A10 Networks (ATEN) 10-K 1 Mar 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. 19, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	ATEN
Entity Registrant Name	A10 Networks, Inc.
Entity Central Index Key	1,580,808
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		64,307,946
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 269.4

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
CURRENT ASSETS
Cash and cash equivalents	$ 98,117	$ 91,905
Accounts receivable, net of allowances of $4,067 and $3,246 as of December 31, 2015 and December 31, 2014	57,778	54,003
Inventory	18,291	20,701
Prepaid expenses and other current assets	5,064	4,732
Total current assets	179,250	171,341
Property and equipment, net	8,903	10,780
Other non-current assets	4,398	4,859
Total Assets	192,551	186,980
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable	10,508	8,994
Accrued liabilities	27,757	22,435
Deferred revenue, current	49,572	39,256
Total current liabilities	87,837	70,685
Deferred revenue, non-current	23,232	17,964
Other non-current liabilities	1,414	1,766
Total Liabilities	$ 112,483	$ 90,415
Commitments and contingencies
STOCKHOLDERS’ EQUITY (DEFICIT):
Common stock, par value $0.00001 — 500,000 shares authorized as of December 31, 2015 and December 31, 2014; 64,172 and 61,377 shares issued and outstanding as of December 31, 2015 and December 31, 2014	$ 1	$ 1
Additional paid-in capital	301,886	278,349
Accumulated deficit	(221,819)	(181,785)
Total Stockholders' Equity	80,068	96,565
Total Liabilities And Stockholders' Equity	$ 192,551	$ 186,980

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Allowance for doubtful accounts receivable	$ 4,067	$ 3,246
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	64,172,000	61,377,000
Common stock, shares outstanding	64,172,000	61,377,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Products	$ 138,301	$ 134,486	$ 112,045
Services	60,654	45,021	29,693
Total revenue	198,955	179,507	141,738
Cost of revenue:
Products	33,096	31,084	25,284
Services	15,672	11,853	8,112
Total cost of revenue	48,768	42,937	33,396
Gross profit	150,187	136,570	108,342
Operating expenses:
Sales and marketing	104,531	96,837	70,756
Research and development	54,843	49,903	33,348
General and administrative	27,055	22,938	15,556
Litigation expense (benefit)	2,204	(2,837)	11,525
Total operating expenses	188,633	166,841	131,185
Loss from operations	(38,446)	(30,271)	(22,843)
Other income (expense), net:
Interest expense	(509)	(1,028)	(1,495)
Interest income and other income (expense), net	(332)	(1,914)	(2,118)
Total other expense, net	(841)	(2,942)	(3,613)
Loss before provision for income taxes	(39,287)	(33,213)	(26,456)
Provision for income taxes	747	1,507	640
Net loss	(40,034)	(34,720)	(27,096)
Accretion of redeemable convertible preferred stock dividend	0	(1,150)	(1,982)
Net loss attributable to common stockholders	$ (40,034)	$ (35,870)	$ (29,078)
Net loss per share attributable to common stockholders:
Basic and Diluted (in dollars per share)	$ (0.64)	$ (0.74)	$ (3.14)
Weighted-average shares used in computing net loss per share attributable to common stockholders, basic and diluted:
Weighted-average shares outstanding - basic and diluted	62,428	48,682	9,262

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Preferred StockRedeemable Convertible Preferred Stock	Preferred StockConvertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit
Balance at beginning of period (shares) at Dec. 31, 2012		0	30,122	9,246
Balance at beginning of period at Dec. 31, 2012	$ (111,892)	$ 0	$ 41,737		$ 8,077	$ (119,969)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation expense	4,282				4,282
Issuance of stock (shares)		80
Issuance of stock		$ 79,444
Accretion of Series D redeemable convertible preferred stock dividend	(1,982)	$ 1,982			(1,982)
Issuance of stock due to conversion of preferred stock (shares)			(447)
Issuance of stock due to conversion of preferred stock			$ 3,012
Common issued under employee equity incentive plans, net of unvested portion (shares)				822
Common stock issued under employee equity incentive plans, net of unvested portion	1,174				1,174
Vesting of early exercise stock options, net of repurchases (shares)				(36)
Vesting of early exercise stock options, net of repurchases	634				634
Net loss	(27,096)					(27,096)
Balance at end of period (shares) at Dec. 31, 2013		80	30,569	10,032
Balance at end of period at Dec. 31, 2013	(134,880)	$ 81,426	$ 44,749		12,185	(147,065)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation expense	12,359				12,359
Issuance of stock (shares)				9,000
Issuance of stock	120,286				120,286
Accretion of Series D redeemable convertible preferred stock dividend	(1,150)	$ 1,150			(1,150)
Issuance of stock due to conversion of preferred stock (shares)		(80)	(30,569)	(39,997)
Issuance of stock due to conversion of preferred stock	127,325	$ (82,576)	$ (44,749)	$ 1	127,324
Common issued under employee equity incentive plans, net of unvested portion (shares)				2,352
Common stock issued under employee equity incentive plans, net of unvested portion	6,574				6,574
Vesting of early exercise stock options, net of repurchases (shares)				(4)
Vesting of early exercise stock options, net of repurchases	771				771
Net loss	(34,720)					(34,720)
Balance at end of period (shares) at Dec. 31, 2014		0	0	61,377
Balance at end of period at Dec. 31, 2014	96,565	$ 0	$ 0	$ 1	278,349	(181,785)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock based compensation expense	16,861				16,861
Accretion of Series D redeemable convertible preferred stock dividend	0
Common issued under employee equity incentive plans, net of unvested portion (shares)				2,700
Common stock issued under employee equity incentive plans, net of unvested portion	6,232				6,232
Vesting of early exercise stock options, net of repurchases (shares)				95
Vesting of early exercise stock options, net of repurchases	444				444
Net loss	(40,034)
Balance at end of period (shares) at Dec. 31, 2015		0	0	64,172
Balance at end of period at Dec. 31, 2015	$ 80,068	$ 0	$ 0	$ 1	$ 301,886	$ (221,819)

Consolidated Statement of Stoc6

Consolidated Statement of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2013USD ($)
Preferred Stock | Redeemable Convertible Preferred Stock
Convertible preferred stock issued, issuance costs	$ 556

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net loss	$ (40,034,000)	$ (34,720,000)	$ (27,096,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	8,716,000	10,121,000	7,080,000
Stock-based compensation	16,861,000	12,359,000	4,282,000
Gain on settlement of contractual liability	0	(6,993,000)	0
Provision for doubtful accounts and sales returns	2,531,000	935,000	1,788,000
Other Noncash Income (Expense)	(82,000)	32,000	2,000
Changes in operating assets and liabilities:
Accounts receivable, net	(5,977,000)	(17,281,000)	(15,549,000)
Inventory	(430,000)	(8,914,000)	(8,489,000)
Prepaid expenses and other assets	(405,000)	(3,017,000)	1,588,000
Accounts payable	1,109,000	903,000	2,495,000
Accrued liabilities	5,345,000	6,724,000	2,133,000
Accrued litigation expenses	6,000	(6,066,000)	(6,797,000)
Deferred revenue	15,584,000	15,989,000	13,525,000
Other	167,000	(610,000)	(95,000)
Net cash provided by (used in) operating activities	3,391,000	(30,538,000)	(25,133,000)
Cash flows from investing activities:
Purchases of property and equipment	(3,477,000)	(6,100,000)	(2,993,000)
Net cash used in investing activities	(3,477,000)	(6,100,000)	(2,993,000)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee equity incentive plans, net of repurchases	6,019,000	7,030,000	2,392,000
Proceeds from initial public offering, net of offering costs	0	121,017,000	(656,000)
Proceeds from issuance of Series D redeemable convertible preferred stock, net of issuance costs	0	0	79,444,000
Principal payments on convertible promissory note in relation to settlement of litigation	0	0	(70,000,000)
Proceeds from revolving credit facility	0	0	33,988,000
Principal payments on revolving credit facility	0	(20,000,000)	(20,000,000)
Principal payments on term loan	0	0	(631,000)
Proceeds from exercise of convertible preferred stock warrants	0	0	813,000
Other	279,000	(297,000)	(298,000)
Net cash provided by financing activities	6,298,000	107,750,000	25,052,000
Net increase (decrease) in cash and cash equivalents	6,212,000	71,112,000	(3,074,000)
Cash and cash equivalents—beginning of period	91,905,000	20,793,000	23,867,000
Cash and cash equivalents—end of period	98,117,000	91,905,000	20,793,000
Supplemental Disclosures of Cash Flow Information:
Cash paid for income taxes, net of refunds	980,000	1,108,000	698,000
Cash paid for interest	170,000	503,000	1,208,000
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Inventory transfers to property and equipment	2,840,000	5,379,000	5,638,000
Vesting of early exercised stock options	444,000	771,000	654,000
Purchases of property and equipment included in accounts payable and accrued liabilities	486,000	78,000	167,000
Conversion of preferred stock into common stock	0	127,325,000	0
Accretion of Series D redeemable convertible preferred stock	0	1,150,000	1,982,000
Costs related to the initial public offering included in accounts payable and accrued liabilities	0	75,000	1,776,000
Issuance of convertible promissory note in relation to settlement of litigation	0	0	70,000,000
Reclassification of the convertible preferred stock warrant liability to additional paid-in capital upon the exercise of the convertible preferred stock warrants	$ 0	$ 0	$ 2,199,000

