A10 Networks (ATEN) 10-Q 1 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 25, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
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 Emerging Growth Company	true
Entity Small Business	false
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		73,798,417

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 36,162	$ 46,567
Marketable securities	87,391	84,567
Accounts receivable, net of allowances of $1,003 and $983, respectively	51,084	48,266
Inventory	15,102	17,577
Prepaid expenses and other current assets	13,266	6,825
Total current assets	203,005	203,802
Property and equipment, net	7,994	9,913
Goodwill	1,307	1,307
Intangible assets	4,108	5,190
Other non-current assets	8,380	4,646
Total assets	224,794	224,858
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable	9,630	9,033
Accrued liabilities	20,602	21,835
Deferred revenue	60,653	61,858
Total current liabilities	90,885	92,726
Deferred revenue, non-current	34,202	32,779
Other non-current liabilities	642	967
Total liabilities	125,729	126,472
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock, $0.00001 par value: 500,000 shares authorized; 72,707 and 71,692 shares issued and outstanding, respectively	1	1
Additional paid-in-capital	369,858	355,533
Accumulated other comprehensive loss	(157)	(123)
Accumulated deficit	(270,637)	(257,025)
Total stockholders' equity	99,065	98,386
Total liabilities and stockholders' equity	$ 224,794	$ 224,858

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 1,003	$ 983
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)	72,707,000	71,692,000
Common stock, shares outstanding (in shares)	72,707,000	71,692,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue	$ 60,502	$ 62,005	$ 170,398	$ 179,912
Cost of revenue:
Total cost of revenue	13,014	13,867	38,085	41,410
Gross profit	47,488	48,138	132,313	138,502
Operating expenses:
Sales and marketing	24,539	26,930	77,231	78,754
Research and development	15,505	15,997	49,874	49,529
General and administrative	9,012	6,945	30,464	21,444
Total operating expenses	49,056	49,872	157,569	149,727
Loss from operations	(1,568)	(1,734)	(25,256)	(11,225)
Non-operating income (expense):
Interest expense	(34)	(20)	(99)	(128)
Interest and other income (expense), net	(131)	(37)	6	779
Total non-operating income (expense), net	(165)	(57)	(93)	651
Loss before income taxes	(1,733)	(1,791)	(25,349)	(10,574)
Provision for income taxes	74	454	660	963
Net loss	$ (1,807)	$ (2,245)	$ (26,009)	$ (11,537)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.02)	$ (0.03)	$ (0.36)	$ (0.17)
Weighted-average shares used in computing net loss per share:
Basic and diluted (in shares)	72,707	70,705	72,550	69,688
Products
Revenue:
Total revenue	$ 38,265	$ 40,404	$ 105,638	$ 116,930
Cost of revenue:
Total cost of revenue	8,790	9,357	24,979	28,124
Services
Revenue:
Total revenue	22,237	21,601	64,760	62,982
Cost of revenue:
Total cost of revenue	$ 4,224	$ 4,510	$ 13,106	$ 13,286

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (1,807)	$ (2,245)	$ (26,009)	$ (11,537)
Other comprehensive loss, net of tax:
Unrealized gain (loss) on marketable securities	64	29	(34)	28
Comprehensive loss	$ (1,743)	$ (2,216)	$ (26,043)	$ (11,509)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (26,009)	$ (11,537)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	6,020	6,222
Stock-based compensation	13,055	13,824
Other non-cash items	152	930
Changes in operating assets and liabilities:
Accounts receivable	(3,144)	11,288
Inventory	1,550	(2,513)
Prepaid expenses and other assets	(868)	(2,785)
Accounts payable	806	(1,243)
Accrued and other liabilities	(1,482)	(3,023)
Deferred revenue	4,219	(1,245)
Other	183	102
Net cash (used in) provided by operating activities	(5,518)	10,020
Cash flows from investing activities:
Proceeds from sales of marketable securities	23,194	18,747
Proceeds from maturities of marketable securities	41,732	52,119
Purchases of marketable securities	(67,754)	(69,580)
Purchase of investment	(1,000)	0
Purchases of property and equipment	(2,252)	(4,223)
Net cash used in investing activities	(6,080)	(2,937)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee equity incentive plans	1,269	7,665
Repurchases and retirement of common stock	0	(3,071)
Payment of contingent consideration	0	(650)
Other	(76)	(83)
Net cash provided by financing activities	1,193	3,861
Net (decrease) increase in cash and cash equivalents	(10,405)	10,944
Cash and cash equivalents - beginning of period	46,567	28,975
Cash and cash equivalents - end of period	36,162	39,919
Non-cash investing and financing activities:
Inventory transfers to property and equipment	925	2,368
Purchases of property and equipment included in accounts payable	$ 78	$ 65

