A10 Networks (ATEN) 10-Q3 Nov 162016 Q3 Quarterly reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2016	Oct. 28, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
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		67,205,810

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current Assets:
Cash and cash equivalents	$ 31,380	$ 98,117
Marketable securities	85,385	0
Accounts receivable, net of allowances of $4,048 and $4,067 as of September 30, 2016 and December 31, 2015	48,903	57,778
Inventory	14,537	18,291
Prepaid expenses and other current assets	4,652	5,064
Total current assets	184,857	179,250
Property and equipment, net	8,851	8,903
Goodwill and intangible assets	8,300	867
Other non-current assets	3,752	3,531
Total Assets	205,760	192,551
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable	9,419	10,508
Accrued liabilities	29,427	27,757
Deferred revenue, current	53,484	49,572
Total current liabilities	92,330	87,837
Deferred revenue, non-current	29,759	23,232
Other non-current liabilities	1,052	1,414
Total Liabilities	123,141	112,483
Commitments and contingencies (Note 5)
Stockholders' Equity:
Common stock, par value $0.00001 — 500,000 shares authorized as of September 30, 2016 and December 31, 2015; 67,089 and 64,172 shares issued and outstanding as of September 30, 2016 and December 31, 2015	1	1
Additional paid-in capital	323,555	301,886
Accumulated other comprehensive income	36	0
Accumulated deficit	(240,973)	(221,819)
Total Stockholders' Equity	82,619	80,068
Total Liabilities and Stockholders' Equity	$ 205,760	$ 192,551

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 4,048	$ 4,067
Common Stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	67,089,000	64,172,000
Common stock, shares outstanding (in shares)	67,089,000	64,172,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue:
Products	$ 35,275	$ 34,990	$ 110,446	$ 98,837
Services	19,793	15,788	55,556	43,494
Total revenue	55,068	50,778	166,002	142,331
Cost of revenue:
Products	8,795	8,529	27,297	23,501
Services	4,153	4,186	13,087	11,601
Total cost of revenue	12,948	12,715	40,384	35,102
Gross profit	42,120	38,063	125,618	107,229
Operating expenses:
Sales and marketing	24,331	25,774	77,872	75,258
Research and development	15,968	13,562	45,231	41,542
General and administrative	6,305	6,892	20,196	20,122
Litigation and settlement expense	66	469	2,059	1,939
Total operating expenses	46,670	46,697	145,358	138,861
Loss from operations	(4,550)	(8,634)	(19,740)	(31,632)
Other income (expense), net:
Interest expense	(145)	(151)	(397)	(382)
Interest income and other income (expense), net	309	22	1,544	(167)
Total other income (expense), net	164	(129)	1,147	(549)
Loss before income taxes	(4,386)	(8,763)	(18,593)	(32,181)
Provision for income taxes	298	204	561	497
Net loss	$ (4,684)	$ (8,967)	$ (19,154)	$ (32,678)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.07)	$ (0.14)	$ (0.29)	$ (0.53)
Weighted-average shares used in computing net loss per share:
Basic and diluted (in shares)	66,260	62,753	65,146	62,009

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (unaudited) CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (4,684)	$ (8,967)	$ (19,154)	$ (32,678)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on marketable securities	(52)	0	36	0
Comprehensive loss	$ (4,736)	$ (8,967)	$ (19,118)	$ (32,678)

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (19,154)	$ (32,678)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	5,919	6,784
Stock-based compensation	13,069	13,246
Other non-cash items	1,798	1,589
Changes in operating assets and liabilities:
Accounts receivable, net	7,311	11,223
Inventory	2,303	922
Prepaid expenses and other assets	349	(97)
Accounts payable	(878)	(1,086)
Accrued liabilities	906	(1,492)
Deferred revenue	10,440	9,118
Other	(224)	104
Net cash provided by operating activities	21,839	7,633
Cash flows from investing activities:
Purchases of marketable securities	(109,268)	0
Proceeds from sales and maturities of marketable securities	23,787	0
Payment for acquisition	(4,380)	0
Purchases of property and equipment	(4,256)	(2,558)
Purchase of intangible asset	(1,500)	0
Net cash used in investing activities	(95,617)	(2,558)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee equity incentive plans, net of repurchases	7,116	3,238
Other	(75)	306
Net cash provided by financing activities	7,041	3,544
Net increase (decrease) in cash and cash equivalents	(66,737)	8,619
Cash and cash equivalents—beginning of period	98,117	91,905
Cash and cash equivalents—end of period	31,380	100,524
Supplemental Disclosure of Non-Cash Investing and Financing Activities:
Common stock issued under asset purchase agreement	1,313	0
Inventory transfers to property and equipment	1,451	2,213
Purchases of property and equipment included in accounts payable	275	327
Vesting of early exercised stock options	$ 169	$ 366