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Description of Business and Basis of Presentation A10 Networks, Inc. (together with our subsidiaries, the “Company”, “we”, “our” or “us”) was incorporated in California in 2004 and reincorporated in Delaware in 2014. We are headquartered in San Jose, California and have wholly-owned subsidiaries throughout the world including Asia and Europe. Our solutions enable enterprises, service providers, Web giants and government organizations to accelerate, secure and optimize the performance of their data center applications and secure their users, applications and infrastructure from internet, web and network threats at scale. During 2015, we offered three software based advanced application networking and network security solutions to address end-customer needs, including Application Delivery Controllers ("ADC") to optimize web and back-office application performance, Carrier Grade Network Address Translation ("CGN") to provide network address and protocol translation services for service provider networks and Threat Protection System ("TPS") for network-wide multi-vector DDoS security protection. Our solutions are cloud-ready and available, in variety of form factors such as optimized hardware appliances, in the cloud as software, and as virtual appliances. Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). The accompanying consolidated financial statements include the accounts of A10 Networks, Inc., and our wholly owned subsidiaries. All inter-company balances and transactions have been eliminated in consolidation. We had no comprehensive income (loss) other than our net income (loss), hence our comprehensive income (loss) is the same as the net income (loss) for all periods presented. Pursuant to the accounting guidance provided by Accounting Standard Codification ("ASC") 220 Comprehensive Income, we did not present statements of comprehensive income (loss) for the periods presented . Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Those estimates and assumptions affect including revenue recognition and deferred revenue, allowance for doubtful accounts, sales return reserve, valuation of inventory, contingencies and litigation, income taxes and determination of fair value of stock-based compensation. These estimates are based available as of the date of the consolidated financial statements; therefore, actual results could differ from management’s estimates. Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in interest income and other income (expense), net in the Consolidated Statements of Operations. We recorded $0.5 million , $2.0 million and $2.1 million foreign exchange loss as part of interest income and other income (expense), net in the Consolidated Statements of Operations during the years ended December 31, 2015, 2014 and 2013. Vendor Business Concentration We rely on third parties to manufacture our hardware appliances and we purchase raw materials from third-party vendors. We outsourced substantially all of our manufacturing services to two independent manufacturers. In addition, we purchase certain strategic component inventory which is consigned to our third-party manufacturers. Other hardware components included in our products are sourced from various suppliers by our manufacturers and are principally industry standard parts and components that are available from multiple vendors. Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents and accounts receivable. Our cash and cash equivalents are invested in high-credit quality financial instruments with banks and financial institutions. We believe that the financial institutions that hold our cash and cash equivalents are financially sound and, accordingly, are subject to minimal credit risk. Our bank deposits may be in excess of insured limits provided on such deposits. Our accounts receivable are unsecured and represent amounts due to us based on contractual obligations of our customers. We mitigate credit risk in respect to accounts receivable by performing periodic credit evaluations of our customers to assess the probability of accounts receivable collection based on a number of factors, including past transaction experience with the customer, evaluation of their credit history, limiting the credit extended and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent more than 10% of our total revenue for each period presented, or our gross accounts receivable balance as of each respective balance sheet date. Revenue from our significant customers as a percentage of our total revenue for the years ended December 31, 2015, 2014 and 2013 are as follows: Years Ended December 31, 2015 2014 2013 Customers Customer A * 13% * Customer B * * 15% Customer C * * 10% * represents less than 10% of total revenue Two of our customers account for 27% (Customer D) and 11% (Customer A) of our gross accounts receivable as of December 31, 2015. No customer accounted for 10% or more of our total gross accounts receivable as of December 31, 2014. Cash and Cash Equivalents We consider all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand and highly liquid investments in money market funds. As of December 31, 2015 and 2014, our total cash and cash equivalents was $98.1 million and $91.9 million , respectively. Fair Value Measurement Assets and liabilities recorded at fair value on a recurring basis in the Consolidated Balance Sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level I —Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level II —Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III —Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. As of December 31, 2015 and 2014, our financial instruments entirely consist of Level I assets. Level I assets include highly liquid money market funds that are included in cash and cash equivalents. Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. We evaluate the collectability of our accounts receivable based on known collection risks and historical experience. In circumstances where we are aware of a specific customer’s inability to meet its financial obligations to us (e.g., bankruptcy filings or substantial downgrading of credit ratings), we record a specific reserve for bad debts against amounts due to reduce the net recognized receivable to the amount we reasonably believe will be collected. For all other customers, we record reserves for bad debts based on the length of time the receivables are past due and our historical experience of collections and write-offs. If circumstances change, such as higher-than-expected defaults or an unexpected material adverse change in a major customer’s ability to meet its financial obligations, our estimate of the recoverability of the amounts due could be reduced by a material amount. Inventory Inventory consists primarily of finished goods and related component parts and is stated at the lower of standard cost, (which approximates actual cost on a first-in, first-out basis), or market value (estimated net realizable value). We evaluate inventory for excess and obsolete products, based on management’s assessment of future demand and market conditions. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. Inventory write downs are included as a component of cost of products revenue in the accompanying Consolidated Statements of Operations. Property and Equipment, Net Property and equipment, including leasehold improvements, are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Depreciation on property and equipment, excluding leasehold improvements, ranges from one to three years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements ranges from two to eight years. Revenue Recognition We derive revenue from two sources: (i) products revenue, which includes hardware and perpetual software license revenue; and (ii) services revenue, which include post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, when all of the following criteria are met: persuasive evidence of an arrangement exists, delivery or performance has occurred, the sales price is fixed or determinable, and collection is reasonably assured. We define each of the four criteria above as follows: • Persuasive evidence of an arrangement exists. Evidence of an arrangement consists of a purchase order issued pursuant to the terms and conditions of a master sales agreement. • Delivery or performance has occurred. We use shipping documents or written evidence of customer acceptance, when applicable, to verify delivery or performance. We recognize product revenue upon transfer of title and risk of loss, which primarily is upon shipment to customers. We do not have significant obligations for future performance, such as customer acceptance provisions, rights of return, or pricing credits, associated with our sales. • The sales price is fixed or determinable. We assess whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. • Collection is reasonably assured. We assess probability of collection on a customer-by-customer basis. Our customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years. Unearned PCS revenue is included in deferred revenue. Professional service revenue primarily consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Multiple-Element Arrangements Our hardware with the embedded software solutions (which is a proprietary operating system that together with the hardware delivers the functionality desired by our customers), is considered a separate unit of accounting from PCS because it has value to the customer on a standalone basis and our sales arrangements do not include a right of return for delivered products. For multiple-element arrangements, we allocate revenue to each unit of accounting based on an estimated selling price at the inception of the arrangement. The total arrangement consideration is allocated to each separate unit of accounting using the relative selling price method. We limit the amount of revenue recognized for delivered elements to an amount that is not contingent upon future delivery of additional products or service. When applying the relative selling price method, we determine the selling price for each element using (i) vendor-specific objective evidence, or VSOE, of selling price, if available; (ii) third-party evidence, or TPE, of selling price, if VSOE is not available; and (iii) best estimate of selling price, or BESP, if neither VSOE nor TPE is available. • VSOE. We determine VSOE based on our historical pricing and discounting practices for the specific products and services when sold separately. In determining VSOE, we require that a substantial majority of the stand-alone selling prices fall within a reasonably narrow pricing range. • TPE. When VSOE cannot be established for deliverables in multiple-element arrangements, we apply judgment with respect to whether we can establish a selling price based on TPE. TPE is determined based on competitor prices for interchangeable products or services when sold separately to similarly situated customers. However, as our products contain a significant element of proprietary technology and our solutions offer substantially different features and functionality, the comparable pricing of products with similar functionality typically cannot be obtained. Additionally, as we are unable to reliably determine what competitors products’ selling prices are on a stand-alone basis, we are not typically able to determine TPE. • BESP. When we are unable to establish selling price using VSOE or TPE, we use BESP in our allocation of arrangement consideration. The objective of BESP is to determine the price at which we would transact a sale if the product or service was sold regularly on a standalone basis. As we have not been able to establish VSOE or TPE for our products and some of our services, we determine BESP for the purposes of allocating the arrangement, primarily based on historical transaction pricing. Historical transactions are segregated based on our pricing model and go-to-market strategy, which include factors such as the geographies in which our products and services were sold (domestic or international), offering type (product series, and level of support for PCS) and type of sales channel. The determination of BESP is made through consultation with and approval by management. We may occasionally accept returns to address customer satisfaction issues or solution-fit issues even though there is no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period gross revenues. Specific customer returns and allowances are considered within this estimate. Management also analyzes changes in customer demand and acceptance of products when evaluating the adequacy of returns and sales allowances. Deferred Revenue Deferred product revenue relates to arrangements where not all revenue recognition criteria have been met. Deferred services revenue primarily represents PCS contracts billed in advance and revenue is recognized ratably over the service contract term, typically one to five years. The current portion of deferred revenue represents the amounts that are expected to be recognized as revenue within one year of the Consolidated Balance Sheets date. Shipping and Handling Shipping charges billed to customers are included in revenue and the related shipping costs are included in cost of revenue in the accompanying consolidated statements of operations. Research and Development Costs Research and development efforts are focused on new product development and on developing additional functionality for our existing products. These expenses consist of personnel costs, and to a lesser extent, prototype materials, depreciation and certain allocated facilities and information technology infrastructure costs. We expense research and development costs as incurred. Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by our chief operating decision maker in deciding how to allocate resources and assessing performance. Our chief operating decision maker is our Chief Executive Officer. Our Chief Executive Officer who reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. Accordingly, we have a single reportable segment and operating segment structure. Stock-Based Compensation We recognize stock-based compensation cost for only those shares ultimately expected to vest on a straight-line basis over the requisite service period of the award. We recognize compensation expense for all stock-based payment awards granted to employees, including stock options, restricted stock units (“RSUs”) and purchases under our 2014 Employee Stock Purchase Plan (“2014 Purchase Plan”), based on the estimated fair value on the date of the grant. The fair value of each stock option granted is estimated using the Black-Scholes option pricing model. The fair value of each RSU granted represents the closing price of our common stock on the date of grant. The fair value of purchases under our 2014 Purchase Plan is calculated based on the closing price of our common stock on the date of grant and the value of put and call options estimated using the Black-Scholes option pricing model. Stock-based compensation is recognized on a straight-line basis over the requisite service period, net of estimated forfeitures. We estimate the fair value of market-performance based restricted stock units ("MSUs") using a Monte Carlo simulation model which requires the input of assumptions, including expected term, stock price volatility and the risk-free rate of return. In addition, judgment is also required in estimating the number of stock-based awards that are expected to be forfeited. Forfeitures are estimated based on historical experience at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The assumptions used in calculating the fair value of share-based payment awards represent management’s best estimates, but these estimates involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and we use different assumptions, our stock-based compensation expense could be materially different in the future. Warranty Costs Our appliance hardware and software generally carry a warranty period of 90 days. Estimates of future warranty costs are based on actual historical returns experience and the application of those historical return rates to our in-warranty installed base. Warranty costs to repair or replace items sold to customers have been insignificant for the years ended December 31, 2015, 2014 and 2013. Litigation and Contingencies Litigation is comprised of legal expenses incurred in defending ourselves against litigation matters and our change in litigation reserve. Legal expenses are recorded in our Consolidated Statements of Operations as incurred when the legal services are provided. Some of these proceedings involve claims that are subject to substantial uncertainties and unascertainable damages. 401(k) Profit Sharing Plan We have a qualified contributory savings plan under Section 401(k) of the Internal Revenue Code that is offered to all of our United States employees. Participants in the plan may elect to contribute up to $18,000 of their annual compensation to the plan for the 2015 calendar year. Individuals who were 50 or older may contribute an additional $6,000 of their annual income. We recorded $0.8 million employer matching contribution during 2015. We did not make matching or discretionary contributions to this plan during 2014 and 2013. Income Taxes We account for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our consolidated financial statements or in our tax returns. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets are expected to be realized or settled. We regularly assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through an adjustment to income tax expense. The factors used to assess the likelihood of realization of our deferred tax assets include our forecast of future taxable income and available tax planning strategies that could be implemented to realize the net deferred tax assets. Assumptions represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. We account for uncertainty in income taxes recognized in our consolidated financial statements by regularly reviewing our tax positions and benefits to be realized. We recognize tax liabilities based upon our estimate of whether, and the extent to which, additional taxes will be due when such estimates are more-likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained upon examination by taxing authorities. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") No. 2014-09, Revenue from Contracts with Customers , which provides new guidance on the recognition of revenue and states that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. The original effective date of this accounting standard was annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date , which deferred the effective date of the new accounting standard. This updated standard is effective for us on January 1, 2018. We are currently evaluating the impact of the adoption of this accounting standard update on our consolidated financial position or results of operations and method of adoption. In April 2015, the FASB issued 2015-03 Interest—Imputation of Interest (Subtopic 835-30) Simplifying the Presentation of Debt Issuance Costs and during August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements , which clarifies the treatment of debt issuance costs from line-of-credit arrangements after adoption of ASU No. 2015-03. This accounting guidance requires debt issuance costs be presented on the balance sheet as a direct reduction from the carrying amount of the related debt liability. ASU No. 2015-15 clarifies that the SEC staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. We adopted ASU No. 2015-15 at the beginning of 2016 and this adoption did not have a material effect on our consolidated financial statements. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory . Under this accounting guidance, inventory will be measured at the lower of cost and net realizable value and other options that currently exist for market value will be eliminated. ASU No. 2015-11 defines net realizable value as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. No other changes were made to the current guidance on inventory measurement. This accounting guidance is effective for us in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of the adoption of this accounting standard update on our consolidated financial statements. In November 2015, the FASB issued an update to ASU No. 2015-17 Income Taxes: Balance Sheet Classification of Deferred Taxes, requiring all deferred tax assets and liabilities, and any related valuation allowance, to be classified as noncurrent on the balance sheet. The classification change for all deferred taxes as noncurrent simplifies entities’ processes as it eliminates the need to separately identify the net current and net noncurrent deferred tax asset or liability in each jurisdiction and allocate valuation allowances. The new accounting guidance is effective for annual reporting periods beginning after December 15, 2016 and interim periods therein. Early adoption is permitted. Additionally, this guidance may be applied either prospectively or retrospectively to all periods presented. We elected to prospectively adopt the accounting standard in the fourth quarter of 2015. Prior periods in our consolidated financial statements were not retrospectively adjusted.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Our financial instruments consist of cash and cash equivalents, accounts receivable, accounts payable and accrued liabilities. Cash equivalents, which include money market funds, are stated at amortized cost, which approximates fair value as of the balance sheet dates, due to the short period of time to maturity. Accounts receivable, accounts payable and accrued expenses are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment. Cash and cash equivalents are carried at fair value. Our money market funds are classified within Level 1 of the fair value hierarchy, as these instruments are valued using quoted market prices. Specifically, we value our investments in money market securities based on quoted market prices in active markets. As of December 31, 2015 and 2014, we had no assets or liabilities classified within Level II or Level III and there were no transfers of instruments between Level I, Level II and Level III regarding fair value measurement. The following table sets forth the fair value of our financial assets measured on a recurring basis by level within the fair value hierarchy (in thousands): December 31, 2015 December 31, 2014 Level 1 Total Level 1 Total Financial Assets Money market funds $ 71,081 $ 71,081 $ 51,047 $ 51,047 We did not have realized gains or losses for the years ended December 31, 2015 and 2014 related to our financial assets.

Balance Sheet and Statement of

Balance Sheet and Statement of Operations Components	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Balance Sheet and Statement of Operations Components	Balance Sheets and Statement of Operations Components Allowance for Doubtful Accounts and Sales Return Reserve For the years ended December 31, 2015, 2014 and 2013, allowance for doubtful accounts and sales return reserve consisted of the following activity (in thousands): December 31, 2015 December 31, 2014 December 31, 2013 Allowance for doubtful accounts, beginning balance $ 1,904 $ 1,836 $ 1,494 Charged to expenses 1,590 76 1,068 Write-offs (607 ) (8 ) (726 ) Allowance for doubtful accounts, ending balance $ 2,887 $ 1,904 $ 1,836 December 31, 2015 December 31, 2014 December 31, 2013 Sales return reserve, beginning balance $ 1,342 $ 902 $ 500 Charged to revenue 940 858 720 Utilization (1,102 ) (418 ) (318 ) Sales return reserve, ending balance $ 1,180 $ 1,342 $ 902 Inventory Components of inventory as of December 31, 2015 and 2014 are shown below (in thousands): December 31, December 31, Raw materials $ 9,418 $ 9,922 Finished goods 8,873 10,779 Total inventory $ 18,291 $ 20,701 Property and Equipment, Net Components of property and equipment, net as of December 31, 2015 and 2014 are shown below (in thousands): Estimated Useful Life (in Years) December 31, December 31, Equipment 1-3 $ 35,836 $ 30,486 Software 1-3 3,548 3,197 Leasehold improvements Lesser of the term of the lease or the estimated useful life 2,492 1,780 Furniture and fixtures 3 864 860 Construction in progress — 83 201 Property and equipment, gross 42,823 36,524 Less: accumulated depreciation and amortization (33,920 ) (25,744 ) Total property and equipment, net $ 8,903 $ 10,780 Depreciation and amortization on our property and equipment for the years ended December 31, 2015, 2014 and 2013 was $8.6 million , $10.0 million and $6.9 million . Deferred Revenue Deferred revenue as of December 31, 2015 and December 31, 2014 consists of the following (in thousands): December 31, December 31, Deferred revenue: Products $ 3,233 $ 2,379 Services 69,571 54,841 Total deferred revenue 72,804 57,220 Less: current portion (49,572 ) (39,256 ) Non-current portion $ 23,232 $ 17,964 Accrued Liabilities Accrued liabilities as of December 31, 2015 and December 31, 2014 consists of the following (in thousands): December 31, December 31, Accrued compensation and benefits $ 18,134 $ 14,447 Accrued tax liabilities 4,520 2,554 Other 5,103 5,434 Total accrued liabilities $ 27,757 $ 22,435 Settlement of Contractual Liability In May 2014, we reached a settlement agreement with one of our legal service providers which resulted in the reduction of a previously accrued contractual liability that totaled $12.0 million . We made a payment of $5.0 million in accordance with the terms of the settlement agreement in June 2014 and recorded a $7.0 million benefit to litigation expense (benefit) at that time.

