock for $27.2 million at an average price of $7.68 per share. As of December 31, 2015 , approximately $12.8 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.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plan	Employee Benefit Plan The Company sponsors a 401(k) tax-deferred savings plan for all employees who meet certain eligibility requirements. Participants may contribute, on a pre-tax basis, a percentage of their annual compensation, but not to exceed a maximum contribution amount pursuant to Section 401(k) of the Internal Revenue Code. The Company, at the discretion of the board of directors, may make additional matching contributions on behalf of the participants. The Company made matching contributions totaling $1.8 million , $1.5 million , and $1.5 million in 2015 , 2014 and 2013 , respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income	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). Year Ended December 31, 2015 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (58 ) $ 138 $ 80 Other comprehensive loss (36 ) (239 ) (275 ) Balance at end of period $ (94 ) $ (101 ) $ (195 ) Year Ended December 31, 2014 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ — $ 190 $ 190 Other comprehensive loss before reclassification adjustments (57 ) (52 ) (109 ) Reclassification adjustment for realized gains on marketable securities included in net loss (1 ) — (1 ) Other comprehensive loss (58 ) (52 ) (110 ) Balance at end of period $ (58 ) $ 138 $ 80 Year Ended December 31, 2013 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ — $ 132 $ 132 Other comprehensive income — 58 58 Balance at end of period $ — $ 190 $ 190 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 Consolidated Statements of Comprehensive Loss.

Credit Facility

Credit Facility	12 Months Ended
	Dec. 31, 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 the 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”). 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 the Company's assets, including its intellectual property. Proceeds of the credit facility may be used for general corporate purposes and permitted acquisitions. Loans under the credit facility bear interest at an annual rate equal to the base rate plus 0.75% to 1.25% or LIBOR plus 2.00% to 2.50% based on a leverage ratio of consolidated funded indebtedness to consolidated Adjusted EBITDA (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 December 31, 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. On December 23, 2015 (the “Amendment Date”), the Company entered into a First Amendment of Credit Agreement (the “First Amendment”) with Bank of America, N.A. as administrative agent and lender, which modifies the Company’s Credit Agreement dated as of July 29, 2013. The Amendment extends the maturity date of the revolving facility under the Credit Agreement from July 29, 2016 to September 30, 2018. The Amendment also modifies the definition of consolidated leverage ratio, which would apply in the event the Company makes any borrowings under the Credit Agreement, and certain other definitions and terms as described in the Amendment. As of December 31, 2015 , no revolving loans were drawn under the Credit Agreement, as amended. The Company incurred debt issuance costs that were directly attributable to the original issuance and extension of this credit facility of $0.3 million in 2013 and $0.1 million in 2015, respectively. These costs are amortized over the extended term of the credit facility. As of December 31, 2015 , the unamortized balance of debt issuance costs were $0.2 million , of which $0.1 million were included within "Prepaid expenses and other current assets" and $0.1 million were included within "Other assets" in the Company's Consolidated Balance Sheets.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The domestic and foreign components of loss before provision for (benefit from) incomes taxes were as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic $ (27,674 ) $ (21,495 ) $ (18,500 ) Foreign 1,876 1,262 1,221 Loss before provision for (benefit from) income taxes $ (25,798 ) $ (20,233 ) $ (17,279 ) The Company recorded a provision for (benefit from) income taxes of $0.5 million , $0.6 million , and $(14.0) thousand , in 2015 , 2014 and 2013 , respectively. The income tax provision for 2015 primarily consisted of state and foreign income taxes. Provision for (benefit from) income taxes consisted of the following for the periods indicated (in thousands): Years Ended December 31, 2015 2014 2013 Current: Federal $ — $ — $ (274 ) State 90 104 41 Foreign 493 469 315 Current income tax 583 573 82 Deferred: Foreign (48 ) 8 (96 ) Deferred income tax (48 ) 8 (96 ) Provision for (benefit from) income taxes $ 535 $ 581 $ (14 ) The differences between the statutory tax rate and the effective tax rate, expressed as a percentage of loss before income taxes, were as follows: Years Ended December 31, 2015 2014 2013 Federal statutory rate 34.0 % 34.0 % 34.0 % State statutory rate 2.6 % 2.5 % 3.4 % Foreign operations 1.1 % (0.1 )% 1.4 % Release of FIN 48 liability and interest — % — % 0.7 % R&D tax credits 11.2 % 9.2 % 13.1 % Foreign income inclusion (2.4 )% (0.3 )% — % Non-deductible stock compensation (1.9 )% (0.9 )% (7.3 )% Other permanent items (2.0 )% (1.5 )% 2.8 % Tax true-up (1.3 )% (0.2 )% 1.0 % Valuation allowance (43.4 )% (45.6 )% (49.0 )% Effective tax rate (2.1 )% (2.9 )% 0.1 % The significant components of the Company’s deferred tax assets and liabilities were as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 167,387 $ 166,150 Tax credit carryforwards 27,654 25,052 Depreciation and amortization 1,947 1,275 Accruals and reserves 12,427 13,810 Deferred revenue 9,822 9,930 Stock-based compensation 5,198 5,138 Other 528 498 Gross deferred tax assets 224,963 221,853 Valuation allowance (222,410 ) (212,703 ) Net deferred tax assets 2,553 9,150 Deferred tax liabilities: Intangible assets (2,229 ) (8,995 ) Other (130 ) — Gross deferred tax liabilities (2,359 ) (8,995 ) Net deferred tax assets reflected in balance sheet $ 194 $ 155 The Company classified the net deferred tax assets of $0.2 million and $0.2 million as of December 31, 2015 and 2014 , as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets, current $ — $ 785 Deferred tax assets, long-term 194 155 Deferred tax liabilities, long-term — (785 ) $ 194 $ 155 The Company elected to early adopt ASU 2015-17 prospectively on September 27, 2015, the beginning of its 2015 fourth fiscal quarter (see Note 1). In accordance with ASU 2015-17, all deferred tax assets, along with any related valuation allowance, and net of all deferred tax liabilities as of December 31, 2015 are classified in the consolidated balance sheet as long-term. As the Company elected prospective application of ASU 2015-17, prior period was not retrospectively adjusted and remain presented in accordance with the previous accounting guidance. Management reviews the recognition of deferred tax assets to determine if realization of such assets is more likely than not. The realization of the Company’s deferred tax assets is dependent upon future earnings. The Company has been in a cumulative loss position since inception, which represents a significant piece of negative evidence. Using the more likely than not criteria specified in the applicable accounting guidance, this negative evidence cannot be overcome by positive evidence currently available to the Company and as a result the Company has established a full valuation allowance against its deferred tax assets with the exception of certain foreign deferred tax assets. The Company’s valuation allowance increased by $9.7 million and $5.4 million for the years ended December 31, 2015 and 2014 , respectively. As of December 31, 2015 and 2014 , respectively, the valuation allowance included $0.1 million related to excess tax benefits of stock option deductions prior to the adoption of ASC Topic 718. The benefits will increase additional paid-in capital when realized. As of December 31, 2015 , the Company had U.S. federal and state net operating losses of approximately $552.7 million and $122.1 million , respectively. The U.S. federal net operating loss carryforwards will expire at various dates beginning in 2019 and through 2035 if not utilized. The state net operating loss carryforwards will expire at various dates beginning in 2016 and through 2035 , if not utilized. In addition, as of December 31, 2015 and 2014 , the Company had $37.8 million and $37.6 million in federal deductions, respectively, and $34.2 million and $34.0 million in state deductions, respectively, related to excess tax benefits from stock options which are not included in the net operating loss carryforward amounts in the table above since they have not met the realization criteria of ASC Topic 718. The tax benefits from these deductions will increase additional paid-in capital when realized. Additionally, the Company has U.S. federal, California and other U.S. states research and development credits of approximately $22.0 million , $25.3 million and $2.2 million as of December 31, 2015 , respectively. The U.S. federal research and development credits will begin to expire in 2020 and through 2035 , and the California research and development credits have no expiration date. The credits related to other various U.S. states will begin to expire in 2016 and through 2030. Based on current activity during 2015 , the Company does not anticipate to have further adjustments or limitations to the Company’s net operating loss carryforwards. In December 2015, President Barack Obama signed into law the Protecting Americans from Tax Hikes (PATH) Act of 2015, which makes the Section 41 research credit, which expired on December 31, 2014, a permanent provision of the Internal Revenue Code. The benefit of the reinstated credit did not impact the income statement in the period of enactment, which was the fourth quarter of 2015, as the research and development credit carryforwards are offset by a full valuation allowance. The Company recognizes deferred tax liabilities associated with outside basis differences on investments in foreign subsidiaries, unless the difference is considered essentially permanent in duration. Thus, the Company has not recorded deferred taxes on approximately $2.3 million of undistributed earnings, as they are intended to be permanently reinvested. As of December 31, 2015 , the determination of the unrecorded deferred tax liability related to these earnings is not practicable. If circumstances change and it becomes apparent that some or all of the undistributed earnings will not be invested indefinitely, or will be remitted in the foreseeable future, an additional deferred tax liability will be recorded for some or all of the outside basis difference. Uncertain Tax Positions ASC Topic 740, “Income Taxes,” prescribes a recognition threshold and measurement attribute to the financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The guidance also provides guidance on derecognition, classification, accounting in interim periods and disclosure requirements for uncertain tax positions. The standard requires the Company to recognize the financial statement effects of an uncertain tax position when it is more likely than not that such position will be sustained upon audit. The Company recognizes accrued interest and penalties related to unrecognized tax benefits as interest expense and income tax expense, respectively, in statements of comprehensive loss. The following table reconciles the Company's unrecognized tax benefits for the years ended December 31, 2015 and 2014 (in thousands): Years Ended December 31, 2015 2014 Balance at beginning of period $ 15,421 $ 14,382 Additions for tax positions related to prior year 56 76 Reductions for tax positions related to prior year (59 ) — Additions for tax positions related to current year 1,179 963 Balance at end of period $ 16,597 $ 15,421 As of December 31, 2015 and 2014 , the Company had unrecognized tax benefits of $16.6 million and $15.4 million , respectively, none of which would affect the Company's effective tax rate if recognized. There were no accrued interest or penalties for uncertain income tax as of December 31, 2015 . The Company files tax returns in the United State and various state jurisdictions, the United Kingdom, China and Brazil. The tax years 1999 through 2015 remain open and subject to examination by the appropriate governmental agencies in the U.S. due to tax attribute carryforwards.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information The Company develops, markets and sells communications access systems and software, and there are no segment managers who are held accountable for operations, operating results and plans for levels or components below the Company unit level. Accordingly, the Company is considered to be in a single reporting segment and operating unit structure. The Company’s chief operating decision maker is the Company’s Chief Executive Officer, who reviews financial information presented on a Company-wide basis, for purposes of allocating resources and evaluating financial performance. Geographic Information: The following is a summary of revenues by geographic region based upon the location of the customers (in thousands): Years Ended December 31, 2015 2014 2013 United States $ 360,077 $ 352,458 $ 333,403 Caribbean 13,358 18,725 17,466 Europe 11,090 5,948 17,397 Canada 10,198 9,995 10,231 Other 12,740 14,101 4,121 Total $ 407,463 $ 401,227 $ 382,618 The Company's property and equipment, net of accumulated depreciation, are located in the following geographical areas (in thousands): As of December 31, 2015 2014 2013 United States $ 15,362 $ 17,852 $ 14,969 China 1,787 2,292 2,504 Total $ 17,149 $ 20,144 $ 17,473