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Description of Business A10 Networks, Inc. (together with our subsidiaries, the “Company”, “we”, “our” or “us”) was incorporated in California in 2004 and reincorporated in Delaware in March 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. We offer four 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, protocol translation services for service provider networks, Threat Protection System ("TPS") for network-wide multi-vector DDoS security protection and Convergent Firewall ("CFW") for protecting data centers and mobile infrastructure, improving web security, and encrypting site-to-site communications. Our solutions are cloud-ready and available, in a variety of form factors such as optimized hardware appliances, in the cloud as software, and as virtual appliances. Basis of Presentation The accompanying unaudited Condensed 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. The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain notes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as our annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair presentation of our financial information. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The balance sheet as of December 31, 2015 has been derived from audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited Condensed Consolidated Financial Statements should be read in conjunction with our audited Consolidated Financial Statements for the year ended December 31, 2015 , which are included in our Annual Report on Form 10-K for the year ended December 31, 2015. Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the Condensed Consolidated Financial Statements and accompanying notes. Those estimates and assumptions affect revenue recognition and deferred revenue, allowance for doubtful accounts, sales return reserve, valuation of inventory, fair value of marketable securities, contingencies and litigation, acquisition purchase price allocations, accrued liabilities, and determination of fair value of stock-based compensation. These estimates are based on information available as of the date of the Condensed Consolidated Financial Statements; therefore, actual results could differ from management’s estimates. Significant Accounting Policies The following are changes to our significant accounting policies as reported in our Annual Report on Form 10-K for the year ended December 31, 2015. Marketable securities We classify our investments in debt and equity securities as available-for-sale and record these investments at fair value. Investments with an original maturity of three months or less at the date of purchase are considered cash equivalents, while all other investments are classified as current assets (included in marketable securities on the Condensed Consolidated Balance Sheets) based on their availability for use in current operations. Unrealized gains or losses are reported in accumulated other comprehensive loss, net of taxes, in stockholders’ equity. Realized gains and losses are determined based on the specific identification method, and are reflected in our Condensed Consolidated Statements of Operations. Realized gains or losses and charges for other-than-temporary declines in value, if any, on marketable securities are reported in interest income and other income (expense), net as incurred. We regularly review our investment portfolio to identify and evaluate investments that have indicators of possible impairment. Investments are considered impaired when a decline in fair value is judged to be other-than-temporary. If the cost of an individual investment exceeds its fair value, we evaluate, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and our intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, we will record an impairment charge and establish a new cost basis in the investment. Goodwill Goodwill is measured as the excess of consideration transferred and the net of the acquisition date fair value of assets acquired and liabilities assumed in a business acquisition. Goodwill is not amortized for accounting purposes. We review goodwill for possible impairment annually in the fourth quarter or whenever events or changes in circumstances indicate its carrying amount may not be recoverable. For annual goodwill impairment test in all periods to date, we operate under one reporting unit and the fair value of our reporting unit has been determined by our enterprise value. When assessing goodwill for impairment, we first perform a qualitative assessment to determine whether further impairment testing is necessary. If, as a result of its qualitative assessment, it is more-likely-than-not (i.e. greater than 50% chance) that the fair value of our reporting unit is less than its carrying amount, the quantitative impairment test will be required. Otherwise, no further testing will be required. Examples of events and circumstances that might indicate that a reporting unit’s fair value is less than the carrying amount include macro-economic conditions such as (i) a significant adverse change in customer demand or a severe deterioration in the entity’s operating environment and market conditions; (ii) entity-specific events such as increasing costs, declining financial performance, or loss of key personnel; or (iii) other events such as an expectation that a reporting unit will be sold or there will be a sustained decrease in the stock price on either an absolute basis or relative to peers. If it is determined, as a result of the qualitative assessment, that it is more-likely-than-not that the fair value of our reporting unit is less than its carrying amount, we perform a two-step impairment test on goodwill. The first step requires the identification of the reporting units and comparison of the fair value of a reporting unit with our carrying amount, including goodwill. If the fair value of the reporting unit is less than our carrying value, an indication of goodwill impairment exists for the reporting unit, and the second step of the impairment test is performed to compute the amount of the impairment. Under the second step, an impairment loss is recognized for any excess of the carrying amount of the reporting unit's goodwill over the implied fair value of that goodwill. Intangible Assets Intangible assets consist primarily of developed technology, patents and acquired customer relationships resulting from acquisitions. Intangible assets are recorded at fair value and are amortized on a straight-line basis over their estimated useful lives, which range from five to ten years. Impairment of Long-Lived Assets We periodically evaluate whether changes have occurred that would render our long-lived assets not recoverable. If such circumstances arise, we use an estimate of the undiscounted value of expected future operating cash flows to determine whether the long-lived assets are impaired. If the aggregate undiscounted cash flows are less than the carrying amount of the assets, the resulting impairment charge to be recorded is calculated based on the excess of the carrying amount of the assets over the fair value of such assets, with the fair value generally determined based on an estimate of discounted future cash flows. Concentration of Credit Risk and Significant Customers Financial instruments that potentially subject us to concentrations of credit risk consist of cash, cash equivalents, marketable securities and accounts receivable. Our cash, cash equivalents and marketable securities are invested in high-credit quality financial instruments maintained with banks and financial institutions. Management believes that the financial institutions that hold our cash, cash equivalents and marketable securities are financially sound and, accordingly, are subject to minimal credit risk. In some instances, deposits held with banks and financial institutions 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. 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 three and nine months ended September 30, 2016 and 2015 are as follows: Three Months Ended Nine Months Ended 2016 2015 2016 2015 Customer A (a distribution channel partner) 19% * 13% * * represents less than 10% of total revenue As of September 30, 2016 , one distribution channel partner (Customer A) accounted for 22% of our total gross accounts receivable. As of December 31, 2015 , no customer accounted for 10% or more of our total gross accounts receivable. Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (" FASB") issued Accounting Standard Update ("ASU") No. 2016-02, Leases (Topic 842). This new accounting standard primarily requires lessees to recognize most leases on their balance sheets but record expenses on their income statements in a manner similar to current accounting. For lessors, the guidance modifies the classification criteria and the accounting for sales-type and direct financing leases. The guidance is effective for annual periods beginning after December 15, 2018 with early adoption permitted. We are currently evaluating the impact of this guidance on our financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The new guidance requires the recognition of the income tax effects of awards in the income statement when the awards vest or are settled, thus eliminating additional paid in capital pools. The guidance also allows for the employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting. In addition, the guidance allows for a policy election to account for forfeitures as they occur rather than on an estimated basis. This guidance is effective for annual and interim reporting periods of public entities beginning after December 15, 2016 with early adoption permitted. We are currently evaluating the impact of this guidance on our financial statements. In March and April 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) and ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing. These accounting updates provide supplemental adoption guidance and clarification to ASC No. 2014-09 Revenue from Contracts with Customers . ASU No. 2016-08 and ASU No. 2016-10 must be adopted concurrently with the adoption of ASU 2014-09. We are currently evaluating the impact of the adoption of ASU No. 2014-09, ASU No. 2016-08 and ASU No. 2016-10 on our financial statements. There have been no other recent accounting pronouncements or changes in accounting pronouncements during the nine months ended September 30, 2016 , as compared to the recent accounting pronouncements described in our Annual Report on Form 10-K for the year ended December 31, 2015 , that are of significance or potential significance to us.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	9 Months Ended
Marketable Securities and Fair Value Measurements	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements Marketable Securities As of September 30, 2016 , the estimated fair value of our marketable securities, classified as available for sale, are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 11,998 $ 17 $ (1 ) 12,014 Corporate securities 37,043 42 (14 ) 37,071 Commercial paper 20,549 4 (2 ) 20,551 Asset-backed securities 15,740 9 — 15,749 $ 85,330 $ 72 $ (17 ) $ 85,385 For the three and nine months ended September 30, 2016 , realized gains were immaterial. During the three and nine months ended September 30, 2016 , we did not reclassify any amount to earnings from accumulated other comprehensive income related to unrealized gains or losses. We did not have any marketable securities as of December 31, 2015. The following table summarizes the cost and estimated fair value of marketable securities based on contractual maturities as of September 30, 2016 (in thousands): Amortized Cost Fair Value Less than 1 year $ 56,291 $ 56,323 Mature in 1 - 3 years 29,039 29,062 $ 85,330 $ 85,385 All available-for-sale securities have been classified as current, based on management's ability to use the funds in current operations. Marketable securities in an unrealized loss position as of September 30, 2016 consisted of the following (in thousands): Fair Value Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) Corporate securities 8,391 (14 ) Commercial paper $ 5,374 (2 ) $ 16,764 $ (17 ) As of September 30, 2016 , no marketable securities were in a continuous unrealized loss position for more than twelve months. We do not intend to sell any of these investments, and it is not more likely than not that we would be required to sell these investments before recovery of their amortized cost basis, which may be at maturity. As a result, there is no other-than-temporary impairment for these marketable securities as of September 30, 2016 . Fair Value Measurements Our financial instruments consist of cash, cash equivalents, marketable securities, accounts receivable, accounts payable and accrued liabilities. Accounts receivable, accounts payable and accrued liabilities are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment. Our cash equivalents, which include money market funds, are measured and recorded at fair value on a recurring basis. Marketable securities are comprised of certificates of deposit, corporate securities, commercial paper and asset-backed securities and we measure the fair value at the measurement date using the three-tier fair value hierarchy as described below. Assets and liabilities recorded at fair value on a recurring basis in the Condensed 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 for measuring fair value establishes a three-level valuation hierarchy for disclosure of fair value measurements as follows: Level 1 - Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities; Our Level 1 assets consist of highly liquid money market funds that are included in cash and cash equivalents. Level 2 - Inputs are observable, quoted prices for identical assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in inactive markets, 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; Our Level 2 assets consist of certificates of deposit, corporate securities, commercial paper and asset-backed securities. Level 3 - 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. We did not have any Level 3 assets or liabilities as of September 30, 2016 and December 31, 2015 . There were no transfers between Level 1 and Level 2 fair value measurement categories during the three and nine months ended September 30, 2016 . The following is a summary of our cash, cash equivalents and marketable securities measured at fair value on a recurring basis (in thousands): September 30, 2016 December 31, 2015 Cash and Cash Equivalents Marketable Securities Total Cash and Cash Equivalents Marketable Securities Total Cash $ 20,166 $ 20,166 $ 27,036 $ 27,036 Level I Money market funds $ 11,214 $ — $ 11,214 $ 71,081 $ — $ 71,081 11,214 — 11,214 71,081 — 71,081 Level II Certificates of deposit — 12,014 12,014 — — — Corporate securities — 37,071 37,071 — — — Commercial paper — 20,551 20,551 — — — Asset-backed securities — 15,749 15,749 — — — — 85,385 85,385 — — — $ 31,380 $ 85,385 $ 116,765 $ 98,117 $ — $ 98,117

Condensed Consolidated Financia

Condensed Consolidated Financial Statement Details	9 Months Ended
Condensed Consolidated Financial Statement Details	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Condensed Consolidated Financial Statement Details	Condensed Consolidated Financial Statement Details Inventory September 30, December 31, (in thousands) Raw materials $ 6,451 $ 9,418 Finished goods 8,086 8,873 Total inventory $ 14,537 $ 18,291 Property and Equipment, net September 30, December 31, (in thousands) Equipment $ 40,901 $ 35,836 Software 3,801 3,548 Furniture and fixtures 864 864 Leasehold improvements 2,567 2,492 Construction in progress — 83 Property and equipment, gross 48,133 42,823 Less: accumulated depreciation and amortization (39,282 ) (33,920 ) Property and equipment, net $ 8,851 $ 8,903 Depreciation expense on property and equipment was $1.9 million and $2.1 million for the three months ended September 30, 2016 and 2015 , respectively, and $5.6 million and $6.7 million for the nine months ended September 30, 2016 and 2015 , respectively. Goodwill and Intangible Assets Activity related to goodwill for the nine months ended September 30, 2016 is as follows (in thousands): Balance as of December 31, 2015 $ 72 Acquisitions 1,235 Balance as of September 30, 2016 $ 1,307 Purchased intangible assets, net consisted of the following (in thousands): September 30, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Carrying Value Gross Carrying Amount Accumulated Amortization Net Carrying Value Developed technology $ 5,050 $ (253 ) $ 4,797 $ — $ — $ — Customer relationships 1,746 (1,746 ) — 1,746 (1,746 ) — Patents 2,936 (740 ) 2,196 1,436 (641 ) 795 Total $ 9,732 $ (2,739 ) $ 6,993 $ 3,182 $ (2,387 ) $ 795 Amortization expense related to purchased intangible assets was $0.3 million and $33,000 for the three months ended September 30, 2016 and 2015 , respectively, and $0.4 million and $0.1 million for the nine months ended September 30, 2016 and 2015 , respectively. Purchased intangible assets are amortized over a remaining weighted average useful life of 4.9 years. Total future amortization expense for purchased intangible assets as of September 30, 2016 is as follows (in thousands): Fiscal Years Ending December 31, Remainder of 2016 $ 361 2017 1,442 2018 1,442 2019 1,442 2020 1,442 Thereafter 864 $ 6,993 Accrued Liabilities September 30, December 31, (in thousands) Accrued compensation and benefits $ 20,458 $ 18,134 Accrued tax liabilities 2,639 4,520 Other 6,330 5,103 Total accrued liabilities $ 29,427 $ 27,757 Deferred Revenue September 30, December 31, (in thousands) Deferred revenue: Products $ 2,899 $ 3,233 Services 80,344 69,571 Total deferred revenue 83,243 72,804 Less: current portion (53,484 ) (49,572 ) Non-current portion $ 29,759 $ 23,232