Credit Facility

Credit Facility	12 Months Ended
	Dec. 31, 2014
Line of Credit Facility [Abstract]
Credit Facility	Credit Facility In September 2013, we entered into a credit agreement with Royal Bank of Canada, JPMorgan Chase Bank, N.A. and Bank of America, N.A. as lenders. The credit agreement provides a three -year $35.0 million revolving credit facility, which includes a maximum $10.0 million letter of credit facility. We had no outstanding borrowings under this credit facility as of December 31, 2015 and 2014. The revolving credit facility expires on September 30, 2016. At our option, the revolving credit facility bears interest at a rate per annum based on either (i) an alternate base rate plus a margin ranging from 1.75% to 2.50% depending on our total leverage ratio, or (ii) the London interbank offered rate, or LIBOR, based on one, two, three or six month interest periods plus a margin ranging from 2.75% to 3.50% depending on our total leverage ratio. The alternate base rate is equal to the greatest of (i) the Royal Bank of Canada’s prime rate, (ii) the federal funds rate plus a margin equal to 0.50% and (iii) the Eurodollar rate for a one month interest period plus a margin equal to 1.00% . Our obligations under the credit agreement are secured by a security interest on substantially all of our assets, including our intellectual property. The credit agreement contains customary non-financial covenants, and also requires us to comply with financial covenants. One financial covenant requires us to maintain a total leverage ratio, which is defined as total consolidated debt to trailing adjusted EBITDA as defined by the credit agreement. In addition, we must maintain a minimum amount of liquidity based on our unrestricted cash and availability under the revolving credit facility. We were in compliance with all financial and nonfinancial covenants under the revolving credit facility as of December 31, 2015 . In addition, we incurred $1.0 million of debt issuance costs that were directly attributable to the issuance of this revolving credit facility which are amortized to interest expense over the three-year term of this credit facility. The unamortized debt issuance costs was $0.3 million and $0.5 million as December 31, 2015 and 2014, and were included within other non current assets in our Consolidated Balance Sheets. We are also required to pay quarterly facility fees of 0.45% per annum on the average daily unused portion of the revolving credit facility.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings From time to time, we may be party or subject to various legal proceedings and claims, either asserted or unasserted, which arise in the ordinary course of business, including proceedings and claims that relate to intellectual property matters. Some of these proceedings involve claims that are subject to substantial uncertainties and unascertainable damages. We account for and disclose possible loss related to these proceedings in accordance with our accounting policy as stated in Note 1. Description of Business and Summary of Significant Accounting Policies in the Notes to Consolidated Financial Statements of this Annual Report on Form 10-K In November 2013, Parallel Networks, LLC (“Parallel Networks”), which we believe is a non-practicing patent holding company, filed a lawsuit against us in the United States District Court for the District of Delaware, alleging that our AX and Thunder series products infringe two of their U.S. patents. In June 2015, we entered into a settlement agreement whereby we obtained a fully-paid up license and the case was dismissed. On January 29, 2015, A10, the members of our Board of Directors, our Chief Financial Officer, and the underwriters of our March 21, 2014, initial public offering ("IPO") were named as defendants in a putative class action lawsuit filed in the Superior Court of the State of California, County of Santa Clara, captioned City of Warren Police and Fire Retirement System v. A10 Networks, Inc., et al., 1-15-CV-276207. Several substantially identical lawsuits were subsequently filed in the same court, bringing the same claims against the same defendants, captioned Arkansas Teacher Retirement System v. A10 Networks, Inc., et al., 1-15-CV-278575 (filed March 25, 2015) and Kaveny v. A10 Networks, Inc., et al. , 1-15-CV-279006 (filed April 6, 2015). On May 29, 2015, the aforementioned putative class actions were consolidated under the caption In re A10 Networks, Inc. Shareholder Litigation, 1-15-CV-276207 (the “Securities Class Action”). On June 30, 2015, plaintiffs filed a Consolidated Class Action Complaint. The Consolidated Complaint seeks unspecified compensatory damages and other relief. On July 31, 2015, the defendants filed demurrers, which the plaintiffs opposed. On November 12, 2015, the Superior Court issued an order overruling the joint demurrer in part. The Superior Court sustained the demurrer, with leave to amend within ten days, with respect to claims against A10 and one of our directors under Section 12 of the Securities Act of 1933. On November 23, 2015, plaintiffs filed their First Amended Consolidated Class Action Complaint, which defendants answered on January 8, 2016. A case management conference is scheduled for May 20, 2016, to address the schedule of upcoming discovery. We intend to vigorously defend this lawsuit. On June 24, 2015, our directors and certain of our officers were named as defendants in a putative derivative lawsuit filed in the Superior Court of the State of California, County of Santa Clara, captioned Hornung v. Chen, et al., 1-15-CV-282286 (the “Derivative Action”). We were also named as a nominal defendant. The complaint seeks to allege breaches of fiduciary duties and other related claims, arising out of allegations that our officers and directors caused us to infringe patents and intellectual property, improperly approved the settlement of prior litigation, failed to adopt and implement effective internal controls, and caused us to issue false and misleading statements in connection with our IPO. Plaintiff seeks unspecified compensatory damages and other equitable relief. On January 29, 2016, defendants filed a joint demurrer to all claims, together with a motion to strike certain allegations. In addition, also on January 29, 2016, we filed a motion to stay the Derivative Action pending the resolution of the related Securities Class Action. We intend to vigorously defend this lawsuit. Lease Obligations and Other Commitments We lease various operating spaces in California, Asia, and Europe under noncancelable operating lease arrangements that expire on various dates through February 2020. These arrangements require us to pay certain operating expenses, such as taxes, repairs, and insurance and contain renewal and escalation clauses. We recognize rent expense under these arrangements on a straight-line basis over the term of the lease. We have open purchase commitments with third-party contract manufacturers with facilities in Taiwan to supply nearly all of our finished goods inventories, spare parts, and accessories. These purchase orders are expected to be paid within one year of the issuance date. In 2008, we entered into a technology licensing arrangement that requires us to make payments over the life of the associated patents which are expected to expire in 2020. In March 2015, we financed $0.3 million of computer and network related equipment under a capital lease arrangement. As of December 31, 2015, we had $0.3 million outstanding borrowing under this financing agreement. As of December 31, 2015, the aggregate future noncancelable minimum lease and purchase commitments from our contract manufacturing agreements consist of the following (in thousands): Year Ending December 31, Minimum Future Lease Payments For Operating Lease Capital Lease Obligations Purchase Commitments Technology Licensing Agreements Total 2016 $ 2,525 $ 105 $ 6,113 $ 140 $ 8,883 2017 2,033 105 — 140 2,278 2018 1,841 77 — 140 2,058 2019 1,684 — 140 1,824 2020 288 — — 288 $ 8,371 $ 287 $ 6,113 $ 560 $ 15,331 Rent expense was $3.5 million , $3.4 million and $2.9 million in 2015, 2014 and 2013, respectively. Guarantees We have entered into agreements with some of our customers that contain indemnification provisions in the event of claims alleging that our products infringe the intellectual property rights of a third party. Other guarantees or indemnification arrangements include guarantees of product and service performance and standby letters of credit for lease facilities and corporate credit cards. We have not recorded a liability related to these indemnification and guarantee provisions and our guarantees and indemnification arrangements have not had any significant impact on our consolidated financial statements to date.