Quarterly Financial Data - Unau

Quarterly Financial Data - Unaudited	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data - Unaudited	Quarterly Financial Data—Unaudited 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 first quarter of 2015 and one more day in the fourth quarter of 2015 than in the respective 2014 periods. The following table presents selected unaudited quarterly financial data of the Company (in thousands, except per share data). The Company’s quarterly results of operations for these periods are not necessarily indicative of future results of operations. Fiscal Year 2015 Quarter Ended March 28 June 27 September 26 December 31 Revenue $ 91,038 $ 99,129 $ 112,297 $ 104,999 Gross profit 42,490 48,289 53,113 46,537 Operating income (loss) (11,887 ) (5,765 ) 877 (9,735 ) Net income (loss) (11,930 ) (5,779 ) 922 (9,546 ) Net income (loss) per common share, basic $ (0.23 ) $ (0.11 ) $ 0.02 $ (0.19 ) Net income (loss) per common share, diluted $ (0.23 ) $ (0.11 ) $ 0.02 $ (0.19 ) Fiscal Year 2014 Quarter Ended March 29 June 28 September 27 December 31 Revenue $ 85,820 $ 98,005 $ 105,769 $ 111,633 Gross profit 36,926 44,342 45,080 51,441 Operating loss (9,897 ) (3,890 ) (3,744 ) (2,853 ) Net loss (10,027 ) (3,951 ) (3,848 ) (2,988 ) Net loss per common share, basic $ (0.20 ) $ (0.08 ) $ (0.08 ) $ (0.06 ) Net loss per common share, diluted $ (0.20 ) $ (0.08 ) $ (0.08 ) $ (0.06 )

Schedule II. Valuation and Qual

Schedule II. Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2015
Valuation and Qualifying Accounts [Abstract]
Schedule II. Valuation and Qualifying Accounts	The table below summarizes the changes in allowance for doubtful accounts and product return reserve for the periods indicated (in thousands): Additions Charged to Balance Costs or Deductions at Beginning of Expenses or and Write Balance at Year Revenue Offs End of Year Year Ended December 31, 2015 Allowance for doubtful accounts $ 241 $ 405 $ (145 ) $ 501 Product return reserve 508 4,224 (4,069 ) 663 Year Ended December 31, 2014 Allowance for doubtful accounts $ 358 $ 154 $ (271 ) $ 241 Product return reserve 764 4,805 (5,061 ) 508 Year Ended December 31, 2013 Allowance for doubtful accounts $ 421 $ (13 ) $ (50 ) $ 358 Product return reserve 1,740 3,535 (4,511 ) 764