Credit Facilities

Credit Facilities	9 Months Ended
Credit Facilities	Sep. 30, 2016
Line of Credit Facility [Abstract]
Credit Facility	Credit Facilities In September 2013, we entered into a credit agreement (the “2013 Credit Facility”) with Royal Bank of Canada, JPMorgan Chase Bank, N.A. and Bank of America, N.A. as lenders. The 2013 Credit Facility provided a three -year, $35.0 million , revolving credit facility, which included a maximum $10.0 million letter of credit facility. We were required to pay quarterly facility fees of 0.45% per annum on the average daily unused portion of the revolving credit facility. We had no outstanding borrowings under the 2013 Credit Facility as of December 31, 2015 or for any period during the nine months ended September 30, 2016 . The 2013 Credit Facility expired on September 30, 2016. In November 2016, we entered into a loan and security agreement (the “2016 Credit Facility”) with Silicon Valley Bank ("SVB"), as lender. The 2016 Credit Facility provides a three -year, $25.0 million revolving credit facility, which includes a maximum of $25.0 million letter of credit facility. The loans bear interest, at our option, at (i) the prime rate reported in The Wall Street Journal, minus 0.50% or (ii) a LIBOR rate determined in accordance with the 2016 Credit Facility, plus 2.50% . We are required to pay customary closing fees, commitment fees and letter of credit fees for a facility of this size and type. Our obligations under the 2016 Credit Facility are secured by substantially all of our assets, excluding our intellectual property. The 2016 Credit Facility contains customary affirmative and negative covenants. Through the date of this filing, we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants.

Appcito Acquisition

Appcito Acquisition	9 Months Ended
Appcito Acquisition	Sep. 30, 2016
Business Combinations [Abstract]
Appcito Acquisition	Appcito Acquisition On June 23, 2016, we entered into an asset purchase agreement with Appcito, Inc. (“Appcito”), a privately held company engaged in providing a unified set of services for applications deployed on cloud infrastructure with facilities located in Santa Clara, California and Bangalore, India. Under the terms of the purchase agreement, we acquired substantially all of the assets of Appcito. This acquisition enhances our position as a comprehensive secure application services leader, and it represents a strategic step in our vision to help our customers become more secure and agile as they bridge traditional and cloud application environments. The total purchase consideration was $6.5 million . The fair value of the total purchase consideration was $6.3 million , which consisted of $5.0 million in cash consideration, less a holdback of $0.7 million to cover any indemnification claims within twelve months of the acquisition date, and 227,404 unregistered shares of our common stock with an aggregated fair value of $1.3 million . We allocated the total purchase consideration to the net assets acquired, including identifiable intangible assets, based on their respective fair values at the acquisition date. The following table summarizes the allocation of the purchase price to the fair value of the assets acquired (in thousands): Developed technology $ 5,050 Goodwill 1,235 Other tangible assets 58 Total assets acquired $ 6,343 Developed technology is amortized on a straight-line basis over the estimated useful life of five years . Goodwill of $1.2 million was recognized as part of this acquisition is attributable primarily to the expected synergies and other benefits from this acquisition including adding to our existing momentum around providing secure application service solutions that meet several key demands like application analytics, visibility, and centralized control. The acquisition is expected to introduce secure application service offerings that span traditional data centers, private clouds, public clouds, and hybrid clouds. We incurred approximately $0.2 million in legal, accounting and other professional fees related to this acquisition, all of which were expensed during the three months ended June 30, 2016. We do not consider the acquisition of Appcito to be material to our results of operations or financial position, and therefore, we are not presenting pro-forma financial information of the combined operations. This acquisition was taxable for income tax purposes, and the acquired assets have been recorded at fair value for both book and income tax purposes. Therefore, no deferred taxes have been recorded. The goodwill of $1.2 million and the $0.2 million of acquisition costs are capitalized and amortized over 15 years for income tax purposes.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
Commitments and Contingencies	Sep. 30, 2016
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. Accordingly, except as disclosed, we have not established reserves or ranges of possible loss related to these proceedings, as at this time in the proceedings, if any, the matters do not relate to a probable loss and/or amounts cannot be reasonably estimated. On January 29, 2015, the Company, 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 alleging violations of the federal Securities Act of 1933 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. On April 6, 2016, all parties entered into a memorandum of understanding reflecting an agreement in principle to settle all claims against all defendants asserted in the action and providing that we will make a payment of $0.8 million , net of the expected proceeds of insurance policies. The parties subsequently executed a stipulation of settlement, dated June 30, 2016, and filed a motion with the Court seeking preliminary approval of the settlement, which was granted on September 15, 2016. The payment was made in October 2016. The final fairness hearing is scheduled to be heard on January 13, 2017. The settlement releases all claims asserted against all defendants and includes the dismissal of all claims against all defendants without any liability or wrongdoing attributed to them. The settlement remains subject to stockholder notice, final court approval and other customary conditions. 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 May 24, 2016, all parties entered into a memorandum of understanding reflecting an agreement in principle to settle all claims against all defendants asserted in the action, which provides that we implement certain corporate governance measures following final settlement approval. The parties subsequently executed a stipulation of settlement, dated August 26, 2016, and filed a motion with the Court seeking preliminary approval of the settlement. On October 20, 2016, the Court issued an order continuing to November 18, 2016 on the motion for preliminary approval, to allow plaintiff to submit certain supplemental briefing. The settlement releases all claims asserted against all defendants and includes the dismissal of all claims against all defendants without any liability or wrongdoing attributed to them. The settlement remains subject to execution of a formal settlement agreement, court approval and other customary conditions. Lease Obligations and Other Commitments We lease various operating spaces in the United States, Asia, and Europe under non-cancelable operating lease arrangements that expire on various dates through April 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 entered into agreements with some of our customers and channel partners 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 the indemnification and guarantee provisions and our guarantees and indemnification arrangements have not had any significant impact on our Condensed Consolidated Financial Statements to date.