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2018
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. We are a leading provider of secure application solutions and services that enable a new generation of intelligently connected companies with the ability to continuously improve cyber protection and digital responsiveness across dynamic Information Technology (“IT”) and network infrastructures. Our product portfolio seeks to address many of the aforementioned challenges and solution requirements. The portfolio consists of six secure application solutions; Thunder Application Delivery Controllers (“ADC”), Lightning Application Delivery Controller (“Lightning ADC”), Thunder Carrier Grade Network Address Translation (“CGN”), Thunder Threat Protection System (“TPS”), Thunder SSL Insight (“SSLi”) and Thunder Convergent Firewall (“CFW”), and two intelligent management and automation tools; Harmony Controller and aGalaxy. Our solutions are available in a variety of form factors, such as optimized hardware appliances, bare metal software, virtual appliances and cloud-native software. Basis of Presentation The accompanying unaudited condensed consolidated financial statements include those of A10 Networks, Inc. and its subsidiaries after elimination of all intercompany accounts and transactions. We have prepared the accompanying unaudited condensed consolidated financial statements pursuant to the rules and regulations of the United States Securities and Exchange Commission (the “SEC”). As permitted under these rules and regulations, we have condensed or omitted certain financial information and footnote disclosures we normally include in our annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The unaudited condensed consolidated balance sheet as of December 31, 2017 has been derived from our audited financial statements, which are included in our 2017 Annual Report on Form 10-K for the year ended December 31, 2017 on file with the SEC (our “Annual Report”). These financial statements have been prepared on the same basis as our annual financial statements and, in management’s opinion, reflect all adjustments consisting only of normal recurring adjustments that are necessary for a fair presentation of our financial information. Our interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the financial statements and accompanying notes thereto in our Annual Report. Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation in the condensed consolidated balance sheets and the condensed consolidated statements of cash flows. We have separately presented the line items “Proceeds from sales of marketable securities” and “Proceeds from maturities of marketable securities” as opposed to our historical consolidated presentation of “Proceeds from sales and maturities of marketable securities” in the condensed consolidated statement of cash flows for the nine months ended September 30, 2017 . 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, the allowance for doubtful accounts, the sales return reserve, the valuation of inventory, the fair value of marketable securities, contingencies and litigation, acquisition related purchase price allocations, accrued liabilities, deferred commissions and the 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 Company’s significant accounting policies are disclosed in its Annual Report on Form 10-K for the year ended December 31, 2017. Other than the accounting policies related to the adoption of Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) discussed in Note 11 in this report, there have been no material changes to the Company’s significant accounting policies during the nine months ended September 30, 2018 . 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 held and invested in high-credit quality financial instruments by recognized financial institutions and are subject to minimum credit risk. 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 based on a number of factors, including past transaction experience, evaluation of credit history and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent 10% or more of our total revenue for each period presented or our gross accounts receivable balance as of each respective balance sheet date. Revenues from our significant customers as a percentage of our total revenue are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Customer A (a distribution channel partner) 16% * 14% 10% Customer B (a distribution channel partner) * 11% * * Customer C (a direct customer) * 14% * 10% * represents less than 10% of total revenue As of September 30, 2018 , one customer accounted for 17% of our total gross accounts receivable. As of December 31, 2017 , no customer accounted for 10% or more of our total gross accounts receivable. Recently Adopted Accounting Guidance In May 2017, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting, to provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. This standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. The amendments will be applied prospectively to an award modified on or after the adoption date. The adoption of ASU 2017-09 on January 1, 2018 did not impact our condensed consolidated financial statements or disclosures. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as subsequently amended, which supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition. This ASU requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This ASU also includes Subtopic 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the capitalization of incremental customer acquisition costs and amortization of these costs over the contract period or estimated customer life which resulted in the recognition of a deferred commission asset on our condensed consolidated balance sheet. We adopted ASU 2014-09 and its related amendments (collectively “ASC 606”) on January 1, 2018 using the modified retrospective method. See Note 11 in this report for disclosure on the impact of adopting this standard. Recent Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued 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. In July 2018, FASB issued ASU No. 2018-11, Topic 842 - Targeted Improvements. The update requires modified retrospective transition, with the option to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment and elect various practical expedients. This standard is effective for annual periods beginning after December 15, 2018 with early adoption permitted. We will adopt this standard effective January 1, 2019. We are evaluating the impact of this guidance on our condensed consolidated financial statements and related disclosures. We expect to apply the new transition method prescribed by ASU 2018-11 at the adoption date. We expect the most prominent impact on our condensed consolidated financial statements to be the recognition of right-of-use assets and lease liabilities for those leases classified as operating leases. We expect the standard to have a material impact on our condensed consolidated balance sheets, but an immaterial impact on our condensed consolidated statement of operations. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118. These amendments add SEC guidance to the FASB Accounting Standards Codification regarding the Tax Cuts and Jobs Act pursuant to the issuance of SAB 118. The amendments are effective upon addition to the FASB Codification. See Note 9 in this report for disclosures related to the effect of the Tax Cuts and Jobs Act and our utilization of SAB 118. In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. This final rule is effective on November 5, 2018. We are evaluating the impact of this guidance on our condensed consolidated financial statements and expect to adopt this guidance in the first quarter of 2019. There are several other new accounting pronouncements issued by the FASB, which we will adopt. However, we do not believe any of those accounting pronouncements will have a material impact on our consolidated financial position, operating results or statements of cash flows.