Description of Business and S22

Description of Business and Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Company	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 that are designed to enhance and transform CSP access networks to meet the changing demands of subscribers rapidly and cost-effectively.
Basis of Presentation	Basis of Presentation 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. The accompanying 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”). In the opinion of management, the consolidated 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.
Applicable Accounting Guidance	Applicable Accounting Guidance Any reference in these notes to applicable accounting guidance (“guidance”) is meant to refer to the authoritative U.S. generally accepted accounting principles ("GAAP") as found in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”).
Use of Estimates	Use of Estimates The preparation of financial statements is in conformity with U.S. GAAP, which requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. For the Company, these estimates include, but are not limited to: allowances for doubtful accounts and sales returns, excess and obsolete inventory, allowances for obligations to its contract manufacturers, valuation of stock-based compensation, useful lives assigned to long-lived assets and acquired intangible assets, standard and extended warranty costs, and contingencies. Actual results could differ from those estimates, and such differences could be material to the Company's financial position and results of operations.
Revenue Recognition	Revenue Recognition The Company derives revenue primarily from the sale of hardware products and related software. Revenue is recognized when all of the following criteria have been met: • Persuasive evidence of an arrangement exists. The Company generally relies upon sales agreements and customer purchase orders as evidence of an arrangement. • Delivery has occurred. The Company uses the shipping terms of the arrangement or evidence of customer acceptance to verify delivery or performance. • Sales price is fixed or determinable. The Company assesses whether the sales price is fixed or determinable based on the payment terms and whether the sales price is subject to refund or adjustment. Payment terms to customers can range from net 30 to net 120 days. • Collectability is reasonably assured. The Company assesses collectability based primarily on creditworthiness of customers and their payment histories. Revenue from installation and training services are recognized as the services are completed. Post-sales software support revenue and extended warranty services revenue are deferred and recognized ratably over the period during which the services are to be performed. In instances where substantive acceptance provisions are specified in the customer agreement, revenue is deferred until all acceptance criteria have been met. From time to time, the Company offers customers sales incentives, which include volume rebates and discounts. These amounts are estimated on a quarterly basis and recorded as a reduction of revenue. The Company enters into arrangements with certain of its customers who receive government supported loans and grants from the U.S. Department of Agriculture's Rural Utility Service (“RUS”) to finance capital spending. Under the terms of an RUS equipment contract that includes installation services, the customer does not take possession and control and title does not pass until formal acceptance is obtained from the customer. Under this type of arrangement, the Company does not recognize revenue until it has received formal acceptance from the customer. For RUS arrangements that do not involve installation services, the Company recognizes revenue in accordance with the revenue recognition policy described above. The Company's products contain both software and non-software components that function together to deliver the products' essential functionality. When the Company enters into sales arrangements that consist of multiple deliverables of its product and service offerings, the Company allocates the total consideration of the arrangement to each separable deliverable based on its relative selling price. The Company limits the amount allocable to delivered elements to the amount that is not contingent upon the delivery of additional items or meeting specified performance conditions, and recognizes revenue on each deliverable in accordance with its revenue recognition policy. The determination of selling price for each deliverable is based on a selling price hierarchy, which is vendor-specific objective evidence (“VSOE”) if available, third-party evidence (“TPE”) if VSOE is not available, or estimated selling price (“ESP”) if neither VSOE nor TPE is available. VSOE of selling price is based on the price charged when the element is sold separately. In determining VSOE, the Company requires that a substantial majority of the selling prices of an element fall within a narrow range when each element is sold separately. The Company has established VSOE for its training and post-sales software support services based on the normal pricing practices of these services when sold separately. TPE of selling price is established by evaluating whether there are similar competitor products or services that are sold in stand-alone sales transaction to similarly situated customers. Generally, the Company's marketing strategy differs from that of its peers and its offerings contain a significant level of customization and differentiation such that the comparable pricing of products with similar functionality cannot be obtained. Additionally, as the Company is unable to reliably determine what similar competitor products' selling prices are on a stand-alone basis, it is not typically able to determine TPE. ESP is established considering multiple factors including, but not limited to geographies market conditions, competitive landscape, internal costs, gross margin objectives, characteristics of targeted customers and pricing practices. The determination of ESP is made through consultation with and formal approval by management, taking into consideration the go-to-market strategy.
Cost of Revenue	Cost of Revenue Cost of revenue consists primarily of finished goods inventory purchased from the Company’s contract manufacturers, payroll and related expenses associated with managing the relationships with contract manufacturers, depreciation of manufacturing test equipment, warranty costs, excess and obsolete inventory costs, shipping charges, and amortization of certain intangible assets.
Warranty	Warranty The Company offers limited warranties for its hardware products for a period of one , three or five years, depending on the product type. Warranty service revenues are deferred and recognized ratably over the period during which the services are to be performed. The Company recognizes estimated costs related to warranty activities as a component of cost of revenue upon product shipment or upon identification of a specific product failure. The estimates are based upon historical and projected product failure and claim rates, historical costs incurred in correcting product failures and information available related to any specifically identified product failures. The recorded amount is adjusted from time to time for specifically identified warranty exposure. Actual warranty expenses are charged against the Company’s estimated warranty liability when incurred. Factors that affect the Company’s warranty liability include the number of installed units and historical and anticipated rates of warranty claims and cost per claim.
Stock-Based Compensation	Stock-Based Compensation In accordance with ASC Topic 718, “ Compensation - Stock Compensation ” (“ASC Topic 718”), stock-based awards are recorded at fair value as of the grant date and recognized to expense over the employee’s requisite service period (generally the vesting period), which the Company has elected to amortize on a straight-line basis. Stock-based compensation expense is reduced by the Company’s estimated forfeitures on all unvested awards. The fair value of stock option and employee stock purchase right is estimated at the grant date using the Black-Scholes option valuation model. The fair value of restricted stock unit and restricted stock award is based on the closing market price of the Company's common stock on the date of grant. The fair value of performance restricted stock unit (“PRSU”) with a market condition is estimated on the date of grant, using a Monte Carlo simulation model to estimate the total return ranking 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.
Research and Development	Research and Development Research and development costs include costs of developing new products and processes, as well as design and engineering costs. Such costs are charged to research and development expense as incurred. Development costs related to software incorporated in the Company’s products incurred subsequent to the establishment of technological feasibility are capitalized and amortized over the estimated useful lives of the related products. Technological feasibility is established upon completion of a working model.
Contingencies	Contingencies From time to time, the Company is involved in legal proceedings arising from the normal course of business activities. The Company evaluates the likelihood of an unfavorable outcome of legal proceedings to which it is a party and accrues a loss contingency when the loss is probable and reasonably estimable. Assessing legal contingencies involves significant judgment and estimates and the outcome of litigation is inherently uncertain and subject to numerous factors outside the Company's control. Significant judgment is required when the Company assesses the likelihood of any adverse judgments or outcomes, including the potential range of possible losses, and whether losses are probable and reasonably estimable. The Company offers limited warranties for its hardware products for a period of one , three or five years, depending on the product type. The Company estimates costs related to warranty activities based upon historical and projected product failure and claim rates, historical costs incurred in correcting product failures and information available related to any specifically identified product failures. The Company recognizes estimated warranty costs when it is probable that a liability has been incurred and the amount of loss is reasonably estimable. Significant judgment is required in estimating costs associated with warranty activities and the Company estimates are limited to information available to the Company at the time of such estimates. In some cases, such as when a specific product failure is first identified or a new product is introduced, the Company may initially have limited information and limited historical failure and claim rates upon which to base its estimates, and such estimates may require revision in future periods. Because of uncertainties related to these matters, the Company bases its estimates of whether a loss contingency is probable or reasonably possible, as well as the reasonable range of possible losses associated with each loss contingency, only on the information available at the time. As additional information becomes available, and at least quarterly, the Company reassesses the potential liability on each significant matter and may revise its estimates. These revisions could have a material impact on the Company's business, operating results or financial condition. The actual outcome of these legal proceedings may materially differ from the Company's estimates of potential liability, which could have a material adverse effect on the Company's business, operating results or financial condition.
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.
Credit Risk and Inventory Supplier Concentrations	Credit Risk and Inventory Supplier Concentrations Financial instruments that potentially subject the Company to significant concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. Cash equivalents consist of money market funds, which are invested through financial institutions in the United States. Deposits in these financial institutions may, at times, exceed federally insured limits. The Company has not experienced any losses in such accounts. The Company also has approximately $5.4 million of cash held by its foreign subsidiaries in Brazil, China and the United Kingdom. Management believes that the financial institutions that hold the Company’s cash and cash equivalents are financially sound and, accordingly, minimal credit risk exists with respect to these cash and cash equivalents. Concentrations of credit risk in relation to customer with an accounts receivable balance of 10% or greater of total accounts receivable and customer with net revenues of 10% or greater of total revenues are presented below for the periods indicated. Percentage of Accounts Receivable Percentage of Revenue At December 31, Years Ended December 31, 2015 2014 2015 2014 2013 CenturyLink 27% * 22% 23% 26% * Less than 10% of total accounts receivable. The Company maintains an allowance for doubtful accounts for estimated losses resulting from the inability of its customers to make required payments. The Company records a specific allowance based on an analysis of individual past-due balances. Additionally, based on its historical write-offs and collections experience, the Company records an additional allowance based on a percentage of outstanding receivables. The Company performs credit evaluations of its customers’ financial condition. These evaluations require significant judgment and are based on a variety of factors including, but not limited to, current economic trends, payment history and financial review of the customer. Actual collection losses may differ from management’s estimates, and such differences could be material to the Company’s financial position and results of operations. The Company depends primarily on a small number of outside contract manufacturers for the bulk of its finished goods inventory. In particular, the Company relies on Flextronics for the manufacture of a large percentage of its products. The Company generally purchases its products through purchase orders with its suppliers or contract manufacturers. While the Company seeks to maintain a sufficient reserve of its products, the Company’s business and results of operations could be adversely affected by a stoppage or delay in receiving such products, the receipt of defective parts, an increase in price of such products or the Company’s inability to obtain lower prices from its contract manufacturers and suppliers in response to competitive pressures.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of cash and cash equivalents, marketable securities, trade receivables, accounts payable, and other accrued liabilities approximate their fair value due to their relatively short-term nature.
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 and marketable securities are stated at amounts that approximate fair value based on quoted market prices. 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 comprehensive 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 to results of operations as other income (expense).
Restricted Cash	Restricted Cash As of December 31, 2014, the Company had $0.3 million cash restricted for collateralizing the outstanding letters of credit with Silicon Valley Bank, which restriction was subsequently released during the first quarter of 2015.
Inventory	Inventory Valuation Inventory, which primarily consists of finished goods purchased from contract manufacturers, is stated at the lower of cost, determined by the first-in, first-out method, or market value. Inbound shipping costs are included in cost of inventory. In addition, the Company, from time to time, procures component inventory primarily as a result of manufacturing discontinuation of critical components by suppliers. The Company regularly monitors inventory quantities on hand and records write-downs for excess and obsolete inventories based on the Company’s estimate of demand for its products, potential obsolescence of technology, product life cycles, and whether pricing trends or forecasts indicate that the carrying value of inventory exceeds its estimated selling price. These factors are impacted by market and economic conditions, technology changes, and new product introductions and require estimates that may include elements that are uncertain. Actual demand may differ from forecasted demand and may have a material effect on gross margins. If inventory is written down, a new cost basis is established that cannot be increased in future periods. Shipments from our suppliers or contract manufacturers before the Company receives them are recorded as in-transit inventory when title and the significant risks and rewards of ownership have passed to the Company.
Deferred Revenue and Deferred Cost of Revenue	Deferred Revenue and Deferred Cost of Revenue Deferred revenue results from transactions where the Company billed the customer for product shipped or services performed but not all revenue recognition criteria have been met. When the Company’s products have been shipped, but the product revenue associated with the arrangement has been deferred as a result of not meeting the criteria for immediate revenue recognition, the Company also defers the related inventory costs for the delivered items until all criteria are met for revenue recognition. The Company defers tangible direct costs associated with hardware products delivered based on the inventory cost at the time of shipment. Certain costs directly related to the delivery of professional services that cannot be accounted for separately from the undelivered items included in a multiple element arrangement are also capitalized and deferred, if deemed recoverable, until all revenue recognition criteria are met. Accordingly, all cost of services incurred directly related to the delivery of an inseparable professional service item in which revenue has not yet been recognized are deferred and recorded within "Deferred cost of revenue" in the Company's Consolidated Balance Sheets. We evaluate deferred cost of revenue for recoverability based on multiple factors, including whether net revenues will exceed the amount of deferred cost of revenue based on the terms of the overall arrangement. To the extent that deferred cost of revenue is determined to be unrecoverable, we adjust deferred cost of revenue with a charge to cost of revenue in the current period. In connection with our recoverability assessments, we have not incurred significant impairment charges through December 31, 2015 . We recognize deferred revenue and associated deferred cost of revenue, as revenue and cost of revenue respectively, in the Consolidated Statements of Comprehensive Loss once all revenue recognition criteria have been met.
Property and Equipment	Property and Equipment Property and equipment are stated at cost, less accumulated depreciation, and are depreciated using the straight-line method over the estimated useful life of each asset. Computer equipment is depreciated over two years; purchased software is depreciated over three years; test equipment is depreciated over three years; furniture and fixtures are depreciated over seven years; and leasehold improvements are depreciated over the shorter of the respective lease term or the estimated useful life of the asset. Maintenance and repairs are charged to expense as incurred.
Goodwill	Goodwill The Company records goodwill when consideration paid in a business acquisition exceeds the fair value of the net tangible assets and the identified intangible assets acquired. Goodwill is not amortized but instead is subject to an annual impairment test or more frequently if events or changes in circumstances indicate that it may be impaired. The Company evaluates goodwill on an annual basis as of the end of the second quarter of each fiscal year. Management has determined that it operates as a single reporting unit and, therefore, evaluates goodwill impairment at the enterprise level. In an annual impairment test, the Company first assesses qualitative factors to determine whether it is necessary to perform the two-step quantitative goodwill impairment test. In assessing the qualitative factors, management considers 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. If the Company determines as a result of the qualitative assessment that it is more likely than not (that is, a likelihood of more than 50 percent) that the fair value of a reporting unit is less than its carrying amount, then the quantitative test is required. Otherwise, no further testing is required. In a quantitative test, the Company compares its fair value to its carrying value including goodwill. The Company determines its fair value using both an income approach and a market approach. Under the income approach, the Company determines fair value based on estimated future cash flows, discounted by an estimated weighted-average cost of capital, which reflects the overall level of inherent risk of the Company and the rate of return an outside investor would expect to earn. Under the market-based approach, the Company utilizes information regarding the Company as well as publicly available industry information to determine earnings multiples that are used to value the Company. If the carrying value of the Company exceeds its fair value, the Company will determine the amount of impairment loss by comparing the implied fair value of goodwill with the carrying value of goodwill. An impairment charge is recognized for the excess of the carrying value of goodwill over its implied fair value. At the end of the second quarter of 2015 , the Company has completed its annual goodwill impairment test. Based on its assessment of the above qualitative factors, 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 quantitative goodwill impairment test at the time. There have been no significant events or changes in circumstances subsequent to the 2015 annual impairment test that would more likely than not indicate that the carrying value of goodwill may have been impaired as of December 31, 2015 . Therefore, there was no impairment to the carrying value of the Company's goodwill as of December 31, 2015 . As described above, the Company’s estimate of its fair value depends upon a number of qualitative and quantitative factors. Although the Company has concluded that there was no impairment to the carrying value of goodwill as of December 31, 2015 , the Company’s stock price and market capitalization have declined since December 31, 2015 . The estimated fair value of the Company exceeded carrying value by approximately $154.7 million or 59% , and $153.8 million or 65% , using the market capitalization on the annual impairment testing date and December 31, 2015 , respectively. If the Company will experience a sustained decline in its stock price and market capitalization, or if the Company’s stock price will decline below its book value, the estimated fair value of the Company would be negatively impacted, and the Company would be required to reassess possible impairment of the carrying value of our goodwill. There were no impairment losses for goodwill during 2014 and 2013 .
Intangible Assets and Other Long-Lived Assets	Intangible Assets and Other Long-Lived Assets Intangible assets with finite useful lives are amortized over their estimated useful life. The Company periodically evaluates long-lived assets, including intangible assets, for impairment whenever events or changes in circumstances indicate that a potential impairment may have occurred. If such events or changes in circumstances arise, the Company compares the carrying amount of the long-lived assets to the estimated future undiscounted cash flows expected to be generated by the long-lived assets. If the estimated aggregate undiscounted cash flows are less than the carrying amount of the long-lived assets, an impairment charge, calculated as the amount by which the carrying amount of the assets exceeds the fair value of the assets, is recorded. The fair value of long-lived assets is determined based on the estimated discounted cash flows expected to be generated from the assets. The Company has reviewed events and changes to its business during the year and has determined that there was no impairment to its intangible assets and other long-lived assets during 2015 . The Company did not incur any impairment losses for intangible assets and other long-lived assets during 2014 and 2013 .
Income Taxes	Income Taxes The Company evaluates its tax positions and estimates its current tax exposure along with assessing temporary differences that result from different book to tax treatment of items not currently deductible for tax purposes. These differences result in deferred tax assets and liabilities on the Company’s balance sheets, which are estimated based upon the difference between the financial statement and tax bases of assets and liabilities using the enacted tax rates that will be in effect when these differences reverse. In general, deferred tax assets represent future tax benefits to be received when certain expenses previously recognized in the Company’s statements of operations become deductible expenses under applicable income tax laws or loss or credit carryforwards are utilized. Accordingly, realization of the Company’s deferred tax assets is dependent on future taxable income against which these deductions, losses and credits can be utilized. The Company must assess the likelihood that the Company’s deferred tax assets will be recovered from future taxable income, and to the extent the Company believes that recovery is not more likely than not, the Company must establish a valuation allowance. Management judgment is required in determining the Company’s provision for income taxes, the Company’s deferred tax assets and liabilities and any valuation allowance recorded against the Company’s net deferred tax assets. Excluding our foreign operations, the Company recorded a full valuation allowance at each balance sheet date presented because, based on the available evidence, the Company believes it is more likely than not that it will not be able to utilize all of its deferred tax assets in the future. The Company intends to maintain the full valuation allowances until sufficient evidence exists to support the reversal of the valuation allowances.
Foreign Currency Translation	Foreign Currency Translation Assets and liabilities of the Company’s wholly owned foreign subsidiaries are translated from their respective functional currencies at exchange rates in effect at the balance sheet date, and revenues and expenses are translated at the monthly average exchanges rates. Translation adjustments are reflected as a separate component of stockholders’ equity. Realized foreign currency transaction gains and losses were not significant during the years ended December 31, 2015 , 2014 , and 2013 .
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2015, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update No. 2015-17, Balance Sheet Classification of Deferred Taxes ("ASU 2015-17"), which requires the presentation of deferred income tax assets and deferred income tax liabilities, along with any related valuation allowance, as non-current in a classified balance sheet instead of the current GAAP requirement to separate deferred income tax assets and liabilities into current and non-current amounts. The current GAAP requirement that deferred income tax assets and liabilities of a tax-paying component of an entity be offset and presented as a single amount is not affected by the amendments in this accounting standard update. ASU 2015-17 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted either prospectively or retrospectively as of the beginning of any interim or annual reporting period. The Company elected to early adopt this accounting standard update prospectively on September 27, 2015, the beginning of its 2015 fourth fiscal quarter. As the Company elected prospective application of ASU 2015-17, prior period was not retrospectively adjusted and remain presented in accordance with the previous accounting guidance. The adoption of this accounting standard update has no material impact in the Company’s consolidated financial statements. In July 2015, the FASB issued Accounting Standards Update No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory ("ASU 2015-11"), which requires measurement of inventory at lower of cost and net realizable value, versus lower of cost or market. Net realizable value is the estimated selling price in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. ASU 2015-11 will be effective for the Company beginning in the first quarter of fiscal 2017. Early application is permitted, and the guidance should be applied prospectively. The Company is currently assessing the potential impact of adopting this new guidance on its consolidated financial statements. In May 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606) ("ASU 2014-09"), which provides guidance for revenue recognition. ASU 2014-09 supersedes the revenue recognition requirements in Topic 605, Revenue Recognition, and most industry-specific guidance. Additionally, it supersedes some cost guidance included in Subtopic 605-35, Revenue Recognition-Construction-Type and Production-Type Contracts, and creates new Subtopic 340-40, Other Assets and Deferred Costs-Contracts with Customers. The standard’s core principle is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In doing so, companies will need to use more judgment and make more estimates than under the previous guidance. These may include identifying performance obligations in the contract, estimating the amount of variable consideration to include in the transaction price and allocating the transaction price to each separate performance obligation. On August 12, 2015, the FASB issued Accounting Standards Update No. 2015-14, Revenue from Contracts with Customers (Topic 606), Deferral of the Effective Date ("ASU 2015-14") to defer the effective date of ASU 2014-09 by one year. As a result, the standard will be effective for the Company in the first quarter of fiscal 2018. ASU 2015-14 permits early adoption of the new revenue standard, but not before its original effective date. The Company is currently assessing the method of adoption and the potential impact of adopting this new guidance on its consolidated financial statements.