Equity Incentive Plans and Stoc

Equity Incentive Plans and Stock-Based Compensation	9 Months Ended
Equity Incentive Plans and Stock-Based Compensation	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Incentive Plans and Stock-Based Compensation	Equity Incentive Plans and Stock-Based Compensation Equity Incentive Plans 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, restricted stock units, stock appreciation rights, performance units and performance shares to our employees, directors and consultants. 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 available from the 2008 Stock Plan (the "2008 Plan") that were or may in the future be canceled or otherwise forfeited or repurchased by us after March 20, 2014. A maximum of 8,310,566 shares may become available from the 2008 Plan for issuance under the 2014 Plan. As of December 31, 2015 , we had 3,364,304 shares available for future grant. Annually, the shares authorized for the 2014 Plan 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. On January 1, 2016, the number of shares in the 2014 Plan was increased by 4,851,535 shares, which consisted of 3,211,211 shares, representing 5% of the prior year end’s common stock outstanding and 1,640,324 shares for awards under our 2008 Plan that had been canceled, forfeited or repurchased by us between March 21, 2014 and December 31, 2015. During the nine months ended September 30, 2016 , we granted 672,000 stock options and 4,272,388 stock awards under the 2014 Plan to our employees, directors and consultants. As of September 30, 2016 , we had 4,312,753 shares available for future grant, excluding shares eligible to be added from the 2008 Plan as a result of awards that have been canceled, forfeited or repurchased by us after December 31, 2015. As of September 30, 2016 , 243,546 shares of our common stock had been added to the 2014 Plan share reserve which represents awards under our 2008 Plan that have been canceled, forfeited or repurchased by us during the nine months ended September 30, 2016 . 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. As of December 31, 2015 , we had 542,030 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 shares, (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. On January 1, 2016, the common shares reserved for future purchase was increased by 642,242 shares in accordance with the provisions of the 2014 Purchase Plan. In June 2016, our Board of Directors adopted, and our stockholders approved an amendment to our 2014 Purchase Plan which removed the automatic annual share increase and increased the number of shares available for issuance under the 2014 Purchase Plan by 4,000,000 shares. Stock-Based Compensation The following tables summarize the allocation of the stock-based compensation expense (in thousands): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Stock-based compensation by type of award: Stock options $ 1,028 $ 1,347 $ 3,209 $ 4,326 Stock awards 3,231 2,412 9,614 6,477 Employee stock purchase rights 329 849 246 2,443 $ 4,588 $ 4,608 $ 13,069 $ 13,246 Stock-based compensation by category of expense: Cost of revenue $ 332 $ 428 $ 921 $ 1,241 Sales and marketing 1,760 2,093 5,577 6,032 Research and development 1,730 1,489 4,251 4,347 General and administrative 766 598 2,320 1,626 $ 4,588 $ 4,608 $ 13,069 $ 13,246 __________________________________________ (1) Our 2014 Purchase Plan provides twenty-four month offering periods which consist of four six-month purchase periods. We record periodic stock-based compensation expense based on estimated contributions determined at the beginning of each offering period and record purchase adjustments for the difference between the estimated and actual contributions at the end of each purchase period. For the purchase period ended on May 20, 2016, the actual contributions were significantly lower than the estimated contributions due to lower stock price which caused more employees to reach the maximum purchase contribution limit. As of September 30, 2016 , we had $30.9 million of unrecognized stock-based compensation expense, net of estimated forfeitures, related to unvested stock-based awards which will be recognized over a weighted average period of 2.6 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. The grant date fair value of RSUs that have time or performance based vesting conditions contingent upon meeting financial and operational targets are equal to the closing market price of our common stock on the grant date. We estimate the grant date fair value of RSUs that have market based vesting conditions using the Monte Carlo simulation method. Stock Options The following tables summarize our stock option activities and related information (in thousands, except for years and per share amounts): Number of Shares Underlying Outstanding Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding as of December 31, 2015 9,291 $ 4.78 Granted 672 $ 5.52 Exercised (1,191 ) $ 4.17 Canceled (1) (562 ) $ 6.20 Outstanding as of September 30, 2016 8,210 $ 4.83 6.4 $ 48,821 Vested and expected to vest as of September 30, 2016 8,063 $ 4.82 6.4 $ 47,985 Vested and exercisable as of September 30, 2016 5,590 $ 4.50 5.7 $ 35,114 __________________________________________ (1) Common shares granted under the 2008 Plan and canceled after March 20, 2014 are reallocated to the 2014 Plan’s share reserve as they become available for issuance under the 2014 Plan. During the nine months ended September 30, 2016, 244 of the canceled stock options were reallocated to the 2014 Plan. As of September 30, 2016 , the aggregate intrinsic value represents the excess of the closing price of our common stock of $10.69 over the exercise price of the outstanding in-the-money options. Nine Months Ended 2016 2015 Fair value of options granted $ 1,603 $ 869 Weighted-average fair value of options granted $ 2.38 $ 2.13 Intrinsic value of options exercised $ 5,003 $ 1,535 We did not grant stock options during the three months ended September 30, 2016 and 2015 . The estimated grant-date fair value of our stock options issued to employees was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Nine Months Ended 2016 2015 Expected term (in years) 4.9 4.8 Risk-free interest rate 1.42% 1.60% Volatility 49% 50% Dividend rate —% —% Stock Awards We have granted time-based stock awards ("RSUs") to our employees, directors and consultants and performance-based stock awards ("PSUs") and market performance-based stock awards ("MSUs") to certain company executives. The following table summarizes our stock award activities (in thousands): RSUs PSUs MSUs Total Outstanding as of December 31, 2015 2,872 — 580 3,452 Granted 3,725 547 — 4,272 Released (915 ) — — (915 ) Canceled (734 ) (29 ) — (763 ) Outstanding as of September 30, 2016 4,948 518 580 6,046 In February 2016, we granted 547,000 PSUs with certain financial and operational targets. These PSUs are also subject to service condition vesting requirements with 25% of the eligible PSUs scheduled to vest on each of the first, second, third and fourth year anniversary of the PSU grant date. We granted MSUs covering 540,000 shares and 40,000 shares of our common stock to certain executives during 2014 and 2015, all of which were outstanding as of September 30, 2016 . 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. The aggregate intrinsic value is the amount that would have been received by the unit holders had all RSUs been vested and released on September 30, 2016 . This amount will fluctuate based on the fair market value of our stock. As of September 30, 2016 , the aggregated intrinsic value for RSUs, MSUs and PSUs was $64.6 million with a weighted-average remaining service period of 2.8 years. Employee Stock Purchase Plan Employees purchased 552,554 shares at an average price of $3.88 and 542,102 shares at an average price of $3.45 for the nine months ended September 30, 2016 and 2015 , respectively. As of September 30, 2016 , 4,317,184 shares were available for future issuance under the 2014 Purchase Plan. The intrinsic value of shares purchased during the nine months ended September 30, 2016 and 2015 was $1.3 million and $1.4 million , respectively. The intrinsic value is calculated as the difference between the market value on the date of purchase and the purchase price of the shares. We did not grant employee stock purchase rights during the three months ended September 30, 2016 and 2015 . The fair value of the employee stock purchase rights granted was estimated at the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions: Nine Months Ended September 30, 2016 2015 Expected term (in years) 1.3 1.2 Risk-free interest rate 0.65% 0.32% Expected volatility 42.6% 39.6% Dividend rate —% —% Stock Repurchase Program On October 27, 2016, we announced that our board of directors authorized a share repurchase program for up to $20.0 million of our common stock over the next 12 months. Under the repurchase authorization, shares may be purchased from time to time, subject to general business and market conditions and other investment opportunities, through open market purchases, privately negotiated transactions or other means. The repurchase authorization may be commenced, suspended or discontinued at any time at our discretion.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
Net Loss Per Share	Sep. 30, 2016
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share The following table sets forth the computation of our basic and diluted net loss per share (in thousands, except per share data): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Basic and diluted net loss per share Numerator: Net loss $ (4,684 ) $ (8,967 ) $ (19,154 ) $ (32,678 ) Denominator: Weighted-average shares outstanding - basic and diluted 66,260 62,753 65,146 62,009 Net loss per share: Basic and diluted $ (0.07 ) $ (0.14 ) $ (0.29 ) $ (0.53 ) The following weighted-average outstanding shares of common stock equivalents were excluded from the computation of diluted net loss per share because including them would have been antidilutive (in thousands): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Stock options, stock awards and employee stock purchase rights 14,163 11,058 12,878 11,063 Common stock subject to repurchase 21 90 21 90 14,184 11,148 12,899 11,153

Income Taxes

Income Taxes	9 Months Ended
Income Taxes	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded income tax expense of $0.3 million and $0.2 million for the three months ended September 30, 2016 and 2015 , respectively, and $0.6 million and $0.5 million for the nine months ended September 30, 2016 and 2015 , respectively, which primarily consisted of foreign taxes. Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the carrying amounts of existing assets and liabilities in the financial statements and their respective tax bases using tax rates expected to be in effect during the years in which the basis differences reverse. We believe it is more likely than not that our federal and state net deferred tax assets will not be fully realized. In assessing the realizability of deferred tax assets, management considers whether it is more likely than not that some portion or all of a deferred tax asset will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible. A valuation allowance is recorded for loss carryforwards and other deferred tax assets where it is more likely than not that such deferred tax assets will not be realized. Accordingly, we continue to maintain a valuation allowance against all of our U.S. and certain foreign net deferred tax assets as of September 30, 2016 . We will continue to maintain a full valuation allowance against our net federal, state and certain foreign deferred tax assets until there is sufficient evidence to support recoverability of our deferred tax assets. We had $3.0 million and $2.6 million of unrecognized tax benefits as of September 30, 2016 and December 31, 2015 . We do not anticipate a material change to our unrecognized tax benefits over the next twelve months. Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business. Accrued interest and penalties related to unrecognized tax benefits are recognized as part of our income tax provision in our Condensed Consolidated Statements of Operations. All tax years remain open and are subject to future examinations by federal, state and foreign tax authorities. We are not under examination in any jurisdiction.

Segment Information

Segment Information	9 Months Ended
Segment Information	Sep. 30, 2016
Segment Reporting [Abstract]
Segment Information	Segment Information 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. The following table represents revenue by geographic areas based on customers' location, as determined by their ship to addresses (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 United States $ 24,297 $ 25,059 $ 85,242 $ 75,365 Japan 16,008 8,764 37,846 24,222 Asia Pacific, excluding Japan 7,434 7,991 21,911 18,122 EMEA 6,046 7,317 16,973 20,372 Other 1,283 1,647 4,030 4,250 Total revenue $ 55,068 $ 50,778 $ 166,002 $ 142,331 No other geographic regions comprised 10% or greater of our revenue for the three and nine months ended September 30, 2016 and 2015 . Our property and equipment, net is primarily located in the United States. No other geographic regions comprise 10% or more of our property and equipment, net as of September 30, 2016 .