Restatement of Previously Issue

Restatement of Previously Issued Consolidated Financial Statements	9 Months Ended
	Sep. 30, 2018
Accounting Changes and Error Corrections [Abstract]
Restatement of Previously Issued Consolidated Financial Statements	Restatement of Previously Issued Consolidated Financial Statements Restatement Background Subsequent to the issuance of the condensed consolidated financial statements as of September 30, 2017, the Audit Committee of our Board of Directors (the “Audit Committee”) commenced an investigation (the “Investigation”) with the assistance of outside counsel relating to certain accounting and internal control matters at the Company, principally focused on certain revenue recognition matters from the fourth quarter of 2015 through the fourth quarter of 2017 inclusive. The investigation was conducted with the assistance of outside counsel and independent counsel. Counsel retained forensic accountants to assist with their work. The investigation commenced following the identification of violations of the Company's Insider Trading Policy and Code of Conduct by a mid-level employee within the finance department, and as a result it was determined that further review and procedures relating to certain accounting and internal control matters should be undertaken. During the course of this Investigation, code of conduct breaches and accounting and financial reporting errors were identified. The matters primarily resulted in modification to the timing of the recognition of revenue in a limited number of sale transactions between the Company and its resellers and distributors. The Company determined the need to restate its interim condensed consolidated financial statements for each of the first three quarters of 2017, and the consolidated statements as of and for the year ended December 31, 2016, including interim periods therein. The Company also adjusted the consolidated financial statements as of and for the year ended December 31, 2015 to correct identified immaterial errors. Revenue Recognition Adjustments During the three and nine months ended September 30, 2017, revenue on certain sale transactions was recognized prematurely in prior periods, as it was determined that there was an oversight or misuse of facts which indicated that the reseller’s or distributor’s price was not fixed or determinable, or that collectibility was not reasonably assured, because the reseller’s or distributor’s payment to the Company was contingent on resale of the product or the transaction included extended payment terms beyond the Company’s customary terms. To correct these errors, the related revenue and cost of revenue were reversed in the period in which the accounting errors took place and have been recognized in subsequent periods when all of the revenue recognition criteria were met. Additionally, certain adjustments to accounts receivable, net of allowances, inventory, prepaid expenses and other assets and deferred revenue, current, were made to the condensed consolidated balance sheet at the end of the period in which the accounting errors occurred. Other Adjustments In addition to the restatement adjustments described above, we have identified other revenue and expense classification errors that are not material, individually or in the aggregate that have been corrected in connection with the restatement. Tax effect of restatement adjustments The Company recorded adjustments to its deferred taxes as a result of the restatement. The overall impact of the restatement