Description of Business and S23

Description of Business and Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Schedule of Customer Concentration Risk	Concentrations of credit risk in relation to customer with an accounts receivable balance of 10% or greater of total accounts receivable and customer with net revenues of 10% or greater of total revenues are presented below for the periods indicated. Percentage of Accounts Receivable Percentage of Revenue At December 31, Years Ended December 31, 2015 2014 2015 2014 2013 CenturyLink 27% * 22% 23% 26% * Less than 10% of total accounts receivable.

Cash, Cash Equivalents and Ma24

Cash, Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Summary of cash and cash equivalents	Cash, cash equivalents and marketable securities consisted of the following (in thousands): December 31, December 31, Cash and cash equivalents: Cash $ 13,378 $ 17,866 Money market funds 10,248 30,963 Total cash and cash equivalents 23,626 48,829 Marketable securities: Corporate debt securities 35,799 61,050 U.S. government agency securities 10,520 — Commercial paper 3,645 1,800 Total marketable securities 49,964 62,850 Total cash, cash equivalents and marketable securities $ 73,590 $ 111,679
Amortized cost and fair value of marketable securities	The amortized cost and fair value of marketable securities as of December 31, 2015 were as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Corporate debt securities $ 35,869 $ 2 $ (72 ) $ 35,799 U.S. government agency securities 10,544 — (24 ) 10,520 Commercial paper 3,645 — — 3,645 Total marketable securities $ 50,058 $ 2 $ (96 ) $ 49,964 The amortized cost and fair value of marketable securities as of December 31, 2014 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 December 31, 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 $ 38,714 $ 38,651 Due in 1-2 years 11,344 11,313 Total marketable securities $ 50,058 $ 49,964

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 as of December 31, 2015 and 2014 , based on the three-tier fair value hierarchy (in thousands): As of December 31, 2015 Level 1 Level 2 Total Money market funds $ 10,248 $ — $ 10,248 Corporate debt securities — 35,799 35,799 U.S. government agency securities — 10,520 10,520 Commercial paper — 3,645 3,645 Total $ 10,248 $ 49,964 $ 60,212 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)	12 Months Ended
	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Summary of intangible assets	The details of intangible assets as of December 31, 2015 and 2014 are disclosed in the following table (in thousands): December 31, 2015 December 31, 2014 Gross Accumulated Net Gross Carrying Amount Accumulated Amortization Net Core developed technology $ 68,964 $ (64,047 ) $ 4,917 $ 68,964 $ (55,694 ) $ 13,270 Customer relationships 54,740 (53,039 ) 1,701 54,740 (42,831 ) 11,909 Total intangible assets, excluding goodwill $ 123,704 $ (117,086 ) $ 6,618 $ 123,704 $ (98,525 ) $ 25,179
Summary of expected future amortization	Expected future amortization expense for the fiscal years indicated is as follows (in thousands): Period Expected Amortization Expense 2016 5,805 2017 813 Total $ 6,618

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Accounts Receivable, net, Details	Accounts receivable, net consisted of the following (in thousands): December 31, December 31, Accounts receivable $ 48,319 $ 31,493 Allowance for doubtful accounts (501 ) (241 ) Product return reserve (663 ) (508 ) Accounts receivable, net $ 47,155 $ 30,744
Changes In Allowance For Doubtful Accounts And Product Reserve	The table below summarizes the changes in allowance for doubtful accounts and product return reserve for the periods indicated (in thousands): Additions Charged to Balance Costs or Deductions at Beginning of Expenses or and Write Balance at Year Revenue Offs End of Year Year Ended December 31, 2015 Allowance for doubtful accounts $ 241 $ 405 $ (145 ) $ 501 Product return reserve 508 4,224 (4,069 ) 663 Year Ended December 31, 2014 Allowance for doubtful accounts $ 358 $ 154 $ (271 ) $ 241 Product return reserve 764 4,805 (5,061 ) 508 Year Ended December 31, 2013 Allowance for doubtful accounts $ 421 $ (13 ) $ (50 ) $ 358 Product return reserve 1,740 3,535 (4,511 ) 764
Inventory Details	Inventory consisted of the following (in thousands): December 31, December 31, Raw materials $ 2,209 $ 3,180 Finished goods 45,458 43,573 Total inventory $ 47,667 $ 46,753
Property and Equipment, net, Details	Property and equipment, net consisted of the following (in thousands): December 31, December 31, Test equipment $ 39,035 $ 40,766 Computer equipment and purchased software 27,736 30,355 Furniture and fixtures 1,833 1,852 Leasehold improvements 6,554 6,550 Total 75,158 79,523 Accumulated depreciation and amortization (58,009 ) (59,379 ) Property and equipment, net $ 17,149 $ 20,144
Accrued Liabilities Details	Accrued liabilities consisted of the following (in thousands): December 31, December 31, Accrued compensation and related benefits $ 13,809 $ 15,782 Accrued warranty 9,564 9,553 Accrued professional and consulting fees 2,813 5,860 Advance customer payments 1,094 364 Accrued excess and obsolete inventory at contract manufacturers 1,011 888 Accrued non income related taxes 905 581 Accrued customer rebates 784 851 Accrued business travel expenses 580 1,414 Accrued freight 486 303 Accrued hosting services 466 235 Accrued rent 381 412 Income taxes payable 322 269 Accrued other 3,297 2,931 Total accrued liabilities $ 35,512 $ 39,443
Deferred Revenue Details	Deferred revenue consisted of the following (in thousands): December 31, 2015 December 31, 2014 Current: Product and services $ 8,937 $ 9,753 Extended warranty 3,187 2,969 12,124 12,722 Non-current: Product and services 58 182 Extended warranty 19,511 19,211 19,569 19,393 Total deferred revenue $ 31,693 $ 32,115

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum payments under the non-cancelable operating leases consisted of the following as of December 31, 2015 (in thousands): Period Minimum Future Lease Payments 2016 $ 2,666 2017 2,594 2018 2,325 2019 579 2020 222 Thereafter 248 Total $ 8,634
Schedule of Product Warranty Liability	Changes in the Company’s warranty reserve in the periods as indicated were as follows (in thousands): Years Ended December 31, 2015 2014 2013 Balance at beginning of period $ 9,553 $ 10,856 $ 11,762 Warranty charged to cost of revenue 4,661 3,394 4,350 Utilization of warranty (4,115 ) (3,328 ) (4,786 ) Adjustments to pre-existing warranty (535 ) (1,369 ) (470 ) Balance at end of period $ 9,564 $ 9,553 $ 10,856

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Schedule of net loss per share	The following table sets forth the computation of basic and diluted net loss per share for the periods indicated (in thousands, except per share data): Years Ended December 31, 2015 2014 2013 Numerator: Net loss $ (26,333 ) $ (20,814 ) $ (17,265 ) Denominator: Weighted-average common shares outstanding 51,489 50,808 49,419 Basic and diluted net loss per common share $ (0.51 ) $ (0.41 ) $ (0.35 ) Potentially dilutive shares, weighted-average 6,120 5,020 5,308