Related-Party Transactions

Related-Party Transactions	9 Months Ended
Related-Party Transactions	Sep. 30, 2016
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 nine months ended September 30, 2015 , we recognized $2.2 million of revenue from this reseller while it was a related party.

Description of Business and S18

Description of Business and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business A10 Networks, Inc. (together with our subsidiaries, the “Company”, “we”, “our” or “us”) was incorporated in California in 2004 and reincorporated in Delaware in March 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. We offer four 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, protocol translation services for service provider networks, Threat Protection System ("TPS") for network-wide multi-vector DDoS security protection and Convergent Firewall ("CFW") for protecting data centers and mobile infrastructure, improving web security, and encrypting site-to-site communications. Our solutions are cloud-ready and available, in a variety of form factors such as optimized hardware appliances, in the cloud as software, and as virtual appliances.
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed 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. The accompanying unaudited Condensed Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and following the requirements of the Securities and Exchange Commission (“SEC”) for interim reporting. As permitted under those rules, certain notes or other financial information that are normally required by U.S. GAAP can be condensed or omitted. These financial statements have been prepared on the same basis as our annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair presentation of our financial information. The results of operations for the three and nine months ended September 30, 2016 are not necessarily indicative of the results to be expected for the year ending December 31, 2016 or for any other interim period or for any other future year. The balance sheet as of December 31, 2015 has been derived from audited financial statements at that date but does not include all of the information required by U.S. GAAP for complete financial statements. The accompanying unaudited Condensed Consolidated Financial Statements should be read in conjunction with our audited Consolidated Financial Statements for the year ended December 31, 2015 , which are included in our Annual Report on Form 10-K for the year ended December 31, 2015.
Use of Estimates	Use of Estimates The preparation of the Condensed Consolidated Financial Statements in conformity with U.S. GAAP requires us to make estimates and assumptions that affect the amounts reported in the Condensed Consolidated Financial Statements and accompanying notes. Those estimates and assumptions affect revenue recognition and deferred revenue, allowance for doubtful accounts, sales return reserve, valuation of inventory, fair value of marketable securities, contingencies and litigation, acquisition purchase price allocations, accrued liabilities, and determination of fair value of stock-based compensation. These estimates are based on information available as of the date of the Condensed Consolidated Financial Statements; therefore, actual results could differ from management’s estimates.
Marketable Securities	Marketable securities We classify our investments in debt and equity securities as available-for-sale and record these investments at fair value. Investments with an original maturity of three months or less at the date of purchase are considered cash equivalents, while all other investments are classified as current assets (included in marketable securities on the Condensed Consolidated Balance Sheets) based on their availability for use in current operations. Unrealized gains or losses are reported in accumulated other comprehensive loss, net of taxes, in stockholders’ equity. Realized gains and losses are determined based on the specific identification method, and are reflected in our Condensed Consolidated Statements of Operations. Realized gains or losses and charges for other-than-temporary declines in value, if any, on marketable securities are reported in interest income and other income (expense), net as incurred. We regularly review our investment portfolio to identify and evaluate investments that have indicators of possible impairment. Investments are considered impaired when a decline in fair value is judged to be other-than-temporary. If the cost of an individual investment exceeds its fair value, we evaluate, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and our intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, we will record an impairment charge and establish a new cost basis in the investment.
Goodwill	Goodwill Goodwill is measured as the excess of consideration transferred and the net of the acquisition date fair value of assets acquired and liabilities assumed in a business acquisition. Goodwill is not amortized for accounting purposes. We review goodwill for possible impairment annually in the fourth quarter or whenever events or changes in circumstances indicate its carrying amount may not be recoverable. For annual goodwill impairment test in all periods to date, we operate under one reporting unit and the fair value of our reporting unit has been determined by our enterprise value. When assessing goodwill for impairment, we first perform a qualitative assessment to determine whether further impairment testing is necessary. If, as a result of its qualitative assessment, it is more-likely-than-not (i.e. greater than 50% chance) that the fair value of our reporting unit is less than its carrying amount, the quantitative impairment test will be required. Otherwise, no further testing will be required. Examples of events and circumstances that might indicate that a reporting unit’s fair value is less than the carrying amount include macro-economic conditions such as (i) a significant adverse change in customer demand or a severe deterioration in the entity’s operating environment and market conditions; (ii) entity-specific events such as increasing costs, declining financial performance, or loss of key personnel; or (iii) other events such as an expectation that a reporting unit will be sold or there will be a sustained decrease in the stock price on either an absolute basis or relative to peers. If it is determined, as a result of the qualitative assessment, that it is more-likely-than-not that the fair value of our reporting unit is less than its carrying amount, we perform a two-step impairment test on goodwill. The first step requires the identification of the reporting units and comparison of the fair value of a reporting unit with our carrying amount, including goodwill. If the fair value of the reporting unit is less than our carrying value, an indication of goodwill impairment exists for the reporting unit, and the second step of the impairment test is performed to compute the amount of the impairment. Under the second step, an impairment loss is recognized for any excess of the carrying amount of the reporting unit's goodwill over the implied fair value of that goodwill.
Intangible Assets	Intangible Assets Intangible assets consist primarily of developed technology, patents and acquired customer relationships resulting from acquisitions. Intangible assets are recorded at fair value and are amortized on a straight-line basis over their estimated useful lives, which range from five to ten years.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets We periodically evaluate whether changes have occurred that would render our long-lived assets not recoverable. If such circumstances arise, we use an estimate of the undiscounted value of expected future operating cash flows to determine whether the long-lived assets are impaired. If the aggregate undiscounted cash flows are less than the carrying amount of the assets, the resulting impairment charge to be recorded is calculated based on the excess of the carrying amount of the assets over the fair value of such assets, with the fair value generally determined based on an estimate of discounted future cash flows.
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, marketable securities and accounts receivable. Our cash, cash equivalents and marketable securities are invested in high-credit quality financial instruments maintained with banks and financial institutions. Management believes that the financial institutions that hold our cash, cash equivalents and marketable securities are financially sound and, accordingly, are subject to minimal credit risk. In some instances, deposits held with banks and financial institutions 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. 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.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In February 2016, the Financial Accounting Standards Board (" FASB") issued Accounting Standard Update ("ASU") No. 2016-02, Leases (Topic 842). This new accounting standard primarily requires lessees to recognize most leases on their balance sheets but record expenses on their income statements in a manner similar to current accounting. For lessors, the guidance modifies the classification criteria and the accounting for sales-type and direct financing leases. The guidance is effective for annual periods beginning after December 15, 2018 with early adoption permitted. We are currently evaluating the impact of this guidance on our financial statements. In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting. The new guidance requires the recognition of the income tax effects of awards in the income statement when the awards vest or are settled, thus eliminating additional paid in capital pools. The guidance also allows for the employer to repurchase more of an employee’s shares for tax withholding purposes without triggering liability accounting. In addition, the guidance allows for a policy election to account for forfeitures as they occur rather than on an estimated basis. This guidance is effective for annual and interim reporting periods of public entities beginning after December 15, 2016 with early adoption permitted. We are currently evaluating the impact of this guidance on our financial statements. In March and April 2016, the FASB issued ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations (Reporting Revenue Gross versus Net) and ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing. These accounting updates provide supplemental adoption guidance and clarification to ASC No. 2014-09 Revenue from Contracts with Customers . ASU No. 2016-08 and ASU No. 2016-10 must be adopted concurrently with the adoption of ASU 2014-09. We are currently evaluating the impact of the adoption of ASU No. 2014-09, ASU No. 2016-08 and ASU No. 2016-10 on our financial statements. There have been no other recent accounting pronouncements or changes in accounting pronouncements during the nine months ended September 30, 2016 , as compared to the recent accounting pronouncements described in our Annual Report on Form 10-K for the year ended December 31, 2015 , that are of significance or potential significance to us.