Equity Award Plans

Equity Award Plans	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Award Plans	Equity Award Plans Equity Incentive Plans 2008 Plan We adopted the 2008 Stock Plan (the "2008 Plan") for the purpose of granting stock-based awards to eligible service providers, which included our employees, directors, and consultants as well as employees and consultants of our subsidiaries. With the establishment of the 2014 Equity Incentive Plan (the "2014 Plan") in March 2014, we terminated the 2008 Plan. Upon such termination, we ceased granting any awards under the 2008 Plan and only options to purchase shares of our Common Stock outstanding as of such date remain under this plan. The remaining shares available for future grant pursuant to options or other stock-based awards under the 2008 Plan were canceled. 2014 Equity Incentive Plan Our 2014 Equity Incentive Plan (the "2014 Plan") was adopted by our board of directors and approved by our stockholders in March 2014. The 2014 Plan provides for the granting of stock options, restricted stock awards ("RSAs"), restricted stock units ("RSUs"), stock appreciation rights, performance units and performance shares to our employees, directors and consultants, and our subsidiary corporations’ employees and consultants. As of December 31, 2014, we had 1,343,743 shares available for future grant. Annually, the shares authorized for the Plan will increase by the lesser of (i) 8,000,000 shares, (ii) 5% of the outstanding shares of common stock on the last day of our immediately preceding fiscal year, or (iii) such other amount as determined by our Board of Directors. On January 1, 2015, the number of shares in the 2014 Plan was increased by 3,078,645 shares, which represents 5% of the prior year end’s common stock outstanding. In addition, effective as of June 10, 2015, our Board of Directors adopted, and our stockholders approved, an amendment and restatement of our 2014 Plan, which increased the number of shares available for issuance under the 2014 Plan by the number of shares subject to awards granted under the 2008 Plan that were canceled or otherwise forfeited or repurchased by us after March 20, 2014. A maximum of additional 8,310,566 shares may become available for issuance under the 2014 Plan as a result of awards granted under the 2008 Plan that are canceled or otherwise forfeited or repurchased. As of December 31, 2015, 1,640,324 shares of our common stock were eligible to be added to the 2014 Plan share reserve in accordance with the amendment and restatement of the 2014 Plan. During the year ended December 31. 2015, we granted 408,500 stock options and 1,798,247 restricted stock units ("RSUs") under the 2014 Plan to our employees, directors and consultants. As of December 31, 2015, we have 3,364,304 shares available for future grant, excluding shares eligible to be added from the 2008 Plan. Vesting periods of awards granted under the 2014 Plan are determined by the board of directors or other committees responsible for administering the 2014 Plan (the "Plan Administrators"). The Plan Administrators determine the contractual terms of awards granted under the 2014 Plan, provided that incentive stock options and stock appreciation rights granted expire no more than ten years from the grant date. In the case of an incentive stock option granted to an employee, who at the time of grant, owns stock representing more than 10% of the total combined voting power of all classes of stock, the exercise price shall be no less than 110% of the fair value per share on the date of grant, and expire five years from the date of grant. For incentive stock options granted to any other employee, and nonstatutory stock options and stock appreciation rights granted to employees, directors or consultants, the per share exercise price shall be no less than 100% of the fair value per share on the date of grant. 2014 Employee Stock Purchase Plan The 2014 Employee Stock Purchase Plan (the "2014 Purchase Plan") was adopted by our board of directors and approved by our stockholders in March 2014. The 2014 Purchase Plan permits eligible employees to acquire shares of our common stock at 85% of the lower of the fair market value of our common stock on the first trading day of each offering period or on the exercise date that occurs at the end of a purchase period. Each offering period is approximately twenty-four months in duration, starting on the first trading day on or after May 21 and November 21 of each year, except for the first offering period, which commenced on March 21, 2014. Each offering period generally consists of four purchase periods and each purchase period will begin after one exercise date and end with the next exercise date approximately six months later, except that the first purchase period of an offering period will begin on the enrollment date of each offering period and end on the next exercise date. If the fair market value of our common stock on the exercise date is less than the fair market value on the first trading day of the offering period, participants will be withdrawn from the then current offering period following their purchase of shares on the purchase date and automatically will be enrolled in the immediately following offering period. Participants may purchase shares of common stock through payroll deductions of up to 15% of their eligible compensation, subject to purchase limits of the lesser of 1,500 shares during each six month purchase period or $25,000 worth of stock for each calendar year in which an option is outstanding. As of December 31, 2014, we had 1,031,316 shares available for future purchase. Under the provisions of the 2014 Purchase Plan, on the first day of each fiscal year, starting with January 1, 2015, the number of shares in the reserve will increase by the lesser of (i) 3,500,000 , (ii) 1% of the outstanding shares of our common stock on the last day of the immediately preceding fiscal year, or (iii) such other amount as determined by our Board of Directors or other committee administering the 2014 Purchase Plan. In January 2015, we increased common shares reserved for future purchase by 615,729 shares in accordance with the provisions of the 2014 Purchase Plan. The participants of the plan purchased 1,105,015 shares during 2015 and as of December 31, 2015, we have 542,030 shares available for future purchase. Early Exercise of Stock Options We have allowed certain of our employees and directors to exercise options granted under the stock option plans prior to vesting. The unvested shares are subject to our repurchase right at the original purchase price. The proceeds from the early exercise of stock options initially are recorded in other non-current liabilities and reclassified to common stock as our repurchase right lapses. As of December 31, 2015 and 2014, 51,884 and 196,217 shares held by employees and directors were subject to repurchase at an aggregate price of $0.3 million and $1.0 million . Option Exchange Program On November 19, 2015, we commenced an option exchange which permitted employees and service providers to surrender certain outstanding stock options for cancellation in exchange for the grant of replacement RSUs covering a lesser number of shares, subject to a different vesting schedule. This option exchange was completed on December 17, 2015. A total of 344,248 options to purchase shares of common stock with a weighted-average exercise price of $13.58 per share were cancelled and replaced with 109,743 RSUs, with per share fair value of $6.76 , on December 17, 2015. The replacement RSUs will start to vest on the one-year anniversary of the RSU grant date. We accounted for this option exchange as a stock option modification in accordance with the provisions of ASC 718 Shared-Based Compensation . We will record incremental expense of $56,000 in addition to the remaining expense attributable to the exchanged stock options to be amortized over the vesting period of the new awards. Stock-based Compensation Stock-based compensation is based on the estimated fair value of awards, net of estimated forfeitures, and recognized over the requisite service period. Total stock-based compensation recognized for stock-based awards granted under the 2014 Plan, the 2008 Plan, and employee stock purchases under the 2014 Purchase Plan for the years ended December 31, 2015, 2014 and 2013 are as follows (in thousands): Years Ended December 31, 2015 2014 2013 Stock-based compensation by type of award: Stock options $ 5,565 $ 5,852 $ 4,282 Restricted stock units 8,871 3,217 — Employee stock purchase plan 2,425 3,290 — $ 16,861 $ 12,359 $ 4,282 Stock-based compensation by category of expense: Cost of revenue $ 1,533 $ 1,063 $ 162 Sales and marketing 7,735 5,829 2,228 Research and development 5,437 3,932 1,356 General and administrative 2,156 1,535 536 Total stock-based compensation $ 16,861 $ 12,359 $ 4,282 As of December 31, 2015, we had $23.9 million in unrecognized stock-based compensation expense, net of estimated forfeitures, related to stock options, unvested RSUs and MSUs and 2014 Purchase Plan awards which will be recognized over a weighted-average period of 2.5 years . Determination of Fair Value We use the Black-Scholes option pricing model to determine the grant date fair value of stock options and stock purchases and generally recognize stock-based compensation expense on a straight-line basis over the requisite service period. The determination of the fair value on the date of grant is affected by the estimated underlying common stock price, as well as assumptions regarding a number of complex and subjective variables. These variables include expected stock price volatility over the term of the awards, actual and projected employee stock option exercise behaviors, risk-free interest rates, and expected dividends. The fair value of the stock options and employee stock purchases were determined using the Black-Scholes option pricing model and assumptions discussed below. Each of these inputs is subjective and generally requires significant judgment to determine. • Expected Term . We estimate the expected life of options based on an analysis of our historical experience of employee exercise and post-vesting termination behavior considered in relation to the contractual life of the option. The expected term for the 2014 Purchase Plan is based on the term of the purchase period. • Risk-Free Interest Rate . The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero coupon U.S. Treasury notes with maturities approximately equal to the expected terms of stock options and shares to be issued under the 2014 Purchase Plan. • Expected Volatility . Due to the limited trading history of our own common stock, we determined the share price volatility factor based on a combination of the historical volatility of our own common stock and the historical volatility of our peer group. • Dividend Rate . The expected dividend was assumed to be zero as we have never paid dividends and have no current plans to do so. We estimate the fair value of RSUs using the closing market price of our common stock on the grant date. Stock Options The following table summarizes our stock option activity and related information as of and for the year ended December 31, 2015 (in thousands, except for years and per share amounts): Number of Shares Underlying Outstanding Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2014 11,084 5.18 7.9 Granted 409 $ 4.84 Exercised (752 ) $ 3.07 Canceled (1) (1,450 ) $ 8.76 Outstanding as of December 31, 2015 9,291 $ 4.78 7.0 $ 20,975 Vested and expected to vest as of December 31, 2015 8,989 $ 4.76 6.9 $ 20,464 Vested and exercisable as of December 31, 2015 5,676 $ 4.19 6.1 $ 15,727 _____________________________________ (1) Common shares granted under the 2008 Plan and canceled after March 21, 2014 are reallocated to the 2014 Plan’s share reserve as they become available for issuance under the 2014 Plan. During 2015, 732,377 shares of the canceled stock options were eligible to be reallocated to the 2014 Plan share reserve. As of December 31, 2015, the aggregate intrinsic value represents the excess of the closing price of our common stock of $6.56 over the exercise price of the outstanding in-the-money options. The following table provides information pertaining to our stock options for the year ended December 31, 2015, 2014 and 2013 (in thousands, except weighted-average fair values): Years Ended December 31, 2015 2014 2013 Total fair value of options granted $ 869 $ 11,683 $ 13,866 Weighted average fair value of options granted $ 2.13 $ 2.79 $ 3.28 Intrinsic value of options exercised $ 2,299 $ 14,863 $ 3,390 The estimated grant-date fair value of our equity-based awards issued to employees was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Years Ended December 31, 2015 2014 2013 Expected term (in years) 4.80 4.82 6.02-6.08 Risk-free interest rate 1.60% 1.80% 1.12%-1.76% Expected volatility 50% 41% 46% Dividend rate —% —% —% Restricted Stock Units We have granted time-based RSUs to our employees, directors and consultants and MSUs to certain executive officers. Time-based Restricted Stock Units A summary of RSU activities for the year ended December 31, 2015, is as follows (in thousands, except years and per share amounts): Number of Shares Weighted Average Grant Date Fair Value Weighted Average Remaining Remaining Service Period (Years) Aggregated Intrinsic Value Outstanding as of December 31, 2014 2,388 $ 8.97 Granted 1,758 $ 5.95 Released (845 ) $ 9.78 Canceled (429 ) $ 8.98 Outstanding as of December 31, 2015 2,872 $ 6.88 1.6 $ 18,840 The aggregate intrinsic value is the amount that would have been received by the unit holders had all RSUs been vested and released on December 31, 2015. This amount will fluctuate based on the market value of our stock The aggregate fair value of RSUs released as of the respective vesting dates was approximately $5.6 million for the year ended December 31, 2015. Market Performance-based Restricted Stock Units We granted MSUs covering 40,000 shares and 540,000 shares of our common stock to certain company executives during the years ended December 31, 2015 and 2014. These MSUs will vest if the closing price of our common stock remains above certain predetermined target prices for 20 consecutive trading days within a 4 -year period following the award’s grant date, subject to continued service by the award holder. No MSUs were vested or were released during the years ended December 31, 2015 and 2014. The following weighted-average assumptions used in the Monte Carlo simulation were as follows: Years Ended December 31, 2015 2014 Expected term (in years) 2.72 2.82 Risk-free interest rate 1.17% 1.40% Expected volatility 35.2% 36.2% Dividend rate —% —% For the year ended December 31, 2015, the estimated weighted average fair value of these market-based units was $0.87 using a Monte Carlo simulation model with the assumptions discussed above. The total aggregated intrinsic value for the MSUs granted was $3.8 million as of December 31, 2015, which represents the total pre-tax intrinsic value (calculated by multiplying our closing stock price on the last trading day of 2015 by the number of non-vested MSUs) that would have been received by the unit holders had all MSUs vested and been released on December 31, 2015. This amount will fluctuate based on the fair market value of our stock. For the year ended December 31, 2014, the estimated weighted average fair value of these market-based units was $0.86 using a Monte Carlo simulation model with the assumptions discussed above. The total aggregated intrinsic value for the MSUs granted was $2.4 million as of December 31, 2014. Employee Stock Purchase Plan The fair value of the option component of the 2014 Purchase Plan awards was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Years Ended December 31, 2015 2014 Expected term (in years) 1.3 1.3 Risk-free interest rate 0.48% 0.26% Expected volatility 40.7% 27.4% Dividend rate —% —%

Net Loss Per Share Attributable

Net Loss Per Share Attributable To Common Stockholders	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Earnings Per Share	Net Loss Per Share Attributable To Common Stockholders Basic net loss per share of common stock is computed by dividing net loss by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share of common stock is computed using the weighted average number of shares of common stock outstanding plus the effect of common stock equivalents, unless the common stock equivalents are anti-dilutive. Potential dilutive common stock includes stock options, restricted stock units and employee stock purchase plan awards. Since we had net losses attributable to common stockholders in the years ended December 31, 2015, 2014 and 2013, none of the stock options, restricted stock units and employee stock purchase plan awards were included in the computation of diluted shares for these periods, as inclusion of such shares would have been anti-dilutive. The following table summarizes the incremental shares of common stock from potentially dilutive securities, calculated using the treasury stock method (in thousands, except for per share data): Years Ended December 31, 2015 2014 2013 Basic and diluted net loss per share attributable to common stockholders Numerator: Net loss attributable to common stockholders $ (40,034 ) $ (35,870 ) $ (29,078 ) Denominator: Weighted-average shares outstanding - basic 62,428 48,682 9,262 Effect of dilutive potential common shares — — — Weighted-average shares outstanding - diluted 62,428 48,682 9,262 Net loss per share attributable to common stockholders: Basic and diluted $ (0.64 ) $ (0.74 ) $ (3.14 ) The following weighted average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive (in thousands): Years Ended December 31, 2015 2014 2013 Redeemable convertible preferred stock and convertible preferred stock (on an as if converted basis) — — 34,462 Stock options, restricted stock units and employee stock purchase plan awards 10,124 6,415 8,498 Common stock subject to repurchase 52 196 341 Convertible preferred stock warrants — — 44 10,176 6,611 43,345

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The geographical breakdown of income (loss) before provision for income taxes is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic loss $ (41,677 ) $ (35,593 ) $ (28,313 ) Foreign income 2,390 2,380 1,857 Loss before provisions for income taxes $ (39,287 ) $ (33,213 ) $ (26,456 ) The provision for income taxes for the years ended December 31, 2015, 2014 and 2013 consists of the following (in thousands): Years Ended December 31, 2015 2014 2013 Current provision for income taxes: State $ 55 $ 24 $ 33 Foreign 675 1,054 599 Total current 730 1,078 632 Deferred tax benefits: Foreign 17 429 8 Total deferred 17 429 8 Provision for income taxes $ 747 $ 1,507 $ 640 The reconciliation of the statutory federal income tax and our effective income tax is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Amount Percentage Amount Percentage Amount Percentage Tax at statutory rate $ (13,358 ) 34.0 % $ (11,292 ) 34.0 % $ (8,995 ) 34.0 % State tax - net of federal benefits 36 (0.1 )% 16 (0.1 )% 22 (0.1 )% Foreign rate differential (422 ) 1.1 % 231 (0.7 )% (115 ) 0.4 % Changes in federal valuation allowance 11,926 (30.4 )% 10,547 (31.8 )% 8,051 (30.4 )% Stock-based compensation 1,845 (4.7 )% 1,041 (3.1 )% 1,230 (4.7 )% Other permanent items 415 (1.1 )% 513 (1.5 )% 346 (1.3 )% Expenses for uncertain tax positions 227 (0.6 )% 330 (1.0 )% 90 (0.3 )% Other 78 (0.1 )% 121 (0.4 )% 11 — % Provision for income taxes $ 747 (1.9 )% $ 1,507 (4.6 )% $ 640 (2.4 )% The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 46,317 $ 41,941 Research and development credits, net of uncertain tax positions 9,517 7,064 Accruals, reserves, and other 17,904 12,526 Stock-based compensation 2,700 1,585 Depreciation and amortization 2,735 2,379 Gross deferred tax assets 79,173 65,495 Valuation allowance (77,643 ) (63,620 ) Total deferred tax assets 1,530 1,875 Deferred tax liabilities: Others (805 ) (1,167 ) Total deferred tax liabilities (805 ) (1,167 ) Net deferred tax assets $ 725 $ 708 On November 20, 2015, the FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes . The ASU is part of the Board’s simplification initiative aimed at reducing complexity in accounting standards and requires companies to classify all deferred tax assets and liabilities, along with any related valuation allowance, as noncurrent on the balance sheet. Although ASU No. 2015-17 isn’t required for public companies to implement until fiscal years beginning after December 15, 2016, early adoption is allowed. We early adopted ASU No. 2015-17 effective December 31, 2015 and have classified $0.7 million of current deferred tax assets from Other current assets to Other assets on the Consolidated Balance Sheets. We consider this change an improvement in the usefulness of information provided to users of our financial statements. We applied this standard prospectively and did not retrospectively adjust any prior periods. The adoption had no impact on our results of operations. Recognition of deferred tax assets is appropriate when realization of these assets is more likely than not. Based upon the weight of available evidence, which includes our historical operating performance and the recorded cumulative net losses in prior fiscal periods, we recorded a full valuation allowance of $77.6 million and $63.6 million against the net U.S. deferred tax assets as of December 31, 2015 and 2014. For the years ended December 31, 2015, 2014 and 2013, the valuation allowance increased by $14.0 million , $11.2 million and $10.4 million , respectively. As of December 31, 2015 and 2014, we had U.S. federal net operating loss carryforwards of $130.6 million and $117.1 million and state net operating loss carryforwards of $68.4 million and $62.6 million . We track the portion of our net operating loss attributable to stock option benefits in accordance with ASC 718 Compensation-Share Compensation , therefore, these amounts are no longer included in our gross or net deferred tax assets. The gross tax benefit of stock options totals $6.2 million at December 31, 2015, and will only be recorded to additional paid in capital when these benefits reduce cash taxes payable. The federal net operating loss carryforwards will expire at various dates beginning in the year ending December 31, 2026 , if not utilized. The state net operating loss carryforwards will expire at various dates beginning in the year ending December 31, 2016 , if not utilized. Additionally, as of December 31, 2015 and 2014, we had U.S. federal research and development credit carryforwards of $6.4 million and $4.9 million and state research and development credit carryforwards of $6.4 million and $4.6 million . The federal credit carryforwards will begin to expire at various dates beginning in 2026 while the state credit carryforwards can be carried over indefinitely. Utilization of the net operating losses and credit carryforwards may be subject to an annual limitation provided for in the Internal Revenue Code Section 382 and similar state codes. Any annual limitation could result in the expiration of net operating loss and credit carryforwards before utilization. With respect to our undistributed foreign subsidiaries' earnings we consider those earnings to be indefinitely reinvested and, accordingly, no related provision for U.S. federal and state income taxes has been provided. Upon distribution of those earnings' in the form of dividends or otherwise, we may be subject to both U.S. income taxes subject to an adjustment for foreign tax credits and withholding taxes in the various countries. As of December 31, 2015 and 2014, the undistributed earnings approximated $3.9 million and $1.8 million , respectively. The determination of the future tax consequence of the remittance of these earnings is not practicable. Uncertain Tax Positions As of December 31, 2015 and 2014, we had gross unrecognized tax benefits of $2.6 million and $2.2 million . We have accrued net interest expense of $1,000 (i.e., there was $14,000 of gross accrued interest expense offset by $13,000 of interest released due to a lapse of statute of limitations) related to unrecognized tax benefits reflected in the consolidated financial statements for the year ended December 31, 2015. Our policy for classifying interest and penalties associated with unrecognized income tax benefits is to include such items in income tax expense. The activity related to the unrecognized tax benefits is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Gross unrecognized tax benefits—beginning balance $ 2,195 $ 1,846 $ 1,463 Increases (decrease) related to tax positions from prior years (4 ) 340 — Increases related to tax positions taken during current year 361 278 383 Decreases related to tax positions taken during the current year — (269 ) — Gross unrecognized tax benefits—ending balance $ 2,552 $ 2,195 $ 1,846 These amounts are related to certain deferred tax assets with a corresponding valuation allowance. As of December 31, 2015, the total amount of unrecognized tax benefits, if recognized, that would affect the effective tax rate is $0.8 million . We believe that there will not be any significant changes in our unrecognized tax benefits in the next 12 months. We are subject to taxation in the United States, various states, and several foreign jurisdictions. Because we have net operating loss and credit carryforwards, there are open statutes of limitations in which federal, state and foreign taxing authorities may examine our tax returns for all years from 2004 through the current period. We are not currently under examination in any major jurisdiction.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Segment Information	Segment Information Operating segments are defined as components of an enterprise about which separate financial information is available that is evaluated regularly by the chief operating decision maker, or decision making group, in deciding how to allocate resources and in assessing performance. Our chief operating decision maker is our Chief Executive Officer who reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. Accordingly, we have a single reportable segment and operating segment structure. The following table represents revenue by geographic regions based on customers' location, as determined by their ship to addresses (in thousands): Years Ended December 31, 2015 2014 2013 United States $ 106,842 $ 85,325 $ 68,127 Japan 35,636 45,787 39,581 Asia Pacific, excluding Japan 23,847 20,434 15,052 EMEA 27,193 19,254 12,087 Other 5,437 8,707 6,891 Total revenue $ 198,955 $ 179,507 $ 141,738 Geographical information relating to our long-lived assets which include property and equipment, net and intangible assets, net as of December 31, 2015 and 2014 was as follows (in thousands): As of December 31, 2015 2014 United States $ 8,062 $ 9,702 Other 1,708 2,075 Total property and equipment, net and intangible assets, net $ 9,770 $ 11,777