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders' Equity Note [Abstract]
Schedule of Stock Options Activity	The following table summarizes the activity of stock options under the Company’s equity incentive plans (in thousands, except per share data): Weighted- Weighted-Average Average Remaining Aggregate Number of Exercise Price Contractual Life Intrinsic Stock Options Shares Per Share (in years) Value (1) Outstanding as of December 31, 2014 3,701 $ 11.38 Granted 200 8.91 Exercised (97 ) 6.56 Forfeited (1,043 ) 10.07 Expired (106 ) 13.29 Outstanding as of December 31, 2015 2,655 $ 11.81 6.7 $ 250 Vested and expected to vest as of December 31, 2015 2,594 $ 11.89 6.6 $ 250 Options exercisable as of December 31, 2015 1,822 $ 13.32 5.9 $ 240 (1) Amounts represent the difference between the exercise price and the fair market value of common stock at December 31, 2015 for all in the money options outstanding.
Schedule of Restricted Stock and Restricted Stock Units Activity	The following table summarizes the activities of the Company's RSUs, PRSUs, and RSAs under the Company’s equity incentive plans (in thousands, except per share data): RSUs PRSUs RSAs Weighted-Average Weighted-Average Weighted-Average Grant Date Grant Date Grant Date Number of Fair Value Number of Fair Value Number of Fair Value Shares Per Share Shares Per Share Shares Per Share Outstanding at December 31, 2014 1,734 $ 9.53 362 $ 10.53 62 $ 21.67 Granted 1,608 8.59 — — — — Vested (706 ) 10.56 (148 ) 11.60 (62 ) 21.67 Canceled (167 ) 9.23 (30 ) 13.33 — — Outstanding at December 31, 2015 2,469 $ 8.64 184 $ 9.21 — $ —
Schedule of Grant Date Fair Values	The following table summarizes the weighted-average grant date fair values of the Company's stock-based awards granted in the periods indicated: Years Ended December 31, 2015 2014 2013 Stock options $ 4.56 $ 4.79 $ 4.89 RSUs $ 8.59 $ 8.72 $ 9.20 PRSUs N/A $ 9.16 $ 11.24 RSAs N/A N/A N/A ESPP $ 2.03 $ 2.46 $ 2.94
Valuation Assumptions, Stock Options	The following table summarizes the weighted-average assumptions used in estimating the grant-date fair value of stock options and of each employee’s purchase right under the 2010 ESPP in the periods indicated: Years Ended December 31, Stock Options 2015 2014 2013 Expected volatility 52 % 52 % 62 % Expected life (years) 6.25 6.21 6.05 Expected dividend yield — — — Risk-free interest rate 1.56 % 1.87 % 1.14 %
Valuation Assumptions, ESPP	Years Ended December 31, ESPP 2015 2014 2013 Expected volatility 46 % 45 % 50 % Expected life (years) 0.46 0.50 0.50 Expected dividend yield — — — Risk-free interest rate 0.18 % 0.07 % 0.09 %
Schedule of Unrecognized Compensation Cost	As of December 31, 2015 , unrecognized stock-based compensation expenses by award type, net of estimated forfeitures, and their expected weighted-average recognition periods are summarized in the following table (in thousands). As of December 31, 2015 Stock Option RSU PRSU RSA ESPP Unrecognized stock-based compensation expense $ 3,267 $ 14,048 $ 116 $ — $ 624 Weighted-average amortization period (in years) 2.3 2.6 1.0 0.0 0.3
Schedule of Warrants	As of December 31, 2015 , the following warrants to purchase common stock were outstanding (in thousands, except per share data): Expiration Date Exercise Price Per Share Number of Warrants Outstanding September 4, 2017 $ 19.56 15
Shares Reserved For Future Issuance	The Company had common shares reserved for future issuance as follows (in thousands): As of December 31, 2015 2014 2013 Stock options outstanding 2,655 3,701 2,560 Restricted stock units outstanding 2,469 1,734 1,506 Performance restricted stock units outstanding 184 362 413 Shares available for future grant under 2010 Plan 2,749 2,283 3,652 Shares available for future issuance under ESPP 1,129 1,891 2,574 Common stock warrants 15 15 23 Total 9,201 9,986 10,728

Accumulated Other Comprehensi31

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Schedule of 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). Year Ended December 31, 2015 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ (58 ) $ 138 $ 80 Other comprehensive loss (36 ) (239 ) (275 ) Balance at end of period $ (94 ) $ (101 ) $ (195 ) Year Ended December 31, 2014 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ — $ 190 $ 190 Other comprehensive loss before reclassification adjustments (57 ) (52 ) (109 ) Reclassification adjustment for realized gains on marketable securities included in net loss (1 ) — (1 ) Other comprehensive loss (58 ) (52 ) (110 ) Balance at end of period $ (58 ) $ 138 $ 80 Year Ended December 31, 2013 Unrealized Gains and Losses on Available-for-Sale Marketable Securities Foreign Currency Translation Adjustments Total Balance at beginning of period $ — $ 132 $ 132 Other comprehensive income — 58 58 Balance at end of period $ — $ 190 $ 190

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The domestic and foreign components of loss before provision for (benefit from) incomes taxes were as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic $ (27,674 ) $ (21,495 ) $ (18,500 ) Foreign 1,876 1,262 1,221 Loss before provision for (benefit from) income taxes $ (25,798 ) $ (20,233 ) $ (17,279 )
Schedule of Components of Income Tax Expense (Benefit)	Provision for (benefit from) income taxes consisted of the following for the periods indicated (in thousands): Years Ended December 31, 2015 2014 2013 Current: Federal $ — $ — $ (274 ) State 90 104 41 Foreign 493 469 315 Current income tax 583 573 82 Deferred: Foreign (48 ) 8 (96 ) Deferred income tax (48 ) 8 (96 ) Provision for (benefit from) income taxes $ 535 $ 581 $ (14 )
Schedule of Effective Income Tax Rate Reconciliation	The differences between the statutory tax rate and the effective tax rate, expressed as a percentage of loss before income taxes, were as follows: Years Ended December 31, 2015 2014 2013 Federal statutory rate 34.0 % 34.0 % 34.0 % State statutory rate 2.6 % 2.5 % 3.4 % Foreign operations 1.1 % (0.1 )% 1.4 % Release of FIN 48 liability and interest — % — % 0.7 % R&D tax credits 11.2 % 9.2 % 13.1 % Foreign income inclusion (2.4 )% (0.3 )% — % Non-deductible stock compensation (1.9 )% (0.9 )% (7.3 )% Other permanent items (2.0 )% (1.5 )% 2.8 % Tax true-up (1.3 )% (0.2 )% 1.0 % Valuation allowance (43.4 )% (45.6 )% (49.0 )% Effective tax rate (2.1 )% (2.9 )% 0.1 %
Schedule of Deferred Tax Assets and Liabilities	The significant components of the Company’s deferred tax assets and liabilities were as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 167,387 $ 166,150 Tax credit carryforwards 27,654 25,052 Depreciation and amortization 1,947 1,275 Accruals and reserves 12,427 13,810 Deferred revenue 9,822 9,930 Stock-based compensation 5,198 5,138 Other 528 498 Gross deferred tax assets 224,963 221,853 Valuation allowance (222,410 ) (212,703 ) Net deferred tax assets 2,553 9,150 Deferred tax liabilities: Intangible assets (2,229 ) (8,995 ) Other (130 ) — Gross deferred tax liabilities (2,359 ) (8,995 ) Net deferred tax assets reflected in balance sheet $ 194 $ 155 The Company classified the net deferred tax assets of $0.2 million and $0.2 million as of December 31, 2015 and 2014 , as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets, current $ — $ 785 Deferred tax assets, long-term 194 155 Deferred tax liabilities, long-term — (785 ) $ 194 $ 155
Unrecognized Tax Benefits Activity	The following table reconciles the Company's unrecognized tax benefits for the years ended December 31, 2015 and 2014 (in thousands): Years Ended December 31, 2015 2014 Balance at beginning of period $ 15,421 $ 14,382 Additions for tax positions related to prior year 56 76 Reductions for tax positions related to prior year (59 ) — Additions for tax positions related to current year 1,179 963 Balance at end of period $ 16,597 $ 15,421

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Revenue by Geographic Region	The following is a summary of revenues by geographic region based upon the location of the customers (in thousands): Years Ended December 31, 2015 2014 2013 United States $ 360,077 $ 352,458 $ 333,403 Caribbean 13,358 18,725 17,466 Europe 11,090 5,948 17,397 Canada 10,198 9,995 10,231 Other 12,740 14,101 4,121 Total $ 407,463 $ 401,227 $ 382,618
Property and Equipment by Geographic Region	The Company's property and equipment, net of accumulated depreciation, are located in the following geographical areas (in thousands): As of December 31, 2015 2014 2013 United States $ 15,362 $ 17,852 $ 14,969 China 1,787 2,292 2,504 Total $ 17,149 $ 20,144 $ 17,473

Quarterly Financial Data - Un34

Quarterly Financial Data - Unaudited (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following table presents selected unaudited quarterly financial data of the Company (in thousands, except per share data). The Company’s quarterly results of operations for these periods are not necessarily indicative of future results of operations. Fiscal Year 2015 Quarter Ended March 28 June 27 September 26 December 31 Revenue $ 91,038 $ 99,129 $ 112,297 $ 104,999 Gross profit 42,490 48,289 53,113 46,537 Operating income (loss) (11,887 ) (5,765 ) 877 (9,735 ) Net income (loss) (11,930 ) (5,779 ) 922 (9,546 ) Net income (loss) per common share, basic $ (0.23 ) $ (0.11 ) $ 0.02 $ (0.19 ) Net income (loss) per common share, diluted $ (0.23 ) $ (0.11 ) $ 0.02 $ (0.19 ) Fiscal Year 2014 Quarter Ended March 29 June 28 September 27 December 31 Revenue $ 85,820 $ 98,005 $ 105,769 $ 111,633 Gross profit 36,926 44,342 45,080 51,441 Operating loss (9,897 ) (3,890 ) (3,744 ) (2,853 ) Net loss (10,027 ) (3,951 ) (3,848 ) (2,988 ) Net loss per common share, basic $ (0.20 ) $ (0.08 ) $ (0.08 ) $ (0.06 ) Net loss per common share, diluted $ (0.20 ) $ (0.08 ) $ (0.08 ) $ (0.06 )

Description of Business and S35

Description of Business and Significant Accounting Policies - Customer Concentration Risk (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Customer Concentration Risk | Revenue | CenturyLink
Concentration Risk [Line Items]
Concentration of credit risk, percentage	22.00%	23.00%	26.00%