Description of Business and S19

Description of Business and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2016
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	Revenue from our significant customers as a percentage of our total revenue for the three and nine months ended September 30, 2016 and 2015 are as follows: Three Months Ended Nine Months Ended 2016 2015 2016 2015 Customer A (a distribution channel partner) 19% * 13% * * represents less than 10% of total revenue

Marketable Securities and Fai20

Marketable Securities and Fair Value Measurements (Tables)	9 Months Ended
Marketable Securities and Fair Value Measurements (Tables)	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	As of September 30, 2016 , the estimated fair value of our marketable securities, classified as available for sale, are as follows (in thousands): Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 11,998 $ 17 $ (1 ) 12,014 Corporate securities 37,043 42 (14 ) 37,071 Commercial paper 20,549 4 (2 ) 20,551 Asset-backed securities 15,740 9 — 15,749 $ 85,330 $ 72 $ (17 ) $ 85,385
Investments Classified by Contractual Maturity Date	The following table summarizes the cost and estimated fair value of marketable securities based on contractual maturities as of September 30, 2016 (in thousands): Amortized Cost Fair Value Less than 1 year $ 56,291 $ 56,323 Mature in 1 - 3 years 29,039 29,062 $ 85,330 $ 85,385
Schedule of Unrealized Loss on Investments	Marketable securities in an unrealized loss position as of September 30, 2016 consisted of the following (in thousands): Fair Value Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) Corporate securities 8,391 (14 ) Commercial paper $ 5,374 (2 ) $ 16,764 $ (17 )
Schedule of Fair Value of Assets Measured on Recurring Basis	The following is a summary of our cash, cash equivalents and marketable securities measured at fair value on a recurring basis (in thousands): September 30, 2016 December 31, 2015 Cash and Cash Equivalents Marketable Securities Total Cash and Cash Equivalents Marketable Securities Total Cash $ 20,166 $ 20,166 $ 27,036 $ 27,036 Level I Money market funds $ 11,214 $ — $ 11,214 $ 71,081 $ — $ 71,081 11,214 — 11,214 71,081 — 71,081 Level II Certificates of deposit — 12,014 12,014 — — — Corporate securities — 37,071 37,071 — — — Commercial paper — 20,551 20,551 — — — Asset-backed securities — 15,749 15,749 — — — — 85,385 85,385 — — — $ 31,380 $ 85,385 $ 116,765 $ 98,117 $ — $ 98,117

Condensed Consolidated Financ21

Condensed Consolidated Financial Statement Details (Tables)	9 Months Ended
Condensed Consolidated Financial Statement Details (Tables)	Sep. 30, 2016
Property, Plant and Equipment [Abstract]
Schedule of Inventory	September 30, December 31, (in thousands) Raw materials $ 6,451 $ 9,418 Finished goods 8,086 8,873 Total inventory $ 14,537 $ 18,291
Schedule of Property and Equipment, Net	September 30, December 31, (in thousands) Equipment $ 40,901 $ 35,836 Software 3,801 3,548 Furniture and fixtures 864 864 Leasehold improvements 2,567 2,492 Construction in progress — 83 Property and equipment, gross 48,133 42,823 Less: accumulated depreciation and amortization (39,282 ) (33,920 ) Property and equipment, net $ 8,851 $ 8,903
Schedule of Goodwill	Activity related to goodwill for the nine months ended September 30, 2016 is as follows (in thousands): Balance as of December 31, 2015 $ 72 Acquisitions 1,235 Balance as of September 30, 2016 $ 1,307
Schedule of Acquired Intangible Assets	Purchased intangible assets, net consisted of the following (in thousands): September 30, 2016 December 31, 2015 Gross Carrying Amount Accumulated Amortization Net Carrying Value Gross Carrying Amount Accumulated Amortization Net Carrying Value Developed technology $ 5,050 $ (253 ) $ 4,797 $ — $ — $ — Customer relationships 1,746 (1,746 ) — 1,746 (1,746 ) — Patents 2,936 (740 ) 2,196 1,436 (641 ) 795 Total $ 9,732 $ (2,739 ) $ 6,993 $ 3,182 $ (2,387 ) $ 795
Schedule of Future Amortization Expense for Purchased Finite-lived Intangible Assets	Total future amortization expense for purchased intangible assets as of September 30, 2016 is as follows (in thousands): Fiscal Years Ending December 31, Remainder of 2016 $ 361 2017 1,442 2018 1,442 2019 1,442 2020 1,442 Thereafter 864 $ 6,993
Schedule of Accrued Liabilities	September 30, December 31, (in thousands) Accrued compensation and benefits $ 20,458 $ 18,134 Accrued tax liabilities 2,639 4,520 Other 6,330 5,103 Total accrued liabilities $ 29,427 $ 27,757
Schedule of Deferred Revenue	September 30, December 31, (in thousands) Deferred revenue: Products $ 2,899 $ 3,233 Services 80,344 69,571 Total deferred revenue 83,243 72,804 Less: current portion (53,484 ) (49,572 ) Non-current portion $ 29,759 $ 23,232

Appcito Acquisition (Tables)

Appcito Acquisition (Tables)	9 Months Ended
Appcito Acquisition (Tables)	Sep. 30, 2016
Business Combinations [Abstract]
Schedule of Purchase Price Allocation	The following table summarizes the allocation of the purchase price to the fair value of the assets acquired (in thousands): Developed technology $ 5,050 Goodwill 1,235 Other tangible assets 58 Total assets acquired $ 6,343

Equity Incentive Plans and St23

Equity Incentive Plans and Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-based Compensation	The following tables summarize the allocation of the stock-based compensation expense (in thousands): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Stock-based compensation by type of award: Stock options $ 1,028 $ 1,347 $ 3,209 $ 4,326 Stock awards 3,231 2,412 9,614 6,477 Employee stock purchase rights 329 849 246 2,443 $ 4,588 $ 4,608 $ 13,069 $ 13,246 Stock-based compensation by category of expense: Cost of revenue $ 332 $ 428 $ 921 $ 1,241 Sales and marketing 1,760 2,093 5,577 6,032 Research and development 1,730 1,489 4,251 4,347 General and administrative 766 598 2,320 1,626 $ 4,588 $ 4,608 $ 13,069 $ 13,246 __________________________________________ (1) Our 2014 Purchase Plan provides twenty-four month offering periods which consist of four six-month purchase periods. We record periodic stock-based compensation expense based on estimated contributions determined at the beginning of each offering period and record purchase adjustments for the difference between the estimated and actual contributions at the end of each purchase period. For the purchase period ended on May 20, 2016, the actual contributions were significantly lower than the estimated contributions due to lower stock price which caused more employees to reach the maximum purchase contribution limit.
Summary of Activity under Stock Option Plans	The following tables summarize our stock option activities and related information (in thousands, except for years and per share amounts): Number of Shares Underlying Outstanding Options Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term Aggregate Intrinsic Value Outstanding as of December 31, 2015 9,291 $ 4.78 Granted 672 $ 5.52 Exercised (1,191 ) $ 4.17 Canceled (1) (562 ) $ 6.20 Outstanding as of September 30, 2016 8,210 $ 4.83 6.4 $ 48,821 Vested and expected to vest as of September 30, 2016 8,063 $ 4.82 6.4 $ 47,985 Vested and exercisable as of September 30, 2016 5,590 $ 4.50 5.7 $ 35,114 __________________________________________ (1) Common shares granted under the 2008 Plan and canceled after March 20, 2014 are reallocated to the 2014 Plan’s share reserve as they become available for issuance under the 2014 Plan. During the nine months ended September 30, 2016, 244 of the canceled stock options were reallocated to the 2014 Plan.
Stock Option Information	Nine Months Ended 2016 2015 Fair value of options granted $ 1,603 $ 869 Weighted-average fair value of options granted $ 2.38 $ 2.13 Intrinsic value of options exercised $ 5,003 $ 1,535
Stock Options Valuation Assumptions	The estimated grant-date fair value of our stock options issued to employees was calculated using the Black-Scholes option-pricing model, based on the following assumptions: Nine Months Ended 2016 2015 Expected term (in years) 4.9 4.8 Risk-free interest rate 1.42% 1.60% Volatility 49% 50% Dividend rate —% —%
Summary of Restricted Stock Units Activity	The following table summarizes our stock award activities (in thousands): RSUs PSUs MSUs Total Outstanding as of December 31, 2015 2,872 — 580 3,452 Granted 3,725 547 — 4,272 Released (915 ) — — (915 ) Canceled (734 ) (29 ) — (763 ) Outstanding as of September 30, 2016 4,948 518 580 6,046
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	The fair value of the employee stock purchase rights granted was estimated at the grant date using the Black-Scholes option pricing model with the following weighted-average assumptions: Nine Months Ended September 30, 2016 2015 Expected term (in years) 1.3 1.2 Risk-free interest rate 0.65% 0.32% Expected volatility 42.6% 39.6% Dividend rate —% —%

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
Net Loss Per Share (Tables)	Sep. 30, 2016
Earnings Per Share [Abstract]
Summary of Computation of Basic and Diluted Net Loss Per Share	The following table sets forth the computation of our basic and diluted net loss per share (in thousands, except per share data): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Basic and diluted net loss per share Numerator: Net loss $ (4,684 ) $ (8,967 ) $ (19,154 ) $ (32,678 ) Denominator: Weighted-average shares outstanding - basic and diluted 66,260 62,753 65,146 62,009 Net loss per share: Basic and diluted $ (0.07 ) $ (0.14 ) $ (0.29 ) $ (0.53 )
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 because including them would have been antidilutive (in thousands): Three Months Ended Nine Months Ended 2016 2015 2016 2015 Stock options, stock awards and employee stock purchase rights 14,163 11,058 12,878 11,063 Common stock subject to repurchase 21 90 21 90 14,184 11,148 12,899 11,153