Related-party Transactions

Related-party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related-party Transactions	Related-Party Transactions An affiliate of one of our significant stockholders is also acting as a reseller of our products. On May 27, 2015, the significant stockholder reduced its ownership of our common stock, and ceased to be a related party. During the years ended December 31, 2015, 2014 and 2013, we recognized $2.2 million , $2.8 million and $4.4 million total revenue from this reseller. We had gross accounts receivable of $0.4 million from this reseller as of December 31, 2014.

Description of Business and S18

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Basis of Presentation	Description of Business and Basis of Presentation A10 Networks, Inc. (together with our subsidiaries, the “Company”, “we”, “our” or “us”) was incorporated in California in 2004 and reincorporated in Delaware in 2014. We are headquartered in San Jose, California and have wholly-owned subsidiaries throughout the world including Asia and Europe. Our solutions enable enterprises, service providers, Web giants and government organizations to accelerate, secure and optimize the performance of their data center applications and secure their users, applications and infrastructure from internet, web and network threats at scale. During 2015, we offered three software based advanced application networking and network security solutions to address end-customer needs, including Application Delivery Controllers ("ADC") to optimize web and back-office application performance, Carrier Grade Network Address Translation ("CGN") to provide network address and protocol translation services for service provider networks and Threat Protection System ("TPS") for network-wide multi-vector DDoS security protection. Our solutions are cloud-ready and available, in variety of form factors such as optimized hardware appliances, in the cloud as soft
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”). The accompanying consolidated financial statements include the accounts of A10 Networks, Inc., and our wholly owned subsidiaries. All inter-company balances and transactions have been eliminated in consolidation. We had no comprehensive income (loss) other than our net income (loss), hence our comprehensive income (loss) is the same as the net income (loss) for all periods presented. Pursuant to the accounting guidance provided by Accounting Standard Codification ("ASC") 220 Comprehensive Income, we did not present statements of comprehensive income (loss) for the periods presented .
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Those estimates and assumptions affect including revenue recognition and deferred revenue, allowance for doubtful accounts, sales return reserve, valuation of inventory, contingencies and litigation, income taxes and determination of fair value of stock-based compensation. These estimates are based available as of the date of the consolidated financial statements; therefore, actual results could differ from management’s estimates.
Foreign Currency	Foreign Currency The functional currency of our foreign subsidiaries is the U.S. dollar. Transactions denominated in currencies other than the functional currency are remeasured to the functional currency at the average exchange rate in effect during the period. At the end of each reporting period, monetary assets and liabilities are remeasured to the functional currency using exchange rates in effect at the balance sheet date. Non-monetary assets and liabilities are remeasured at historical exchange rates. Gains and losses related to remeasurement are recorded in interest income and other income (expense), net in the Consolidated Statements of Operations.
Vendor Business Concentration	Vendor Business Concentration We rely on third parties to manufacture our hardware appliances and we purchase raw materials from third-party vendors. We outsourced substantially all of our manufacturing services to two independent manufacturers. In addition, we purchase certain strategic component inventory which is consigned to our third-party manufacturers. Other hardware components included in our products are sourced from various suppliers by our manufacturers and are principally industry standard parts and components that are available from multiple vendors.
Concentration of Credit Risk and Significant Customers	Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents and accounts receivable. Our cash and cash equivalents are invested in high-credit quality financial instruments with banks and financial institutions. We believe that the financial institutions that hold our cash and cash equivalents are financially sound and, accordingly, are subject to minimal credit risk. Our bank deposits may be in excess of insured limits provided on such deposits. Our accounts receivable are unsecured and represent amounts due to us based on contractual obligations of our customers. We mitigate credit risk in respect to accounts receivable by performing periodic credit evaluations of our customers to assess the probability of accounts receivable collection based on a number of factors, including past transaction experience with the customer, evaluation of their credit history, limiting the credit extended and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent more than 10% of our total revenue for each period presented, or our gross accounts receivable balance as of each respective balance sheet date.
Cash and Cash Equivalents	Cash and Cash Equivalents We consider all highly liquid investments with maturities of three months or less when purchased to be cash equivalents. Cash and cash equivalents consist of cash on hand and highly liquid investments in money market funds.
Fair Value Measurement	Fair Value Measurement Assets and liabilities recorded at fair value on a recurring basis in the Consolidated Balance Sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or an exit price that would be paid to transfer a liability in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The authoritative guidance on fair value measurements establishes a three-tier fair value hierarchy for disclosure of fair value measurements as follows: Level I —Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date; Level II —Inputs are observable, unadjusted quoted prices in active markets for similar assets or liabilities, unadjusted quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the related assets or liabilities; and Level III —Unobservable inputs that are significant to the measurement of the fair value of the assets or liabilities that are supported by little or no market data. As of December 31, 2015 and 2014, our financial instruments entirely consist of Level I assets. Level I assets include highly liquid money market funds that are included in cash and cash equivalents.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts Accounts receivable are recorded at invoiced amounts, net of allowances for doubtful accounts if applicable, and do not bear interest. We evaluate the collectability of our accounts receivable based on known collection risks and historical experience. In circumstances where we are aware of a specific customer’s inability to meet its financial obligations to us (e.g., bankruptcy filings or substantial downgrading of credit ratings), we record a specific reserve for bad debts against amounts due to reduce the net recognized receivable to the amount we reasonably believe will be collected. For all other customers, we record reserves for bad debts based on the length of time the receivables are past due and our historical experience of collections and write-offs. If circumstances change, such as higher-than-expected defaults or an unexpected material adverse change in a major customer’s ability to meet its financial obligations, our estimate of the recoverability of the amounts due could be reduced by a material amount.
Inventory	Inventory Inventory consists primarily of finished goods and related component parts and is stated at the lower of standard cost, (which approximates actual cost on a first-in, first-out basis), or market value (estimated net realizable value). We evaluate inventory for excess and obsolete products, based on management’s assessment of future demand and market conditions. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. Inventory write downs are included as a component of cost of products revenue in the accompanying Consolidated Statements of Operations.
Property and Equipment, Net	Property and Equipment, Net Property and equipment, including leasehold improvements, are stated at cost, less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the estimated useful lives of the related assets. Depreciation on property and equipment, excluding leasehold improvements, ranges from one to three years. Leasehold improvements are amortized on a straight-line basis over the shorter of the estimated useful lives of the assets or the remaining lease term. Amortization on leasehold improvements ranges from two to eight years.
Revenue Recognition	Revenue Recognition We derive revenue from two sources: (i) products revenue, which includes hardware and perpetual software license revenue; and (ii) services revenue, which include post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, when all of the following criteria are met: persuasive evidence of an arrangement exists, delivery or performance has occurred, the sales price is fixed or determinable, and collection is reasonably assured. We define each of the four criteria above as follows: • Persuasive evidence of an arrangement exists. Evidence of an arrangement consists of a purchase order issued pursuant to the terms and conditions of a master sales agreement. • Delivery or performance has occurred. We use shipping documents or written evidence of customer acceptance, when applicable, to verify delivery or performance. We recognize product revenue upon transfer of title and risk of loss, which primarily is upon shipment to customers. We do not have significant obligations for future performance, such as customer acceptance provisions, rights of return, or pricing credits, associated with our sales. • The sales price is fixed or determinable. We assess whether the sales price is fixed or determinable based on payment terms and whether the sales price is subject to refund or adjustment. Standard payment terms to customers range from 30 to 90 days. • Collection is reasonably assured. We assess probability of collection on a customer-by-customer basis. Our customers are subjected to a credit review process that evaluates their financial condition and ability to pay for products and services. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years. Unearned PCS revenue is included in deferred revenue. Professional service revenue primarily consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Multiple-Element Arrangements Our hardware with the embedded software solutions (which is a proprietary operating system that together with the hardware delivers the functionality desired by our customers), is considered a separate unit of accounting from PCS because it has value to the customer on a standalone basis and our sales arrangements do not include a right of return for delivered products. For multiple-element arrangements, we allocate revenue to each unit of accounting based on an estimated selling price at the inception of the arrangement. The total arrangement consideration is allocated to each separate unit of accounting using the relative selling price method. We limit the amount of revenue recognized for delivered elements to an amount that is not contingent upon future delivery of additional products or service. When applying the relative selling price method, we determine the selling price for each element using (i) vendor-specific objective evidence, or VSOE, of selling price, if available; (ii) third-party evidence, or TPE, of selling price, if VSOE is not available; and (iii) best estimate of selling price, or BESP, if neither VSOE nor TPE is available. • VSOE. We determine VSOE based on our historical pricing and discounting practices for the specific products and services when sold separately. In determining VSOE, we require that a substantial majority of the stand-alone selling prices fall within a reasonably narrow pricing range. • TPE. When VSOE cannot be established for deliverables in multiple-element arrangements, we apply judgment with respect to whether we can establish a selling price based on TPE. TPE is determined based on competitor prices for interchangeable products or services when sold separately to similarly situated customers. However, as our products contain a significant element of proprietary technology and our solutions offer substantially different features and functionality, the comparable pricing of products with similar functionality typically cannot be obtained. Additionally, as we are unable to reliably determine what competitors products’ selling prices are on a stand-alone basis, we are not typically able to determine TPE. • BESP. When we are unable to establish selling price using VSOE or TPE, we use BESP in our allocation of arrangement consideration. The objective of BESP is to determine the price at which we would transact a sale if the product or service was sold regularly on a standalone basis. As we have not been able to establish VSOE or TPE for our products and some of our services, we determine BESP for the purposes of allocating the arrangement, primarily based on historical transaction pricing. Historical transactions are segregated based on our pricing model and go-to-market strategy, which include factors such as the geographies in which our products and services were sold (domestic or international), offering type (product series, and level of support for PCS) and type of sales channel. The determination of BESP is made through consultation with and approval by management. We may occasionally accept returns to address customer satisfaction issues or solution-fit issues even though there is no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period gross revenues. Specific customer returns and allowances are considered within this estimate. Management also analyzes changes in customer demand and acceptance of products when evaluating the adequacy of returns and sales allowances.
Deferred Revenue	Deferred Revenue Deferred product revenue relates to arrangements where not all revenue recognition criteria have been met. Deferred services revenue primarily represents PCS contracts billed in advance and revenue is recognized ratably over the service contract term, typically one to five years. The current portion of deferred revenue represents the amounts that are expected to be recognized as revenue within one year of the Consolidated Balance Sheets date.
Shipping and Handling	Shipping and Handling Shipping charges billed to customers are included in revenue and the related shipping costs are included in cost of revenue in the accompanying consolidated statements of operations.
Research and Development Costs	Research and Development Costs Research and development efforts are focused on new product development and on developing additional functionality for our existing products. These expenses consist of personnel costs, and to a lesser extent, prototype materials, depreciation and certain allocated facilities and information technology infrastructure costs. We expense research and development costs as incurred.
Segment Information	Segment Information Operating segments are components of an enterprise for which separate financial information is available and is evaluated regularly by our chief operating decision maker in deciding how to allocate resources and assessing performance. Our chief operating decision maker is our Chief Executive Officer. Our Chief Executive Officer who reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. Accordingly, we have a single reportable segment and operating segment structure.
Stock-based Compensation	Stock-Based Compensation We recognize stock-based compensation cost for only those shares ultimately expected to vest on a straight-line basis over the requisite service period of the award. We recognize compensation expense for all stock-based payment awards granted to employees, including stock options, restricted stock units (“RSUs”) and purchases under our 2014 Employee Stock Purchase Plan (“2014 Purchase Plan”), based on the estimated fair value on the date of the grant. The fair value of each stock option granted is estimated using the Black-Scholes option pricing model. The fair value of each RSU granted represents the closing price of our common stock on the date of grant. The fair value of purchases under our 2014 Purchase Plan is calculated based on the closing price of our common stock on the date of grant and the value of put and call options estimated using the Black-Scholes option pricing model. Stock-based compensation is recognized on a straight-line basis over the requisite service period, net of estimated forfeitures. We estimate the fair value of market-performance based restricted stock units ("MSUs") using a Monte Carlo simulation model which requires the input of assumptions, including expected term, stock price volatility and the risk-free rate of return. In addition, judgment is also required in estimating the number of stock-based awards that are expected to be forfeited. Forfeitures are estimated based on historical experience at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures differ from those estimates. The assumptions used in calculating the fair value of share-based payment awards represent management’s best estimates, but these estimates involve inherent uncertainties and the application of management’s judgment. As a result, if factors change and we use different assumptions, our stock-based compensation expense could be materially different in the future.
Warranty Costs	Warranty Costs Our appliance hardware and software generally carry a warranty period of 90 days. Estimates of future warranty costs are based on actual historical returns experience and the application of those historical return rates to our in-warranty installed base.
Litigation and Contingencies	Litigation and Contingencies Litigation is comprised of legal expenses incurred in defending ourselves against litigation matters and our change in litigation reserve. Legal expenses are recorded in our Consolidated Statements of Operations as incurred when the legal services are provided.
401K Profit Sharing Plan	401(k) Profit Sharing Plan We have a qualified contributory savings plan under Section 401(k) of the Internal Revenue Code that is offered to all of our United States employees. Participants in the plan may elect to contribute up to $18,000 of their annual compensation to the plan for the 2015 calendar year. Individuals who were 50 or older may contribute an additional $6,000 of their annual income.
Income Taxes	Income Taxes We account for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in our consolidated financial statements or in our tax returns. Estimates and judgments occur in the calculation of certain tax liabilities and in the determination of the recoverability of certain deferred income tax assets, which arise from temporary differences and carryforwards. Deferred income tax assets and liabilities are measured using the currently enacted tax rates that apply to taxable income in effect for the years in which those tax assets are expected to be realized or settled. We regularly assess the likelihood that our deferred tax assets will be recovered from future taxable income and, to the extent we believe, based upon the weight of available evidence, that it is more likely than not that all or a portion of deferred tax assets will not be realized, a valuation allowance is established through an adjustment to income tax expense. The factors used to assess the likelihood of realization of our deferred tax assets include our forecast of future taxable income and available tax planning strategies that could be implemented to realize the net deferred tax assets. Assumptions represent management’s best estimates and involve inherent uncertainties and the application of management’s judgment. We account for uncertainty in income taxes recognized in our consolidated financial statements by regularly reviewing our tax positions and benefits to be realized. We recognize tax liabilities based upon our estimate of whether, and the extent to which, additional taxes will be due when such estimates are more-likely-than-not to be sustained. An uncertain income tax position will not be recognized if it has less than a 50% likelihood of being sustained upon examination by taxing authorities. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board ("FASB") issued Accounting Standard Update ("ASU") No. 2014-09, Revenue from Contracts with Customers , which provides new guidance on the recognition of revenue and states that an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The updated standard will replace most existing revenue recognition guidance in U.S. GAAP when it becomes effective and permits the use of either the retrospective or cumulative effect transition method. The original effective date of this accounting standard was annual reporting periods beginning after December 15, 2016, including interim periods within that reporting period. In August 2015, the FASB issued ASU No. 2015-14, Revenue from Contracts with Customers: Deferral of the Effective Date , which deferred the effective date of the new accounting standard. This updated standard is effective for us on January 1, 2018. We are currently evaluating the impact of the adoption of this accounting standard update on our consolidated financial position or results of operations and method of adoption. In April 2015, the FASB issued 2015-03 Interest—Imputation of Interest (Subtopic 835-30) Simplifying the Presentation of Debt Issuance Costs and during August 2015, the FASB issued ASU No. 2015-15, Presentation and Subsequent Measurement of Debt Issuance Costs Associated with Line-of-Credit Arrangements , which clarifies the treatment of debt issuance costs from line-of-credit arrangements after adoption of ASU No. 2015-03. This accounting guidance requires debt issuance costs be presented on the balance sheet as a direct reduction from the carrying amount of the related debt liability. ASU No. 2015-15 clarifies that the SEC staff would not object to an entity deferring and presenting debt issuance costs as an asset and subsequently amortizing the deferred debt issuance costs ratably over the term of the line-of-credit arrangement, regardless of whether there are any outstanding borrowings on the line-of-credit arrangement. We adopted ASU No. 2015-15 at the beginning of 2016 and this adoption did not have a material effect on our consolidated financial statements. In July 2015, the FASB issued ASU No. 2015-11, Inventory (Topic 330): Simplifying the Measurement of Inventory . Under this accounting guidance, inventory will be measured at the lower of cost and net realizable value and other options that currently exist for market value will be eliminated. ASU No. 2015-11 defines net realizable value as the estimated selling prices in the ordinary course of business, less reasonably predictable costs of completion, disposal, and transportation. No other changes were made to the current guidance on inventory measurement. This accounting guidance is effective for us in the first quarter of 2017. Early adoption is permitted. We are currently evaluating the impact of the adoption of this accounting standard update on our consolidated financial statements. In November 2015, the FASB issued an update to ASU No. 2015-17 Income Taxes: Balance Sheet Classification of Deferred Taxes, requiring all deferred tax assets and liabilities, and any related valuation allowance, to be classified as noncurrent on the balance sheet. The classification change for all deferred taxes as noncurrent simplifies entities’ processes as it eliminates the need to separately identify the net current and net noncurrent deferred tax asset or liability in each jurisdiction and allocate valuation allowances. The new accounting guidance is effective for annual reporting periods beginning after December 15, 2016 and interim periods therein. Early adoption is permitted. Additionally, this guidance may be applied either prospectively or retrospectively to all periods presented. We elected to prospectively adopt the accounting standard in the fourth quarter of 2015. Prior periods in our consolidated financial statements were not retrospectively adjusted.