Description of Business and S36

Description of Business and Significant Accounting Policies - Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2015
Computer Equipment
Property, Plant and Equipment [Line Items]
Useful life of property and equipment	2 years
Purchased Software
Property, Plant and Equipment [Line Items]
Useful life of property and equipment	3 years
Test Equipment
Property, Plant and Equipment [Line Items]
Useful life of property and equipment	3 years
Furniture and Fixtures
Property, Plant and Equipment [Line Items]
Useful life of property and equipment	7 years

Description of Business and S37

Description of Business and Significant Accounting Policies - Textual (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Certain Terms [Line Items]
Product warranty period	3 years
Cash held by foreign subsidiaries	$ 5,400,000
Restricted cash	0	$ 295,000
Accumulated impairment loss of goodwill	0
Company's fair value in excess of carrying amount	$ 155,000,000
Company's fair value in excess of carrying amount, percent	59.00%
Company's fair value in excess of carrying amount, using market capitalization	$ 153,800,000
Company's fair value in excess of carrying amount, using market capitalization, percent	65.00%
Goodwill, impairment loss		0	$ 0
Impairment of intangible and long-lived assets	$ 0	$ 0	$ 0
Minimum
Schedule of Certain Terms [Line Items]
Customer payment term	30 days
Product warranty period	1 year
Maximum
Schedule of Certain Terms [Line Items]
Customer payment term	120 days
Product warranty period	5 years

Cash, Cash Equivalents and Ma38

Cash, Cash Equivalents and Marketable Securities (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 23,626,000	$ 48,829,000	$ 82,747,000	$ 46,995,000
Marketable securities	49,964,000	62,850,000
Total cash, cash equivalents and marketable securities	73,590,000	111,679,000
Available-for-sale securities in a continuous unrealized loss position in excess of twelve months	0	0
Corporate debt securities
Cash and Cash Equivalents [Line Items]
Marketable securities	35,799,000	61,050,000
U.S. government agency securities
Cash and Cash Equivalents [Line Items]
Marketable securities	10,520,000	0
Commercial paper
Cash and Cash Equivalents [Line Items]
Marketable securities	3,645,000	1,800,000
Cash
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	13,378,000	17,866,000
Money market funds
Cash and Cash Equivalents [Line Items]
Cash and cash equivalents	$ 10,248,000	$ 30,963,000

Cash, Cash Equivalents and Ma39

Cash, Cash Equivalents and Marketable Securities - Amortized Cost and Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 50,058	$ 62,908
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(96)	(59)
Fair Value	49,964	62,850
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,869	61,108
Gross Unrealized Gains	2	1
Gross Unrealized Losses	(72)	(59)
Fair Value	35,799	61,050
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,544
Gross Unrealized Gains	0
Gross Unrealized Losses	(24)
Fair Value	10,520	0
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,645	1,800
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 3,645	$ 1,800

Cash, Cash Equivalents and Ma40

Cash, Cash Equivalents and Marketable Securities - Contractual Maturity (Details) $ in Thousands	Dec. 31, 2015USD ($)
Cash and Cash Equivalents [Abstract]
Marketable securities due in 1 year or less, amortized cost	$ 38,714
Marketable securities due in 1-2 years, amortized cost	11,344
Marketable securities, amortized cost	50,058
Marketable securities due in 1 year or less, fair value	38,651
Marketable securities due in 1-2 years, fair value	11,313
Marketable securities, fair value	$ 49,964

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of fair values of financial assets
Marketable securities	$ 49,964	$ 62,850
Corporate debt securities
Summary of fair values of financial assets
Marketable securities	35,799	61,050
U.S. government agency securities
Summary of fair values of financial assets
Marketable securities	10,520	0
Commercial paper
Summary of fair values of financial assets
Marketable securities	3,645	1,800
Fair Value, Measurements, Recurring
Summary of fair values of financial assets
Total	60,212	93,813
Fair Value, Measurements, Recurring | Corporate debt securities
Summary of fair values of financial assets
Marketable securities	35,799	61,050
Fair Value, Measurements, Recurring | U.S. government agency securities
Summary of fair values of financial assets
Marketable securities	10,520
Fair Value, Measurements, Recurring | Commercial paper
Summary of fair values of financial assets
Marketable securities	3,645	1,800
Fair Value, Measurements, Recurring | Level 1
Summary of fair values of financial assets
Total	10,248	30,963
Fair Value, Measurements, Recurring | Level 1 | Corporate debt securities
Summary of fair values of financial assets
Marketable securities	0	0
Fair Value, Measurements, Recurring | Level 1 | U.S. government agency securities
Summary of fair values of financial assets
Marketable securities	0
Fair Value, Measurements, Recurring | Level 1 | Commercial paper
Summary of fair values of financial assets
Marketable securities	0	0
Fair Value, Measurements, Recurring | Level 2
Summary of fair values of financial assets
Total	49,964	62,850
Fair Value, Measurements, Recurring | Level 2 | Corporate debt securities
Summary of fair values of financial assets
Marketable securities	35,799	61,050
Fair Value, Measurements, Recurring | Level 2 | U.S. government agency securities
Summary of fair values of financial assets
Marketable securities	10,520
Fair Value, Measurements, Recurring | Level 2 | Commercial paper
Summary of fair values of financial assets
Marketable securities	3,645	1,800
Fair Value, Measurements, Recurring | Money market funds
Summary of fair values of financial assets
Money market funds	10,248	30,963
Fair Value, Measurements, Recurring | Money market funds | Level 1
Summary of fair values of financial assets
Money market funds	10,248	30,963
Fair Value, Measurements, Recurring | Money market funds | Level 2
Summary of fair values of financial assets
Money market funds	$ 0	$ 0

Goodwill and Intangible Asset42

Goodwill and Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of intangible assets
Gross Carrying Amount	$ 123,704	$ 123,704
Accumulated Amortization	(117,086)	(98,525)
Net, amortizable intangible assets	6,618	25,179
Core developed technology
Summary of intangible assets
Gross Carrying Amount	68,964	68,964
Accumulated Amortization	(64,047)	(55,694)
Net, amortizable intangible assets	4,917	13,270
Customer relationships
Summary of intangible assets
Gross Carrying Amount	54,740	54,740
Accumulated Amortization	(53,039)	(42,831)
Net, amortizable intangible assets	$ 1,701	$ 11,909

Goodwill and Intangible Asset43

Goodwill and Intangible Assets - Expected Future Amortization (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of expected future amortization
2,016	$ 5,805
2,017	813
Net, amortizable intangible assets	$ 6,618	$ 25,179

Goodwill and Intangible Asset44

Goodwill and Intangible Assets - Textual (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 18,561	$ 18,561	$ 18,561

Balance Sheet Details - Account

Balance Sheet Details - Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of accounts receivable, net
Accounts receivable	$ 48,319	$ 31,493
Allowance for doubtful accounts	(501)	(241)
Product return reserve	(663)	(508)
Accounts receivable, net	$ 47,155	$ 30,744

Balance Sheet Details - Allowan

Balance Sheet Details - Allowance and Product Return Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	$ 241	$ 358	$ 421
Additions Charged to Cost or Expense or Revenue	405	154	(13)
Deductions and Write Offs	(145)	(271)	(50)
Balance At End of Year	501	241	358
Product return reserve
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	508	764	1,740
Additions Charged to Cost or Expense or Revenue	4,224	4,805	3,535
Deductions and Write Offs	(4,069)	(5,061)	(4,511)
Balance At End of Year	$ 663	$ 508	$ 764

Balance Sheet Details - Invento

Balance Sheet Details - Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of inventory, net
Raw materials	$ 2,209	$ 3,180
Finished goods	45,458	43,573
Total inventory	$ 47,667	$ 46,753

Balance Sheet Details - Propert

Balance Sheet Details - Property and Equipment, net (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 75,158	$ 79,523
Accumulated depreciation and amortization	(58,009)	(59,379)
Property and equipment, net	17,149	20,144	$ 17,473
Test equipment
Property, Plant and Equipment [Line Items]
Property and equipment, gross	39,035	40,766
Computer equipment and purchased software
Property, Plant and Equipment [Line Items]
Property and equipment, gross	27,736	30,355
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, gross	1,833	1,852
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 6,554	$ 6,550

Balance Sheet Details - Accrued

Balance Sheet Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Summary of accrued liabilities
Accrued compensation and related benefits	$ 13,809	$ 15,782
Accrued warranty	9,564	9,553
Accrued professional and consulting fees	2,813	5,860
Advance customer payments	1,094	364
Accrued excess and obsolete inventory at contract manufacturers	1,011	888
Accrued non income related taxes	905	581
Advance customer payments	784	851
Accrued non income related taxes	580	1,414
Accrued freight	486	303
Accrued hosting services	466	235
Accrued hosting services	381	412
Income taxes payable	322	269
Accrued other	3,297	2,931
Total accrued liabilities	$ 35,512	$ 39,443

Balance Sheet Details - Deferre

Balance Sheet Details - Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	$ 12,124	$ 12,722
Deferred revenue, non-current	19,569	19,393
Deferred revenue	31,693	32,115
Product and Services
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	8,937	9,753
Deferred revenue, non-current	58	182
Extended Warranty
Deferred Revenue Arrangement [Line Items]
Deferred revenue, current	3,187	2,969
Deferred revenue, non-current	$ 19,511	$ 19,211

Balance Sheet Details - Textual

Balance Sheet Details - Textual (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 10,262	$ 9,263	$ 10,181

Commitments and Contingencies -

Commitments and Contingencies - Future Minimum Payments Under Operating Leases (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 2,666
2,017	2,594
2,018	2,325
2,019	579
2,020	222
Thereafter	248
Total	$ 8,634

Commitments and Contingencies53

Commitments and Contingencies - Product Warranty Activities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Product warranty activities [Roll Forward]
Balance at beginning of period	$ 9,553	$ 10,856	$ 11,762
Warranty charged to cost of revenue	4,661	3,394	4,350
Utilization of warranty	(4,115)	(3,328)	(4,786)
Adjustments to pre-existing warranty	(535)	(1,369)	(470)
Balance at end of period	$ 9,564	$ 9,553	$ 10,856