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
Segment Information (Tables)	Sep. 30, 2016
Segment Reporting [Abstract]
Schedule of Total Revenue Based on Customer's Location	The following table represents revenue by geographic areas based on customers' location, as determined by their ship to addresses (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 United States $ 24,297 $ 25,059 $ 85,242 $ 75,365 Japan 16,008 8,764 37,846 24,222 Asia Pacific, excluding Japan 7,434 7,991 21,911 18,122 EMEA 6,046 7,317 16,973 20,372 Other 1,283 1,647 4,030 4,250 Total revenue $ 55,068 $ 50,778 $ 166,002 $ 142,331

Description of Business and S26

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business Incorporation, year	2,004
Entity, state of incorporation	Delaware

Description of Business and S27

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) - Customer A	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)	19.00%	13.00%
Accounts Receivable
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)		22.00%

Marketable Securities and Fai28

Marketable Securities and Fair Value Measurements - Estimate of Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 85,330
Gross Unrealized Gains	72
Gross Unrealized Losses	(17)
Fair Value	85,385	$ 0
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	11,998
Gross Unrealized Gains	17
Gross Unrealized Losses	(1)
Fair Value	12,014
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,043
Gross Unrealized Gains	42
Gross Unrealized Losses	(14)
Fair Value	37,071
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,549
Gross Unrealized Gains	4
Gross Unrealized Losses	(2)
Fair Value	20,551
Asset-backed securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,740
Gross Unrealized Gains	9
Gross Unrealized Losses	0
Fair Value	$ 15,749

Marketable Securities and Fai29

Marketable Securities and Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Amortized Cost
Less than 1 year	$ 56,291
Mature in 1 - 3 years	29,039
Amortized Cost	85,330
Fair Value
Less than 1 year	56,323
Mature in 1 - 3 years	29,062
Fair Value	$ 85,385	$ 0

Marketable Securities and Fai30

Marketable Securities and Fair Value Measurements - Securities in Unrealized Loss Position (Details) $ in Thousands	Sep. 30, 2016USD ($)
Schedule of Available-for-sale Securities [Line Items]
Continuous loss position, Fair value	$ 16,764
Continuous loss position, Unrealized losses	(17)
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Continuous loss position, Fair value	2,999
Continuous loss position, Unrealized losses	(1)
Corporate securities
Schedule of Available-for-sale Securities [Line Items]
Continuous loss position, Fair value	8,391
Continuous loss position, Unrealized losses	(14)
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Continuous loss position, Fair value	5,374
Continuous loss position, Unrealized losses	$ (2)

Marketable Securities and Fai31

Marketable Securities and Fair Value Measurements - Schedule of Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Financial Assets
Cash and Cash Equivalents	$ 31,380	$ 98,117
Marketable Securities	85,385	0
Total	116,765	98,117
Level I
Financial Assets
Cash and Cash Equivalents	11,214	71,081
Marketable Securities	0	0
Total	11,214	71,081
Level II
Financial Assets
Cash and Cash Equivalents	0	0
Marketable Securities	85,385	0
Total	85,385	0
Cash
Financial Assets
Cash and Cash Equivalents	20,166	27,036
Total	20,166	27,036
Money market funds \| Level I
Financial Assets
Cash and Cash Equivalents	11,214	71,081
Marketable Securities	0	0
Total	11,214	71,081
Certificates of deposit
Financial Assets
Marketable Securities	12,014
Certificates of deposit \| Level II
Financial Assets
Cash and Cash Equivalents	0	0
Marketable Securities	12,014	0
Total	12,014	0
Corporate securities
Financial Assets
Marketable Securities	37,071
Corporate securities \| Level II
Financial Assets
Cash and Cash Equivalents	0	0
Marketable Securities	37,071	0
Total	37,071	0
Commercial paper
Financial Assets
Marketable Securities	20,551
Commercial paper \| Level II
Financial Assets
Cash and Cash Equivalents	0	0
Marketable Securities	20,551	0
Total	20,551	0
Asset-backed securities
Financial Assets
Marketable Securities	15,749
Asset-backed securities \| Level II
Financial Assets
Cash and Cash Equivalents	0	0
Marketable Securities	15,749	0
Total	$ 15,749	$ 0

Condensed Consolidated Financ32

Condensed Consolidated Financial Statement Details - Schedule of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
Raw materials	$ 6,451	$ 9,418
Finished goods	8,086	8,873
Total inventory	$ 14,537	$ 18,291

Condensed Consolidated Financ33

Condensed Consolidated Financial Statement Details - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 48,133	$ 42,823
Less: accumulated depreciation and amortization	(39,282)	(33,920)
Property and equipment, net	8,851	8,903
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	40,901	35,836
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,801	3,548
Furniture and fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	864	864
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,567	2,492
Construction in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 0	$ 83

Condensed Consolidated Financ34

Condensed Consolidated Financial Statement Details - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Property, Plant and Equipment [Abstract]
Depreciation and amortization property and equipment	$ 1,900,000	$ 2,100,000	$ 5,600,000	$ 6,700,000
Amortization expense related to intangible assets	$ 300,000	$ 33,000	$ 400,000	$ 100,000
Weighted average useful life of purchased intangible assets (in years)			4 years 11 months

Condensed Consolidated Financ35

Condensed Consolidated Financial Statement Details - Goodwill (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Goodwill [Roll Forward]
Balance at beginning of period	$ 72
Acquisitions	1,235
Balance at end of period	$ 1,307

Condensed Consolidated Financ36

Condensed Consolidated Financial Statement Details - Purchased Intangible Assets, net (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 9,732	$ 3,182
Accumulated Amortization	(2,739)	(2,387)
Net Carrying Value	6,993	795
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,050	0
Accumulated Amortization	(253)	0
Net Carrying Value	4,797	0
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	1,746	1,746
Accumulated Amortization	(1,746)	(1,746)
Net Carrying Value	0	0
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,936	1,436
Accumulated Amortization	(740)	(641)
Net Carrying Value	$ 2,196	$ 795

Condensed Consolidated Financ37

Condensed Consolidated Financial Statement Details - Future Amortization Expense of Acquired Intangibles (Details) $ in Thousands	Sep. 30, 2016USD ($)
Property, Plant and Equipment [Abstract]
Remainder of 2016	$ 361
2,017	1,442
2,018	1,442
2,019	1,442
2,020	1,442
Thereafter	864
Total	$ 6,993

Condensed Consolidated Financ38

Condensed Consolidated Financial Statement Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 20,458	$ 18,134
Accrued tax liabilities	2,639	4,520
Other	6,330	5,103
Total accrued liabilities	$ 29,427	$ 27,757

Condensed Consolidated Financ39

Condensed Consolidated Financial Statement Details - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 83,243	$ 72,804
Less: current portion	(53,484)	(49,572)
Non-current portion	29,759	23,232
Products
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	2,899	3,233
Services
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 80,344	$ 69,571

Credit Facilities (Details)

Credit Facilities (Details) - USD ($)	1 Months Ended
Credit Facilities (Details) - USD ($)	Nov. 30, 2016	Sep. 30, 2013	Nov. 03, 2016	Sep. 30, 2016	Dec. 31, 2015
Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument term (in years)		3 years
Maximum borrowing capacity		$ 35,000,000
Quarterly facility fees		0.45%
Amount outstanding				$ 0	$ 0
Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 10,000,000
Subsequent Event \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument term (in years)	3 years
Maximum borrowing capacity	$ 25,000,000
Amount outstanding			$ 0
Subsequent Event \| Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 25,000,000
Prime Rate \| Subsequent Event \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable rate basis spread	0.50%
LIBOR \| Subsequent Event \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable rate basis spread	2.50%

Appcito Acquisition (Details)

Appcito Acquisition (Details) - USD ($) $ in Thousands	Jun. 23, 2016	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Cash consideration			$ 4,380	$ 0
Estimated useful life (in years)			4 years 11 months
Goodwill			$ 1,307		$ 72
Appcito, Inc.
Business Acquisition [Line Items]
Total purchase price consideration	$ 6,500
Fair value of the purchase price consideration	6,300
Cash consideration	5,000
Holdback held to cover indemnification claims	$ 700
Unregistered shares of common stock issued (shares)	227,404
Fair value of common stock issued	$ 1,300
Goodwill	$ 1,235
Legal, accounting and other professional fees incurred		$ 200
Amortization period of acquisition costs (in years)	15 years
Developed technology \| Appcito, Inc.
Business Acquisition [Line Items]
Estimated useful life (in years)	5 years