Description of Business and S19

Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Revenue as Percentage of Total Revenue and Accounts Receivable as Percentage of Total Net Accounts Receivable	Significant customers, including distribution channel partners and direct customers, are those which represent more than 10% of our total revenue for each period presented, or our gross accounts receivable balance as of each respective balance sheet date. Revenue from our significant customers as a percentage of our total revenue for the years ended December 31, 2015, 2014 and 2013 are as follows: Years Ended December 31, 2015 2014 2013 Customers Customer A * 13% * Customer B * * 15% Customer C * * 10% * represents less than 10% of total revenue

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Assets Measured on Recurring Basis	The following table sets forth the fair value of our financial assets measured on a recurring basis by level within the fair value hierarchy (in thousands): December 31, 2015 December 31, 2014 Level 1 Total Level 1 Total Financial Assets Money market funds $ 71,081 $ 71,081 $ 51,047 $ 51,047

Balance Sheet and Statement o21

Balance Sheet and Statement of Operations Components (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Allowance for Doubtful Accounts and Sales Return Reserve	For the years ended December 31, 2015, 2014 and 2013, allowance for doubtful accounts and sales return reserve consisted of the following activity (in thousands): December 31, 2015 December 31, 2014 December 31, 2013 Allowance for doubtful accounts, beginning balance $ 1,904 $ 1,836 $ 1,494 Charged to expenses 1,590 76 1,068 Write-offs (607 ) (8 ) (726 ) Allowance for doubtful accounts, ending balance $ 2,887 $ 1,904 $ 1,836 December 31, 2015 December 31, 2014 December 31, 2013 Sales return reserve, beginning balance $ 1,342 $ 902 $ 500 Charged to revenue 940 858 720 Utilization (1,102 ) (418 ) (318 ) Sales return reserve, ending balance $ 1,180 $ 1,342 $ 902
Schedule of Inventory	Components of inventory as of December 31, 2015 and 2014 are shown below (in thousands): December 31, December 31, Raw materials $ 9,418 $ 9,922 Finished goods 8,873 10,779 Total inventory $ 18,291 $ 20,701
Schedule of Property and Equipment, Net	Components of property and equipment, net as of December 31, 2015 and 2014 are shown below (in thousands): Estimated Useful Life (in Years) December 31, December 31, Equipment 1-3 $ 35,836 $ 30,486 Software 1-3 3,548 3,197 Leasehold improvements Lesser of the term of the lease or the estimated useful life 2,492 1,780 Furniture and fixtures 3 864 860 Construction in progress — 83 201 Property and equipment, gross 42,823 36,524 Less: accumulated depreciation and amortization (33,920 ) (25,744 ) Total property and equipment, net $ 8,903 $ 10,780
Schedule of Deferred Revenue	Deferred revenue as of December 31, 2015 and December 31, 2014 consists of the following (in thousands): December 31, December 31, Deferred revenue: Products $ 3,233 $ 2,379 Services 69,571 54,841 Total deferred revenue 72,804 57,220 Less: current portion (49,572 ) (39,256 ) Non-current portion $ 23,232 $ 17,964
Schedule of accrued liabilities	Accrued liabilities as of December 31, 2015 and December 31, 2014 consists of the following (in thousands): December 31, December 31, Accrued compensation and benefits $ 18,134 $ 14,447 Accrued tax liabilities 4,520 2,554 Other 5,103 5,434 Total accrued liabilities $ 27,757 $ 22,435

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Operating Leased Assets (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Noncancelable Minimum Operating Lease Payments	As of December 31, 2015, the aggregate future noncancelable minimum lease and purchase commitments from our contract manufacturing agreements consist of the following (in thousands): Year Ending December 31, Minimum Future Lease Payments For Operating Lease Capital Lease Obligations Purchase Commitments Technology Licensing Agreements Total 2016 $ 2,525 $ 105 $ 6,113 $ 140 $ 8,883 2017 2,033 105 — 140 2,278 2018 1,841 77 — 140 2,058 2019 1,684 — 140 1,824 2020 288 — — 288 $ 8,371 $ 287 $ 6,113 $ 560 $ 15,331

Equity Award Plans (Tables)

Equity Award Plans (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan	Total stock-based compensation recognized for stock-based awards granted under the 2014 Plan, the 2008 Plan, and employee stock purchases under the 2014 Purchase Plan for the years ended December 31, 2015, 2014 and 2013 are as follows (in thousands): Years Ended December 31, 2015 2014 2013 Stock-based compensation by type of award: Stock options $ 5,565 $ 5,852 $ 4,282 Restricted stock units 8,871 3,217 — Employee stock purchase plan 2,425 3,290 — $ 16,861 $ 12,359 $ 4,282 Stock-based compensation by category of expense: Cost of revenue $ 1,533 $ 1,063 $ 162 Sales and marketing 7,735 5,829 2,228 Research and development 5,437 3,932 1,356 General and administrative 2,156 1,535 536 Total stock-based compensation $ 16,861 $ 12,359 $ 4,282
Summary of Activity under Stock Option Plans	The following table summarizes our stock option activity and related information as of and for the year ended December 31, 2015 (in thousands, except for years and per share amounts): Number of Shares Underlying Outstanding Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (Years) Aggregate Intrinsic Value Outstanding as of December 31, 2014 11,084 5.18 7.9 Granted 409 $ 4.84 Exercised (752 ) $ 3.07 Canceled (1) (1,450 ) $ 8.76 Outstanding as of December 31, 2015 9,291 $ 4.78 7.0 $ 20,975 Vested and expected to vest as of December 31, 2015 8,989 $ 4.76 6.9 $ 20,464 Vested and exercisable as of December 31, 2015 5,676 $ 4.19 6.1 $ 15,727 _____________________________________ (1) Common shares granted under the 2008 Plan and canceled after March 21, 2014 are reallocated to the 2014 Plan’s share reserve as they become available for issuance under the 2014 Plan. During 2015, 732,377 shares of the canceled stock options were eligible to be reallocated to the 2014 Plan share reserve.
Stock Option Information	The following table provides information pertaining to our stock options for the year ended December 31, 2015, 2014 and 2013 (in thousands, except weighted-average fair values): Years Ended December 31, 2015 2014 2013 Total fair value of options granted $ 869 $ 11,683 $ 13,866 Weighted average fair value of options granted $ 2.13 $ 2.79 $ 3.28 Intrinsic value of options exercised $ 2,299 $ 14,863 $ 3,390
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions	The estimated grant-date fair value of our equity-based awards issued to employees was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Years Ended December 31, 2015 2014 2013 Expected term (in years) 4.80 4.82 6.02-6.08 Risk-free interest rate 1.60% 1.80% 1.12%-1.76% Expected volatility 50% 41% 46% Dividend rate —% —% —%
Summary of Restricted Stock Units Activity	A summary of RSU activities for the year ended December 31, 2015, is as follows (in thousands, except years and per share amounts): Number of Shares Weighted Average Grant Date Fair Value Weighted Average Remaining Remaining Service Period (Years) Aggregated Intrinsic Value Outstanding as of December 31, 2014 2,388 $ 8.97 Granted 1,758 $ 5.95 Released (845 ) $ 9.78 Canceled (429 ) $ 8.98 Outstanding as of December 31, 2015 2,872 $ 6.88 1.6 $ 18,840
Schedule of Share-based Payment Award, Equity Instruments Other than Options, Valuation Assumptions	The following weighted-average assumptions used in the Monte Carlo simulation were as follows: Years Ended December 31, 2015 2014 Expected term (in years) 2.72 2.82 Risk-free interest rate 1.17% 1.40% Expected volatility 35.2% 36.2% Dividend rate —% —%
Summary of Valuation Assumptions	The fair value of the option component of the 2014 Purchase Plan awards was estimated at the grant date using the Black-Scholes option pricing model with the following weighted average assumptions: Years Ended December 31, 2015 2014 Expected term (in years) 1.3 1.3 Risk-free interest rate 0.48% 0.26% Expected volatility 40.7% 27.4% Dividend rate —% —%