Commitments and Contingencies54

Commitments and Contingencies - Textual (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Feb. 22, 2011
Lease Commitments
Unamortized Lease Incentive	$ 300
Rent Expense	3,500	$ 4,100	$ 3,900
Purchase Commitments
Accrued excess and obsolete inventory at contract manufacturers	1,011	$ 888
Non-cancelable outstanding purchase orders	$ 7,300
Accrued Warranty
Product warranty period	3 years
Litigation
Trading profits	$ 500
Minimum
Accrued Warranty
Product warranty period	1 year
Maximum
Accrued Warranty
Product warranty period	5 years
Accrued Liabilities
Lease Commitments
Unamortized Lease Incentive	$ 100
Other Long-term Liabilities
Lease Commitments
Unamortized Lease Incentive	200
Petaluma Lease
Lease Commitments
Lease Incentive Received	1,200
Amendment to Petaluma Lease
Lease Commitments
Lease Incentive Received	$ 400
Occam Acquisition | Occam shareholders vs Occam and Occam Board Of Directors
Litigation
Common stock, shares outstanding				15,147,085
Occam Acquisition | Occam shareholders vs Occam and Occam Board Of Directors | Minimum
Litigation
Fair value of Occam's common stock on the Effective Date				$ 7.77
Occam Acquisition | Occam shareholders vs Occam and Occam Board Of Directors | Maximum
Litigation
Fair value of Occam's common stock on the Effective Date				$ 9.65

Net Loss per Share - Basic and

Net Loss per Share - Basic and Diluted Shares Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator:
Net loss	$ (9,546)	$ 922	$ (5,779)	$ (11,930)	$ (2,988)	$ (3,848)	$ (3,951)	$ (10,027)	$ (26,333)	$ (20,814)	$ (17,265)
Denominator:
Weighted-average common shares outstanding									51,489	50,808	49,419
Basic and diluted net loss per common share (in dollars per share)									$ (0.51)	$ (0.41)	$ (0.35)
Potentially dilutive shares, weighted-average									6,120	5,020	5,308

Stockholders' Equity - Stock Op

Stockholders' Equity - Stock Options Activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Stock Options, Number of Shares:
Stock options outstanding, beginning	3,701	2,560
Stock options granted	200
Stock options exercised	(97)
Stock options forfeited	(1,043)
Stock options expired	(106)
Stock options outstanding, ending	2,655	3,701
Stock options vested and expected to vest	2,594
Stock options exercisable	1,822
Stock Options, Weighted-Average Exercise Price Per Share:
Stock options outstanding, beginning (in dollars per share)	$ 11.38
Stock options granted (in dollars per share)	8.91
Stock options exercised (in dollars per share)	6.56
Stock options forfeited (in dollars per share)	10.07
Stock options expired (in dollars per share)	13.29
Stock options outstanding, ending (in dollars per share)	11.81	$ 11.38
Stock options vested and expected to vest (in dollars per share)	11.89
Stock options exercisable (in dollars per share)	$ 13.32
Weighted-average remaining contractual term, stock options outstanding	6 years 8 months 6 days
Weighted-average remaining contractual term, stock options vested and expected to vest	6 years 7 months 21 days
Weighted-average remaining contractual term, stock options exercisable	5 years 11 months 6 days
Aggregate intrinsic value, stock options outstanding	$ 250
Aggregate intrinsic value, stock options vested and expected to vest	250
Aggregate intrinsic value, stock options exercisable	$ 240

Stockholders' Equity - RSU, PRS

Stockholders' Equity - RSU, PRSU and RSA Activities (Details) - $ / shares	1 Months Ended	12 Months Ended
	Jul. 31, 2011	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
RSUs
RSU, PRSU and RSA, Number of Shares:
Outstanding, beginning		1,734,000	1,506,000
Granted		1,608,000
Vested		(706,000)
Canceled		(167,000)
Outstanding, ending		2,469,000	1,734,000	1,506,000
RSU, PRSU and RSA, Weighted-Average Grant Date Fair Value Per Value:
Outstanding, beginning (in dollars per share)		$ 9.53
Granted (in dollars per share)		8.59	$ 8.72	$ 9.20
Vested (in dollars per share)		10.56
Canceled (in dollars per share)		9.23
Outstanding, ending (in dollars per share)		$ 8.64	$ 9.53
PRSUs
RSU, PRSU and RSA, Number of Shares:
Outstanding, beginning		362,000	413,000
Granted		0
Vested		(148,000)
Canceled		(30,000)
Outstanding, ending		184,000	362,000	413,000
RSU, PRSU and RSA, Weighted-Average Grant Date Fair Value Per Value:
Outstanding, beginning (in dollars per share)		$ 10.53
Granted (in dollars per share)		0	$ 9.16	$ 11.24
Vested (in dollars per share)		11.60
Canceled (in dollars per share)		13.33
Outstanding, ending (in dollars per share)		$ 9.21	$ 10.53
RSAs
RSU, PRSU and RSA, Number of Shares:
Outstanding, beginning		62,000
Granted	423,000	0
Vested		(62,000)
Canceled		0
Outstanding, ending		0	62,000
RSU, PRSU and RSA, Weighted-Average Grant Date Fair Value Per Value:
Outstanding, beginning (in dollars per share)		$ 21.67
Granted (in dollars per share)		0
Vested (in dollars per share)		21.67
Canceled (in dollars per share)		0
Outstanding, ending (in dollars per share)		$ 0	$ 21.67

Stockholders' Equity - Fair Val

Stockholders' Equity - Fair Value of Awards Granted (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per share, stock options	$ 4.56	$ 4.79	$ 4.89
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per share	8.59	8.72	9.20
PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per share	0	9.16	11.24
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value per share	$ 2.03	$ 2.46	$ 2.94

Stockholders' Equity - Assumpti

Stockholders' Equity - Assumptions (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock Options
Weighted average assumptions used to estimate fair value of stock options
Expected volatility	52.00%	52.00%	62.00%
Expected life	6 years 3 months	6 years 2 months 16 days	6 years 18 days
Expected dividend yield	0.00%	0.00%	0.00%
Risk free interest rate	1.56%	1.87%	1.14%
ESPP
Weighted average assumptions used to estimate fair value of stock options
Expected volatility	46.00%	45.00%	50.00%
Expected life	5 months 15 days	6 months	6 months
Expected dividend yield	0.00%	0.00%	0.00%
Risk free interest rate	0.18%	0.07%	0.09%

Stockholders' Equity - Unrecogn

Stockholders' Equity - Unrecognized Stock-based Compensation Expenses (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 3,267
Weighted-average amortization period	2 years 3 months 18 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 14,048
Weighted-average amortization period	2 years 7 months 6 days
PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 116
Weighted-average amortization period	1 year
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 0
Weighted-average amortization period	0 years
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 624
Weighted-average amortization period	4 months

Stockholders' Equity - Warrants

Stockholders' Equity - Warrants Outstanding (Details) - Expiration Date of September 4, 2017 shares in Thousands	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Class of Warrant or Right [Line Items]
Expiration date, warrants	Sep. 4, 2017
Exercise price per share, warrants | $ / shares	$ 19.56
Number of warrants outstanding | shares	15

Stockholders' Equity - Shares R

Stockholders' Equity - Shares Reserved For Future Issuance (Details) - shares	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 02, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding	2,655,000	3,701,000	2,560,000
Shares available for future issuance under ESPP	9,201,000	9,986,000	10,728,000
Common stock warrants	15,000	15,000	23,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding awards, instruments other than options	2,469,000	1,734,000	1,506,000
PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding awards, instruments other than options	184,000	362,000	413,000
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future issuance under ESPP	1,129,000	1,891,000	2,574,000
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future grant under 2010 Plan	2,749,000	2,283,000	3,652,000
Shares available for future issuance under ESPP				4,666,666

Stockholders' Equity - Textual

Stockholders' Equity - Textual (Details)	Feb. 22, 2011USD ($)shares	Apr. 08, 2010	Mar. 26, 2010USD ($)$ / sharesshares	Mar. 21, 2010	Jul. 31, 2011shares	Dec. 31, 2015USD ($)$ / sharesshares	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)shares	Dec. 31, 2013shares	Mar. 02, 2010shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized						100,000,000	100,000,000
Preferred stock, shares authorized						5,000,000	5,000,000
Stock split, conversion ratio				1.5
Initial public offering, price per share (in dollars per share) | $ / shares			$ 13
Underwriter's fee | $			$ 3,800,000
Stock issued in connection with business acquisition, shares	6,400,000
Stock issued in connection with business acquisition, value | $	$ 117,200,000
Dividends declared or paid | $ / shares						$ 0
Preferred stock, shares issued						0	0
Total intrinsic value for exercised stock options | $						$ 300,000	$ 600,000	$ 1,000,000
Exercise of stock options and warrants | $						638,000	1,668,000	747,000
Total fair value of stock options vested | $						3,000,000	$ 3,700,000	$ 3,900,000
Fair value of accelerated stock awards | $						$ 600,000
Shares issued in connection with Employee Stock Purchase Plan						761,844
Shares available for future issuance under ESPP						9,201,000	9,986,000	10,728,000	10,728,000
Stock based compensation | $						$ 13,805,000	$ 16,017,000	$ 19,921,000
Percent of historical volatility						50.00%
Percent of implied volatility						50.00%
Stock options granted, shares						200,000
Aggregate fair value of options and RSUs | $						$ 13,805,000	$ 16,017,000	$ 19,921,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility						52.00%	52.00%	62.00%
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conversion basis description						Each RSU granted under the 2010 Plan represents a right to receive one share of the Company’s common stock (subject to adjustment for certain specified changes in the capital structure of the Company) upon the completion of a specific period of continued service.
Awards granted, shares						1,608,000
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting rights					vest 25% per year for 4 years from the grant date
Awards granted, shares					423,000	0
PRSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, shares						0
PRSUs | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period, PRSU						2 years
Target performance rate, PRSU							0.00%
PRSUs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance period, PRSU						3 years
Target performance rate, PRSU							200.00%
Prior Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						4 years
Contractual term, stock options							10 years
2010 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum exercise price of stock option, percentage						100.00%
Vesting period						4 years
Contractual term, stock options						10 years
Automatic annual increase of reserved shares									3,333,330
Vesting rights						vest 25% on the first anniversary of the vesting commencement date and on a monthly basis thereafter for a period of an additional three years
Shares available for future issuance under ESPP										4,666,666
2010 Plan | Incentive Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum shares allowed to be issued						17,150,494
2010 Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						4 years
RSU granted converted into common stock						1
Award vesting rights, percentage						25.00%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
ESPP, maximum employee payroll deduction percentage						15.00%
Maximum number of shares employee can purchase during offering period						2,000
ESPP, discounted purchase price percentage						85.00%
Offering period						6 months
Shares authorized						4,300,000
Shares available for future issuance under ESPP						1,129,000
Transition and Separation Agreement with Roger Weingarth
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value recognized for accelerated stock awards | $						$ 0	$ 100,000	$ 500,000
Incentive Stock Option | Prior Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum exercise price of stock option, percentage						100.00%
Non-qualified Stock Option | 2002 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum exercise price of stock option, percentage						100.00%
Underwriter Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, issuance date		Apr. 8, 2010
Common stock, sold in initial public offering, shares			949,339
Proceeds from issuance of common stock | $			$ 12,300,000
Stock issuance costs | $			$ 800,000
IPO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, issuance date			Mar. 26, 2010
Common stock, sold in initial public offering, shares			4,166,666
Proceeds from issuance of common stock | $			$ 54,200,000
Stock issuance costs | $			$ 4,600,000
Occam Acquisition
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted, shares	536,190
Aggregate fair value of options and RSUs | $	$ 5,800,000
Value of options in consideration for business combination | $	1,400,000
Value of certain options and RSUs allocated to post-combination expense | $	$ 4,500,000
Occam Acquisition | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awards granted, shares	42,654
Year one vesting | 2010 Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting rights, percentage						25.00%
Additional years of monthly vesting | 2010 Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period						3 years