Appcito Acquisition - Purchase

Appcito Acquisition - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jun. 23, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Goodwill	$ 1,307		$ 72
Appcito, Inc.
Business Acquisition [Line Items]
Developed technology		$ 5,050
Goodwill		1,235
Other tangible assets		58
Total assets acquired		$ 6,343

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	Apr. 06, 2016USD ($)
City of Warren Police and Fire Retirement System v. A10 Networks [Member]
Other Commitments [Line Items]
Settlement awarded against entity	$ 0.8

Equity Incentive Plans and St44

Equity Incentive Plans and Stock-Based Compensation - 2014 Equity Incentive Plan/ESPP (Details) - USD ($) $ / shares in Units, $ in Millions	Jan. 01, 2016	Jun. 10, 2015	Jun. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)				672,000
Other than options granted (in shares)				4,272,000
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for reallocation				243,546
Number of shares available for future grant				4,312,753		3,364,304
Percentage of outstanding shares of common stock	5.00%
Additional shares authorized for future issuance	4,851,535
Options granted (in shares)				672,000
Other than options granted (in shares)				4,272,388
2014 Stock Incentive Plan \| Prior Common Stock Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized for future issuance	3,211,211
2014 Stock Incentive Plan \| Reallocated 2008 Equity Plan Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized for future issuance	1,640,324
2014 Stock Incentive Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for reallocation		8,310,566
Additional shares reserved for future issuance						8,000,000
Percentage of outstanding shares of common stock						5.00%
2014 Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grant						542,030
Additional shares authorized for future issuance	642,242		4,000,000
2014 Employee Stock Purchase Plan \| ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grant				4,317,184
Shares purchased during period				552,554	542,102
Average share price of shares purchased (in dollars per share)				$ 3.88	$ 3.45
Aggregate intrinsic value of shares purchased				$ 1.3	$ 1.4
2014 Employee Stock Purchase Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of outstanding shares of common stock						1.00%
Additional shares authorized for future issuance						3,500,000

Equity Incentive Plans and St45

Equity Incentive Plans and Stock-Based Compensation - Stock-based Compensation (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014	Oct. 27, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total compensation expense related to unvested awards granted, not yet recognized	$ 30,900,000
Total compensation expense related to unvested awards granted, not yet recognized weighted-average period for recognition (in years)	2 years 7 months 2 days
Share Price	$ 10.69
Other than options granted (in shares)	4,272,000
PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted (in shares)	547,000
Vesting percentage	25.00%
MSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other than options granted (in shares)	0	40,000	540,000
Consecutive trading days (in days)	20 days
Target price measurement period (in years)	4 years
RSUs, MSUs, PSUs
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, Outstanding	$ 64,600,000
Weighted average remaining service period (in years)	2 years 9 months 7 days
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for reallocation	243,546
Other than options granted (in shares)	4,272,388
Subsequent Event \| Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount authorized to be repurchased				$ 20,000,000

Equity Incentive Plans and St46

Equity Incentive Plans and Stock-Based Compensation - Schedule of Stock-based Compensation Awards Granted under Stock Option Plan in Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 4,588	$ 4,608	$ 13,069	$ 13,246
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	332	428	921	1,241
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,760	2,093	5,577	6,032
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,730	1,489	4,251	4,347
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	766	598	2,320	1,626
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,028	1,347	3,209	4,326
Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,231	2,412	9,614	6,477
Employee stock purchase rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 329	$ 849	$ 246	$ 2,443

Equity Incentive Plans and St47

Equity Incentive Plans and Stock-Based Compensation - Summary of Activity under Stock Option Plans (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)$ / sharesshares
Number of Shares Underlying Outstanding Options
Outstanding options, Beginning balance (in shares) \| shares	9,291
Granted (in shares) \| shares	672
Exercised (in shares) \| shares	(1,191)
Canceled (in shares) \| shares	(562)
Outstanding options, Ending balance (in shares) \| shares	8,210
Vested and expected to vest at end of period (in shares) \| shares	8,063
Vested and exercisable (in shares) \| shares	5,590
Weighted-Average Exercise Price
Beginning balance (in dollars per share) \| $ / shares	$ 4.78
Granted (in dollars per share) \| $ / shares	5.52
Exercised (in dollars per share) \| $ / shares	4.17
Canceled (in dollars per share) \| $ / shares	6.20
Ending balance (in dollars per share) \| $ / shares	4.83
Vested and expected to vest at end of period (in dollars per share) \| $ / shares	4.82
Vested and exercisable at end of period (in dollars per share) \| $ / shares	$ 4.50
Weighted-average remaining contractual term (in years)	6 years 4 months 24 days
Weighted average remaining contractual term, Vested and expected to vest at end of period (in years)	6 years 4 months 24 days
Weighted average remaining contractual term, Vested and exercisable at end of period (in years)	5 years 8 months 12 days
Aggregate Intrinsic Value \| $	$ 48,821
Aggregate Intrinsic Value, Vested and expected to vest at end of period \| $	47,985
Aggregate Intrinsic Value, Vested and exercisable at end of period \| $	$ 35,114

Equity Incentive Plans and St48

Equity Incentive Plans and Stock-Based Compensation - Information About Stock Options (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Fair value of options granted	$ 1,603	$ 869
Weighted-average fair value of options granted (in dollars per share)	$ 2.38	$ 2.13
Intrinsic value of options exercised	$ 5,003	$ 1,535

Equity Incentive Plans and St49

Equity Incentive Plans and Stock-Based Compensation - Summary of Valuation Assumptions (Details)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	4 years 10 months 24 days	4 years 9 months 18 days
Risk-free interest rate	1.42%	1.60%
Volatility	49.00%	50.00%
Dividend rate	0.00%	0.00%
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	1 year 3 months 18 days	1 year 2 months 12 days
Risk-free interest rate	0.65%	0.32%
Volatility	42.60%	39.60%
Dividend rate	0.00%	0.00%

Equity Incentive Plans and St50

Equity Incentive Plans and Stock-Based Compensation - Summary of RSU activity (Details) - shares	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
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)	3,452,000
Granted (in shares)	4,272,000
Released (in shares)	(915,000)
Canceled (in shares)	(763,000)
Outstanding at end of period (in shares)	6,046,000	3,452,000
RSUs
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)	2,872,000
Granted (in shares)	3,725,000
Released (in shares)	(915,000)
Canceled (in shares)	(734,000)
Outstanding at end of period (in shares)	4,948,000	2,872,000
PSUs
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)	0
Granted (in shares)	547,000
Released (in shares)	0
Canceled (in shares)	(29,000)
Outstanding at end of period (in shares)	518,000	0
MSUs
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)	580,000
Granted (in shares)	0	40,000	540,000
Released (in shares)	0
Canceled (in shares)	0
Outstanding at end of period (in shares)	580,000	580,000

Net Loss Per Share - Summary of

Net Loss Per Share - Summary of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net loss	$ (4,684)	$ (8,967)	$ (19,154)	$ (32,678)
Denominator:
Weighted-average shares outstanding - basic and diluted (in shares)	66,260	62,753	65,146	62,009
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.07)	$ (0.14)	$ (0.29)	$ (0.53)

Net Loss Per Share - Summary 52

Net Loss Per Share - Summary of Outstanding Shares of Common Stock Equivalents (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	14,184	11,148	12,899	11,153
Stock options, stock awards and employee stock purchase rights
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	14,163	11,058	12,878	11,063
Common stock subject to repurchase
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	21	90	21	90

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax expense	$ 298	$ 204	$ 561	$ 497
Unrecognized tax benefits	$ 3,000		$ 3,000		$ 2,600

Segment Information - Schedule

Segment Information - Schedule of Total Revenue Based on Customer's Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Segment Reporting Information [Line Items]
Total revenue	$ 55,068	$ 50,778	$ 166,002	$ 142,331
United States
Segment Reporting Information [Line Items]
Total revenue	24,297	25,059	85,242	75,365
Japan
Segment Reporting Information [Line Items]
Total revenue	16,008	8,764	37,846	24,222
Asia Pacific, excluding Japan
Segment Reporting Information [Line Items]
Total revenue	7,434	7,991	21,911	18,122
EMEA
Segment Reporting Information [Line Items]
Total revenue	6,046	7,317	16,973	20,372
Other
Segment Reporting Information [Line Items]
Total revenue	$ 1,283	$ 1,647	$ 4,030	$ 4,250

Related-Party Transactions (Det

Related-Party Transactions (Details) $ in Millions	9 Months Ended
Related-Party Transactions (Details) $ in Millions	Sep. 30, 2015USD ($)
SIgnificant Stockholder / Reseller
Related Party Transaction [Line Items]
Revenue from related parties	$ 2.2