Net Loss Per Share Attributab24

Net Loss Per Share Attributable To Common Stockholders (Tables)	12 Months Ended
	Dec. 31, 2015
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table summarizes the incremental shares of common stock from potentially dilutive securities, calculated using the treasury stock method (in thousands, except for per share data): Years Ended December 31, 2015 2014 2013 Basic and diluted net loss per share attributable to common stockholders Numerator: Net loss attributable to common stockholders $ (40,034 ) $ (35,870 ) $ (29,078 ) Denominator: Weighted-average shares outstanding - basic 62,428 48,682 9,262 Effect of dilutive potential common shares — — — Weighted-average shares outstanding - diluted 62,428 48,682 9,262 Net loss per share attributable to common stockholders: Basic and diluted $ (0.64 ) $ (0.74 ) $ (3.14 )
Summary of Outstanding Shares of Common Stock Equivalents	The following weighted average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive (in thousands): Years Ended December 31, 2015 2014 2013 Redeemable convertible preferred stock and convertible preferred stock (on an as if converted basis) — — 34,462 Stock options, restricted stock units and employee stock purchase plan awards 10,124 6,415 8,498 Common stock subject to repurchase 52 196 341 Convertible preferred stock warrants — — 44 10,176 6,611 43,345

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Income before Income Tax, Domestic and Foreign	The geographical breakdown of income (loss) before provision for income taxes is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Domestic loss $ (41,677 ) $ (35,593 ) $ (28,313 ) Foreign income 2,390 2,380 1,857 Loss before provisions for income taxes $ (39,287 ) $ (33,213 ) $ (26,456 )
Schedule of Components of Income Tax Expense (Benefit)	The provision for income taxes for the years ended December 31, 2015, 2014 and 2013 consists of the following (in thousands): Years Ended December 31, 2015 2014 2013 Current provision for income taxes: State $ 55 $ 24 $ 33 Foreign 675 1,054 599 Total current 730 1,078 632 Deferred tax benefits: Foreign 17 429 8 Total deferred 17 429 8 Provision for income taxes $ 747 $ 1,507 $ 640
Schedule of Effective Income Tax Rate Reconciliation	The reconciliation of the statutory federal income tax and our effective income tax is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Amount Percentage Amount Percentage Amount Percentage Tax at statutory rate $ (13,358 ) 34.0 % $ (11,292 ) 34.0 % $ (8,995 ) 34.0 % State tax - net of federal benefits 36 (0.1 )% 16 (0.1 )% 22 (0.1 )% Foreign rate differential (422 ) 1.1 % 231 (0.7 )% (115 ) 0.4 % Changes in federal valuation allowance 11,926 (30.4 )% 10,547 (31.8 )% 8,051 (30.4 )% Stock-based compensation 1,845 (4.7 )% 1,041 (3.1 )% 1,230 (4.7 )% Other permanent items 415 (1.1 )% 513 (1.5 )% 346 (1.3 )% Expenses for uncertain tax positions 227 (0.6 )% 330 (1.0 )% 90 (0.3 )% Other 78 (0.1 )% 121 (0.4 )% 11 — % Provision for income taxes $ 747 (1.9 )% $ 1,507 (4.6 )% $ 640 (2.4 )%
Schedule of Deferred Tax Assets and Liabilities	The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows (in thousands): As of December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 46,317 $ 41,941 Research and development credits, net of uncertain tax positions 9,517 7,064 Accruals, reserves, and other 17,904 12,526 Stock-based compensation 2,700 1,585 Depreciation and amortization 2,735 2,379 Gross deferred tax assets 79,173 65,495 Valuation allowance (77,643 ) (63,620 ) Total deferred tax assets 1,530 1,875 Deferred tax liabilities: Others (805 ) (1,167 ) Total deferred tax liabilities (805 ) (1,167 ) Net deferred tax assets $ 725 $ 708
Summary of Income Tax Contingencies	The activity related to the unrecognized tax benefits is as follows (in thousands): Years Ended December 31, 2015 2014 2013 Gross unrecognized tax benefits—beginning balance $ 2,195 $ 1,846 $ 1,463 Increases (decrease) related to tax positions from prior years (4 ) 340 — Increases related to tax positions taken during current year 361 278 383 Decreases related to tax positions taken during the current year — (269 ) — Gross unrecognized tax benefits—ending balance $ 2,552 $ 2,195 $ 1,846

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2015
Segment Reporting [Abstract]
Schedule of Total Revenue Based on Customer's Location	The following table represents revenue by geographic regions based on customers' location, as determined by their ship to addresses (in thousands): Years Ended December 31, 2015 2014 2013 United States $ 106,842 $ 85,325 $ 68,127 Japan 35,636 45,787 39,581 Asia Pacific, excluding Japan 23,847 20,434 15,052 EMEA 27,193 19,254 12,087 Other 5,437 8,707 6,891 Total revenue $ 198,955 $ 179,507 $ 141,738
Schedule of Long-lived Assets, Net by Location	Geographical information relating to our long-lived assets which include property and equipment, net and intangible assets, net as of December 31, 2015 and 2014 was as follows (in thousands): As of December 31, 2015 2014 United States $ 8,062 $ 9,702 Other 1,708 2,075 Total property and equipment, net and intangible assets, net $ 9,770 $ 11,777

Description of Business and S27

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Foreign exchange loss recorded		$ (500,000)	$ (2,000,000)	$ (2,100,000)
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount	$ 18,000
Cash held in bank accounts	98,117,000	$ 91,905,000	$ 20,793,000	$ 23,867,000
Defined Contribution Plan, Maximum Annual Contribution per Employee, Additional Amount Allowed	6,000
Defined Benefit Plan, Contributions by Employer	$ 800,000

Description of Business and S28

Description of Business and Summary of Significant Accounting Policies - Schedule of Revenue as Percentage of Total Revenue and Accounts Receivable as Percentage of Total Net Accounts Receivable (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Customer D [Member] | Accounts Receivable, Net
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers	27.00%
Customer A | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers		13.00%
Customer A | Accounts Receivable, Net
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers	11.00%
Customer B | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers			15.00%
Customer C | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers			10.00%

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets (Detail) - Fair Value, Measurements, Recurring - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Financial Assets
Realized gains or losses	$ 0	$ 0
Money Market Funds
Financial Assets
Assets at fair value	71,081,000	51,047,000
Money Market Funds | Level I
Financial Assets
Assets at fair value	$ 71,081,000	$ 51,047,000

Balance Sheet and Statement o30

Balance Sheet and Statement of Operations Components - Schedule of Allowance for Doubtful Accounts and Sales Return Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Doubtful Accounts
Valuation Allowance [Line Items]
Valuation Allowances and Reserves, Beginning Balance	$ 1,904	$ 1,836	$ 1,494
Valuation Allowances and Reserves, Charged to Cost and Expense	1,590	76	1,068
Valuation Allowances and Reserves, Write-off	(607)	(8)	(726)
Valuation Allowances and Reserves, Ending Balance	2,887	1,904	1,836
Allowance for Sales Returns
Valuation Allowance [Line Items]
Valuation Allowances and Reserves, Beginning Balance	1,342	902	500
Valuation Allowances and Reserves, Charged to Expense	940	858	720
Valuation Allowances and Reserves, Write-off	(1,102)	(418)	(318)
Valuation Allowances and Reserves, Ending Balance	$ 1,180	$ 1,342	$ 902

Balance Sheet and Statement o31

Balance Sheet and Statement of Operations Components - Schedule of Inventory (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Raw materials	$ 9,418	$ 9,922
Finished goods	8,873	10,779
Total inventory	$ 18,291	$ 20,701

Balance Sheet and Statement o32

Balance Sheet and Statement of Operations Components - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 42,823	$ 36,524
Less: accumulated depreciation and amortization	(33,920)	(25,744)
Total property and equipment, net	8,903	10,780
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	35,836	30,486
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,548	3,197
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 2,492	1,780
Furniture and fixtures
Property Plant And Equipment [Line Items]
Estimated Useful Life (in Years)	3 years
Property and equipment, gross	$ 864	860
Construction in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 83	$ 201
Minimum | Equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life (in Years)	1 year
Minimum | Software
Property Plant And Equipment [Line Items]
Estimated Useful Life (in Years)	1 year
Maximum | Equipment
Property Plant And Equipment [Line Items]
Estimated Useful Life (in Years)	3 years
Maximum | Software
Property Plant And Equipment [Line Items]
Estimated Useful Life (in Years)	3 years

Balance Sheet and Statement o33

Balance Sheet and Statement of Operations Components - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 72,804	$ 57,220
Less: current portion	(49,572)	(39,256)
Non-current portion	23,232	17,964
Products
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	3,233	2,379
Services
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 69,571	$ 54,841

Balance Sheet and Statement o34

Balance Sheet and Statement of Operations Components - Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Accrued compensation and benefits	$ 18,134	$ 14,447
Accrued tax liabilities	4,520	2,554
Other	5,103	5,434
Total accrued liabilities	$ 27,757	$ 22,435

Balance Sheet and Statement o35

Balance Sheet and Statement of Operations Components - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation and amortization property and equipment		$ 8,600	$ 10,000	$ 6,900
Foreign exchange loss recorded			(500)	(2,000)	$ (2,100)
Contractual liability						$ 12,000
Payments related to settlement	$ 5,000
Benefit to litigation expense	$ 7,000	$ 0	$ 6,993	$ 0

Credit Facility (Details)

Credit Facility (Details) - USD ($)	1 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Principal payments on revolving credit facility		$ 0	$ 20,000,000	$ 20,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument term	3 years
Maximum borrowing capacity	$ 35,000,000
Amount outstanding		$ 0	0
Quarterly facility fees		0.45%
Debt issuance costs	$ 1,000,000
Unamortized debt issuance costs		$ 300,000	$ 500,000
Revolving Credit Facility | Alternate Base Rate | Minimum
Line of Credit Facility [Line Items]
Variable interest rate	1.75%
Revolving Credit Facility | Alternate Base Rate | Maximum
Line of Credit Facility [Line Items]
Variable interest rate	2.50%
Revolving Credit Facility | LIBOR | Minimum
Line of Credit Facility [Line Items]
Variable interest rate	2.75%
Revolving Credit Facility | LIBOR | Maximum
Line of Credit Facility [Line Items]
Variable interest rate	3.50%
Revolving Credit Facility | Federal Funds Rate
Line of Credit Facility [Line Items]
Variable interest rate	0.50%
Revolving Credit Facility | Eurodollar
Line of Credit Facility [Line Items]
Variable interest rate	1.00%
Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 10,000,000

Commitments and Contingencies37

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2015
Loss Contingencies [Line Items]
Computer and network related equipment under capital lease arrangements				$ 300
Outstanding borrowings under capital lease	$ 300
Litigation expense (benefit)	2,204	$ (2,837)	$ 11,525
Rent expense	$ 3,500	$ 3,400	$ 2,900

Commitments and Contingencies38

Commitments and Contingencies - Lease Obligations and Other Commitments (Details) $ in Thousands	Dec. 31, 2015USD ($)
Operating Leased Assets [Line Items]
2,016	$ 8,883
2,017	2,278
2,018	2,058
2,019	1,824
2,020	288
Minimum Future Lease Payments	15,331
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum capital lease obligations	300
Capital Lease Obligations
Operating Leased Assets [Line Items]
2,016	2,525
2,017	2,033
2,018	1,841
2,019	1,684
2,020	288
Minimum Future Lease Payments	8,371
Capital Lease Obligations
Capital Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,016	105
2,017	105
2,018	77
Minimum capital lease obligations	287
Purchase Commitments
Operating Leased Assets [Line Items]
2,016	6,113
2,017	0
2,018	0
2,019	0
2,020	0
Minimum Future Lease Payments	6,113
Technology Licensing Agreements
Operating Leased Assets [Line Items]
2,016	140
2,017	140
2,018	140
2,019	140
2,020	0
Minimum Future Lease Payments	$ 560