Stockholders' Equity Stockholde

Stockholders' Equity Stockholders' Equity - Stock Repurchase (Details) - Common Stock - USD ($)	12 Months Ended
	Dec. 31, 2015	Apr. 26, 2015
Class of Stock [Line Items]
Stock repurchase program, authorized amount		$ 40,000,000
Number of shares repurchased	3,540,530
Shares repurchased, value	$ 27,200,000
Average price per share	$ 7.68
Remaining authorized repurchase amount	$ 12,800,000

Employee Benefit Plan - Textual

Employee Benefit Plan - Textual (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Company matching contributions, 401(K) Plan	$ 1.8	$ 1.5	$ 1.5

Accumulated Other Comprehensi66

Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	$ 80	$ 190	$ 132
Other comprehensive loss before reclassification adjustments	(275)	(109)
Reclassification adjustment for realized gains on marketable securities included in net loss		(1)
Total other comprehensive income (loss), net of tax	(275)	(110)	58
Balance at end of period	(195)	80	190
Unrealized Gains and Losses on Available-for-Sale Marketable Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	(58)	0	0
Other comprehensive loss before reclassification adjustments	(36)	(57)
Reclassification adjustment for realized gains on marketable securities included in net loss		(1)
Total other comprehensive income (loss), net of tax		(58)	0
Balance at end of period	(94)	(58)	0
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning of period	138	190	132
Other comprehensive loss before reclassification adjustments	(239)	(52)
Reclassification adjustment for realized gains on marketable securities included in net loss		0
Total other comprehensive income (loss), net of tax		(52)	58
Balance at end of period	$ (101)	$ 138	$ 190

Credit Facility - Textual (Deta

Credit Facility - Textual (Details)	Jul. 29, 2013USD ($)extention	Mar. 28, 2015USD ($)	Dec. 31, 2015USD ($)payment	Dec. 31, 2014USD ($)	Dec. 31, 2013USD ($)	Jun. 28, 2013USD ($)
Line of Credit Facility [Line Items]
Term loan repayment, frequency of equal quarterly payments | payment			20
Revolving credit facility, maximum capacity	$ 50,000,000
Revolving credit facility, maturity date	Jul. 29, 2016
Increase (decrease) in restricted cash		$ (300,000)	$ (295,000)	$ 0	$ 295,000
Number of one-year period extensions | extention	2
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.
Commitment fee percentage			0.25%
Outstanding letters of credit			$ 0
Payments of debt issuance costs			138,000	$ 0	$ 316,000
Unamortized debt issuance expense			200,000
Borrowings under the credit facility			0
Prepaid Expenses and Other Current Assets
Line of Credit Facility [Line Items]
Unamortized debt issuance expense			100,000
Other Assets
Line of Credit Facility [Line Items]
Unamortized debt issuance expense			$ 100,000
Swingline Facility
Line of Credit Facility [Line Items]
Revolving credit facility, maximum capacity	$ 10,000,000
Swingline loan repayment period			10 days
Prior Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, maximum capacity						$ 30,000,000
Revolving credit facility, maturity date			Jun. 30, 2013
Letter of Credit
Line of Credit Facility [Line Items]
Revolving credit facility, maximum capacity	20,000,000
Long-term Debt
Line of Credit Facility [Line Items]
Revolving credit facility, maximum capacity	$ 25,000,000
Base Rate | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	0.75%
Base Rate | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.25%
LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.00%
LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.50%

Income Taxes - Loss before Prov

Income Taxes - Loss before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic	$ (27,674)	$ (21,495)	$ (18,500)
Foreign	1,876	1,262	1,221
Loss before provision for (benefit from) income taxes	$ (25,798)	$ (20,233)	$ (17,279)

Income Taxes - Components of In

Income Taxes - Components of Income Tax Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal	$ 0	$ 0	$ (274)
State	90	104	41
Foreign	493	469	315
Current income tax	583	573	82
Foreign	(48)	8	(96)
Deferred income tax	(48)	8	(96)
Provision for (benefit from) income taxes	$ 535	$ 581	$ (14)

Income Taxes - Income Tax Rate

Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory rate	34.00%	34.00%	34.00%
State statutory rate	2.60%	2.50%	3.40%
Foreign operations	1.10%	(0.10%)	1.40%
Release of FIN 48 liability and interest	0.00%	0.00%	0.70%
R&D tax credits	11.20%	9.20%	13.10%
Foreign income inclusion	(2.40%)	(0.30%)	0.00%
Non-deductible stock compensation	(1.90%)	(0.90%)	(7.30%)
Other permanent items	(2.00%)	(1.50%)	2.80%
Tax true-up	(1.30%)	(0.20%)	1.00%
Valuation allowance	(43.40%)	(45.60%)	(49.00%)
Effective tax rate	(2.10%)	(2.90%)	0.10%

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Gross [Abstract]
Net operating loss carryforwards	$ 167,387	$ 166,150
Tax credit carryforwards	27,654	25,052
Depreciation and amortization	1,947	1,275
Accruals and reserves	12,427	13,810
Deferred revenue	9,822	9,930
Stock-based compensation	5,198	5,138
Other	528	498
Gross deferred tax assets	224,963	221,853
Valuation allowance	(222,410)	(212,703)
Net deferred tax assets	2,553	9,150
Deferred Tax Liabilities, Gross [Abstract]
Gross deferred tax liabilities	(2,229)	(8,995)
Other	(130)	0
Gross deferred tax liabilities	(2,359)	(8,995)
Net deferred tax assets reflected in balance sheet	194	155
Deferred Tax Assets, Net [Abstract]
Deferred tax assets, current	0	785
Deferred tax assets, long-term	194	155
Deferred tax liabilities, long-term	0	(785)
Net deferred tax assets reflected in balance sheet	$ 194	$ 155

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits Activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Unrecognized Tax Benefits [Roll Forward]
Balance at beginning of period	$ 15,421	$ 14,382
Additions for tax positions related to prior year	56	76
Reductions for tax positions related to prior year	(59)	0
Additions for tax positions related to current year	1,179	963
Balance at end of period	$ 16,597	$ 15,421

Income Taxes - Textual (Details

Income Taxes - Textual (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Net deferred tax assets	$ 194,000	$ 155,000
Provision for (benefit from) income taxes	535,000	581,000	$ (14,000)
Increase (decrease) In valuation allowance	9,700,000	5,400,000
Excess tax benefits of stock option deductions included in valuation allowance	100,000	100,000
Research and development credits	27,654,000	25,052,000
Undistributed earnings of foreign subsidiaries	2,300,000
Unrecognized tax benefits	16,597,000	15,421,000	$ 14,382,000
Accrued interest or penalties for uncertain income tax	0
US Federal
Income Taxes [Line Items]
Operating loss carryforward	552,700,000
Deduction related to excess tax benefits from stock options which are not included in net operating loss carryforward	37,800,000	37,600,000
Research and development credits	22,000,000
State
Income Taxes [Line Items]
Operating loss carryforward	122,100,000
Deduction related to excess tax benefits from stock options which are not included in net operating loss carryforward	34,200,000	$ 34,000,000
California State
Income Taxes [Line Items]
Research and development credits	25,300,000
Other State
Income Taxes [Line Items]
Research and development credits	$ 2,200,000

Segment Information - Revenue b

Segment Information - Revenue by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 104,999	$ 112,297	$ 99,129	$ 91,038	$ 111,633	$ 105,769	$ 98,005	$ 85,820	$ 407,463	$ 401,227	$ 382,618
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									360,077	352,458	333,403
Caribbean
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									13,358	18,725	17,466
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									11,090	5,948	17,397
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									10,198	9,995	10,231
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue									$ 12,740	$ 14,101	$ 4,121

Segment Information - Property

Segment Information - Property and Equipment by Geographic Region (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 17,149	$ 20,144	$ 17,473
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	15,362	17,852	14,969
China
Revenues from External Customers and Long-Lived Assets [Line Items]
Property and equipment, net	$ 1,787	$ 2,292	$ 2,504

Quarterly Financial Data - Un76

Quarterly Financial Data - Unaudited (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 26, 2015	Jun. 27, 2015	Mar. 28, 2015	Dec. 31, 2014	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 104,999	$ 112,297	$ 99,129	$ 91,038	$ 111,633	$ 105,769	$ 98,005	$ 85,820	$ 407,463	$ 401,227	$ 382,618
Gross profit	46,537	53,113	48,289	42,490	51,441	45,080	44,342	36,926	190,429	177,789	171,074
Operating income (loss)	(9,735)	877	(5,765)	(11,887)	(2,853)	(3,744)	(3,890)	(9,897)	(26,510)	(20,384)	(18,453)
Net income (loss)	$ (9,546)	$ 922	$ (5,779)	$ (11,930)	$ (2,988)	$ (3,848)	$ (3,951)	$ (10,027)	$ (26,333)	$ (20,814)	$ (17,265)
Net income (loss) per common share, basic (in dollars per share)	$ (0.19)	$ 0.02	$ (0.11)	$ (0.23)	$ (0.06)	$ (0.08)	$ (0.08)	$ (0.20)
Net income (loss) per common share, diluted (in dollars per share)	$ (0.19)	$ 0.02	$ (0.11)	$ (0.23)	$ (0.06)	$ (0.08)	$ (0.08)	$ (0.20)

Schedule II. Valuation and Qu77

Schedule II. Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	$ 241	$ 358	$ 421
Additions Charged to Cost or Expense or Revenue	405	154	(13)
Deductions and Write Offs	(145)	(271)	(50)
Balance At End of Year	501	241	358
Product return reserve
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance At Beginning of Year	508	764	1,740
Additions Charged to Cost or Expense or Revenue	4,224	4,805	3,535
Deductions and Write Offs	(4,069)	(5,061)	(4,511)
Balance At End of Year	$ 663	$ 508	$ 764