Equity Award Plans - Additional

Equity Award Plans - Additional Information (Details) - USD ($)	Dec. 17, 2015	Jun. 10, 2015	Jan. 01, 2015	Jan. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Canceled Shares Available for Reallocation		8,310,566				732,377
Share Price						$ 6.56
Options granted to employees and consultants						409,000
Total compensation expense related to unvested awards granted, not yet recognized						$ 23,900,000
Total compensation expense related to unvested awards granted, not yet recognized weighted-average period for recognition						2 years 5 months 25 days
Stock Repurchase Program, Number of Shares Authorized to be Repurchased						51,884	196,217
Stock Repurchase Program, Remaining Authorized Repurchase Amount						$ 300,000	$ 1,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period						1,450,000
Canceled (in dollars per share)						$ 8.76
Two Thousand Fourteen Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares reserved for future issuance						3,500,000
Percentage of outstanding shares of common stock						1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized				615,729
Shares purchased by participants under the 2014 Purchase Plan						1,105,015
Number of shares available for future grant						542,030	1,031,316
Acquisition price at lower of fair market value, percentage						85.00%
Percentage of eligible compensation through payroll deductions						15.00%
Employee maximum number of shares per purchase period						1,500
Employee maximum number of Purchase value of stock per year						$ 25,000
Description of automatic increase in shares reserved for future issuance						On the first day of each fiscal year, starting with January 1, 2015, the number of shares in the reserve will increase by the least of (i) 3,500,000 shares, (ii) 1% of the outstanding shares of our common stock on the last day of the immediately preceeding fiscal year, or (iii) such other amount as determined by our board of directors
Purchase limit of 2014 ESPP description						Purchase limits of 1,500 shares during each six month purchase period or $25,000 worth of stock for each calendar year
Offering period description						Each offering period will be approximately twenty-four months in duration, starting on the first trading day on or after May 21 and November 21 of each year, except for the first offering period, which commenced on March 21, 2014 and will end on the last trading day on or before May 20, 2016
Market Performance-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested						$ 3,800,000	$ 2,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price						$ 0.87	$ 0.86
Granted (in shares)						40,000	540,000
Share-based Compensation Arrangement by Share-based Payment Award, Consecutive Trading Days						20 days
Share-based Compensation Arrangement by Share-based Payment Award, Target Price Measurement Period						4 years
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value						$ 5,600,000
Granted (in dollars per share)						$ 5.95
Granted (in shares)						1,758,000
Two Thousand Fourteen Employee Stock Purchase Plan [Member] | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Description of automatic increase in shares reserved for future issuance						On the first day of each fiscal year, starting with January 1, 2015, the number of shares in the reserve will increase by the least of (i) 8,000,000 shares, (ii) 5% of the outstanding shares of common stock on the last day of our immediately preceding fiscal year, or (iii) such other amount as determined by our board of directors.
Option Exchange Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted (in dollars per share)	$ 6.76
Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period	344,248
Canceled (in dollars per share)	$ 13.58
Granted (in shares)	109,743
2014 Stock Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Additional shares reserved for future issuance						8,000,000
Percentage of outstanding shares of common stock						5.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized			3,078,645			1,640,324
Number of shares available for future grant						3,364,304	1,343,743
Options granted, exercisable term (in years)						5 years
2014 Stock Incentive Plan | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted to employees and consultants						408,500
2014 Stock Incentive Plan | Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted to employees and consultants						1,798,247
2014 Stock Incentive Plan | Performance-based Restricted Stock Units Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting criteria - consecutive trading days required						20 days
Award vesting criteria - vesting period						4 years
2014 Stock Incentive Plan | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of fair value per share on grant date						110.00%
2014 Stock Incentive Plan | Minimum | Non Statutory Stock Option Award
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of exercise price of fair value per share on grant date						100.00%
2014 Stock Incentive Plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options granted, exercisable term (in years)						10 years
Total combined voting power of all classes of stock						10.00%
Scenario, Forecast [Member] | Option Exchange Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Allocated Share-based Compensation Expense					$ 56,000

Equity Award Plans - Schedule o

Equity Award Plans - Schedule of Allocated Share-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 16,861	$ 12,359	$ 4,282
Cost of Revenue
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	1,533	1,063	162
Sales and Marketing
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	7,735	5,829	2,228
Research and Development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	5,437	3,932	1,356
General and Administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	2,156	1,535	536
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	5,565	5,852	4,282
Restricted Stock Units (RSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	8,871	3,217	0
Two Thousand Fourteen Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 2,425	$ 3,290	$ 0

Equity Award Plans - Summary of

Equity Award Plans - Summary of Activity under Stock Option Plans (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Number of shares underlying outstanding options
Outstanding options, Beginning balance	11,084
Granted (in shares)	409
Exercised (in shares)	(752)
Canceled (in shares)	(1,450)
Outstanding options, Ending balance	9,291	11,084
Vested and expected to vest at end of period	8,989
Vested and exercisable (in shares)	5,676
Options Outstanding Weighted-average exercise price
Beginning balance (in dollars per share)	$ 5.18
Granted (in dollars per share)	4.84
Exercised (in dollars per share)	3.07
Canceled (in dollars per share)	8.76
Ending balance (in dollars per share)	4.78	$ 5.18
Vested and expected to vest at end of period (in dollars per share)	4.76
Vested and exercisable at end of period (in dollars per share)	$ 4.19
Weighted-average remaining contractual term, beginning of the period	7 years	7 years 10 months 24 days
Weighted-average remaining contractual term, end of the period	7 years	7 years 10 months 24 days
Weighted average remaining contractual term, Vested and expected to vest at end of period	6 years 10 months 24 days
Weighted average remaining contractual term, Vested and exercisable at end of period	6 years 26 days
Aggregate Intrinsic Value, end of the period	$ 20,975
Aggregate Intrinsic Value, Vested and expected to vest at end of period	20,464
Aggregate Intrinsic Value, Vested and exercisable at end of period	$ 15,727

Equity Award Plans - Informatio

Equity Award Plans - Information About Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total fair value of options granted	$ 869	$ 11,683	$ 13,866
Weighted average fair value of options granted	$ 2.13	$ 2.79	$ 3.28
Intrinsic value of options exercised	$ 2,299	$ 14,863	$ 3,390

Equity Award Plans - Summary 43

Equity Award Plans - Summary of Valuation Assumptions (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Market Performance-Based Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years 8 months 19 days	2 years 9 months 27 days
Risk-free interest rate	1.17%	1.40%
Expected volatility	35.20%	36.20%
Dividend rate	0.00%	0.00%
Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	4 years 9 months 18 days	4 years 9 months 25 days
Risk-free interest rate	1.60%	1.80%
Expected volatility	50.10%	40.52%	46.00%
Dividend rate	0.00%	0.00%	0.00%
Minimum | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			6 years 7 days
Risk-free interest rate			1.12%
Maximum | Stock Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)			6 years 29 days
Risk-free interest rate			1.76%
Two Thousand Fourteen Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	1 year 3 months 20 days	1 year 3 months 20 days
Risk-free interest rate	0.48%	0.26%
Expected volatility	40.70%	27.40%
Dividend rate	0.00%	0.00%

Equity Award Plans - Summary 44

Equity Award Plans - Summary of RSU activity (Details) - Restricted Stock Units (RSUs) [Member] $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning of period (in shares) | shares	2,388
Granted (in shares) | shares	1,758
Released (in shares) | shares	(845)
Canceled (in shares) | shares	(429)
Outstanding at end of period (in shares) | shares	2,872
Weighted Average Grant Date Fair Value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 0
Granted (in dollars per share) | $ / shares	5.95
Released (in dollars per share) | $ / shares	0
Canceled (in dollars per share) | $ / shares	8.98
Outstanding at end of period (in dollars per share) | $ / shares	$ 6.88
Weighted Average Remaining Remaining Service Period (Years)	1 year 7 months 13 days
Aggregated Intrinsic Value | $	$ 18,840

Net Loss Per Share Attributab45

Net Loss Per Share Attributable To Common Stockholders - Summary of Computation of Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share [Abstract]
Net loss attributable to common stockholders	$ (40,034)	$ (35,870)	$ (29,078)
Weighted-average shares outstanding - basic	62,428	48,682	9,262
Effect of dilutive potential common shares	0	0	0
Weighted-average shares outstanding - diluted	62,428	48,682	9,262
Basic and diluted	$ (0.64)	$ (0.74)	$ (3.14)

Net Loss Per Share Attributab46

Net Loss Per Share Attributable To Common Stockholders - Summary of Outstanding Shares of Common Stock Equivalents (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	10,176	6,611	43,345
Convertible Preferred Stock
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	0	0	34,462
Stock Options to Purchase Common Stock
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	10,124	6,415	8,498
Common Stock Subject to Repurchase
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	52	196	341
Convertible Preferred Stock Warrants
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	0	0	44

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income before Income Tax, by Geographic Region (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Domestic loss	$ (41,677)	$ (35,593)	$ (28,313)
Foreign income	2,390	2,380	1,857
Loss before provision for income taxes	$ (39,287)	$ (33,213)	$ (26,456)

Income Taxes - Components of In

Income Taxes - Components of Income Tax Expense (Benefit) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current provision for income taxes:
State	$ 55	$ 24	$ 33
Foreign	675	1,054	599
Total current	730	1,078	632
Deferred tax benefits:
Foreign	17	429	8
Total deferred	17	429	8
Provision for income taxes	$ 747	$ 1,507	$ 640

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Tax at statutory rate	$ (13,358)	$ (11,292)	$ (8,995)
Tax at statutory rate (percent)	34.00%	34.00%	34.00%
State tax - net of federal benefits	$ 36	$ 16	$ 22
State tax - net of federal benefits (percent)	(0.10%)	(0.10%)	(0.10%)
Foreign rate differential	$ (422)	$ 231	$ (115)
Foreign rate differential (percent)	1.10%	(0.70%)	0.40%
Changes in federal valuation allowance	$ 11,926	$ 10,547	$ 8,051
Changes in valuation allowance (percent)	(30.40%)	(31.80%)	(30.40%)
Stock-based compensation	$ 1,845	$ 1,041	$ 1,230
Stock-based compensation (percent)	(4.70%)	(3.10%)	(4.70%)
Other permanent items	$ 415	$ 513	$ 346
Other permanent items (percent)	(1.10%)	(1.50%)	(1.30%)
Expenses for uncertain tax positions	$ 227	$ 330	$ 90
Expenses for uncertain tax positions (percent)	(0.60%)	(1.00%)	(0.30%)
Other	$ 78	$ 121	$ 11
Other (percent)	(0.10%)	(0.40%)	0.00%
Provision for income taxes	$ 747	$ 1,507	$ 640
Provision for income taxes (percent)	(1.90%)	(4.60%)	(2.40%)

Income Taxes - Deferred Tax Ass

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred Tax Assets, Gross [Abstract]
Net operating loss carryforwards	$ 46,317	$ 41,941
Research and development credits, net of uncertain tax positions	9,517	7,064
Accruals, reserves, and other	17,904	12,526
Stock-based compensation	2,700	1,585
Depreciation and amortization	2,735	2,379
Gross deferred tax assets	79,173	65,495
Valuation allowance	(77,643)	(63,620)
Total deferred tax assets	1,530	1,875
Deferred Tax Liabilities, Gross [Abstract]
Others	(805)	(1,167)
Total deferred tax liabilities	(805)	(1,167)
Net deferred tax assets	$ 725	$ 708

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits—beginning balance	$ 2,195	$ 1,846	$ 1,463
Increases (decrease) related to tax positions from prior years	(4)	340	0
Increases related to tax positions taken during current year	361	278	383
Decreases related to tax positions taken during the current year	0	(269)	0
Gross unrecognized tax benefits—ending balance	$ 2,552	$ 2,195	$ 1,846

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Current deferred tax assets reclassified to Other assets	$ 700,000
Valuation allowance	77,643,000	$ 63,620,000
Increase in valuation allowance	14,000,000	11,200,000	$ 10,400,000
Undistributed earnings of foreign subsidiaries	3,900,000	1,800,000
Unrecognized tax benefits	2,552,000	2,195,000	1,846,000	$ 1,463,000
Accrued interest related to unrecognized tax benefits	1,000
Gross accrued interest expense	(4,000)	340,000	$ 0
Unrecognized tax benefits that would affect the effective tax rate	800,000
U.S. Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	130,600,000	117,100,000
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	68,400,000	62,600,000
Research and Development Credit Carryforward | U.S. Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	6,400,000	4,900,000
Research and Development Credit Carryforward | State
Operating Loss Carryforwards [Line Items]
Tax credit carryforward	6,400,000	$ 4,600,000
Stock Options
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	6,200,000
Interest Expense [Member]
Operating Loss Carryforwards [Line Items]
Gross accrued interest expense	14,000
Interest released due to lapse of statue of limitations	$ 13,000

Segment Information - Schedule

Segment Information - Schedule of Total Revenue Based on Customer's Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total revenue	$ 198,955	$ 179,507	$ 141,738
United States
Segment Reporting Information [Line Items]
Total revenue	106,842	85,325	68,127
Japan
Segment Reporting Information [Line Items]
Total revenue	35,636	45,787	39,581
Asia Pacific, excluding Japan
Segment Reporting Information [Line Items]
Total revenue	23,847	20,434	15,052
EMEA
Segment Reporting Information [Line Items]
Total revenue	27,193	19,254	12,087
Other
Segment Reporting Information [Line Items]
Total revenue	$ 5,437	$ 8,707	$ 6,891

Segment Information - Schedul54

Segment Information - Schedule of Long-lived Assets, Net by Location (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Total property and equipment, net and intangible assets, net	$ 9,770	$ 11,777
United States
Segment Reporting Information [Line Items]
Total property and equipment, net and intangible assets, net	8,062	9,702
Other
Segment Reporting Information [Line Items]
Total property and equipment, net and intangible assets, net	$ 1,708	$ 2,075

Related-party Transactions (Det

Related-party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Related Party Transactions [Abstract]
Revenue from related parties	$ 2.2	$ 2.8	$ 4.4
Gross accounts receivable		$ 0.4