is an increase to deferred taxes with the corresponding increase to the valuation allowance with no impact to the effective tax rate or income tax expense. Impact of the Restatement The following tables present the condensed consolidated statement of operations as previously reported, restatement adjustments and the condensed consolidated statement of operations as restated for the three and nine months ended September 30, 2017 (in thousands, except per share amounts): Three Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments Other Adjustments As Restated Revenue: Products $ 39,389 $ 517 $ 498 $ 40,404 Services 22,030 69 (498 ) 21,601 Total revenue 61,419 586 — 62,005 Cost of revenue: Products 9,119 108 130 9,357 Services 4,640 — (130 ) 4,510 Total cost of revenue 13,759 108 — 13,867 Gross profit $ 47,660 $ 478 $ — $ 48,138 Operating expenses: General and administrative $ 6,878 $ 67 $ — $ 6,945 Total operating expenses $ 49,805 $ 67 $ — $ 49,872 Loss from operations $ (2,145 ) $ 411 $ — $ (1,734 ) Loss before income taxes $ (2,202 ) $ 411 $ — $ (1,791 ) Net loss $ (2,656 ) $ 411 $ — $ (2,245 ) Net loss per share: Basic and diluted $ (0.04 ) $ (0.03 ) Weighted-average shares used in computing net loss per share: Basic and diluted 70,705 70,705 Nine Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments Other Adjustments As Restated Revenue: Products $ 111,195 $ 4,467 $ 1,268 $ 116,930 Services 64,199 51 (1,268 ) 62,982 Total revenue 175,394 4,518 — 179,912 Cost of revenue: Products 26,973 814 337 28,124 Services 13,623 — (337 ) 13,286 Total cost of revenue 40,596 814 — 41,410 Gross profit $ 134,798 $ 3,704 $ — $ 138,502 Operating expenses: General and administrative $ 21,028 $ 416 $ — $ 21,444 Total operating expenses $ 149,311 $ 416 $ — $ 149,727 Loss from operations $ (14,513 ) $ 3,288 $ — $ (11,225 ) Loss before income taxes $ (13,862 ) $ 3,288 $ — $ (10,574 ) Net loss $ (14,825 ) $ 3,288 $ — $ (11,537 ) Net loss per share: Basic and diluted $ (0.21 ) $ (0.17 ) Weighted-average shares used in computing net loss per share: Basic and diluted 69,688 69,688 The following table presents the condensed consolidated statement of cash flows as previously reported, restatement adjustments, and the condensed consolidated statement of cash flows as restated for the nine months ended September 30, 2017 (in thousands): Nine Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments As Restated Cash flows from operating activities: Net loss $ (14,825 ) $ 3,288 $ (11,537 ) Adjustments to reconcile net loss to net cash provided by operating activities: Changes in operating assets and liabilities: Accounts receivable, net $ 16,049 $ (4,761 ) $ 11,288 Inventory $ (3,242 ) $ 729 $ (2,513 ) Prepaid expenses and other assets $ (2,870 ) $ 85 $ (2,785 ) Deferred revenue $ (1,904 ) $ 659 $ (1,245 ) Net cash provided by operating activities $ 10,020 $ — $ 10,020 The only change to the condensed consolidated statement of comprehensive loss for the three and nine months ended September 30, 2017 as a result of the restatements is due to the changes in net loss. Refer to the condensed consolidated statement of comprehensive loss as restated.

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Marketable Securities and Fair Value Measurements	Marketable Securities and Fair Value Measurements Marketable Securities Marketable securities, classified as available-for-sale, consisted of the following (in thousands): September 30, 2018 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 14,999 $ 10 $ (1 ) $ 15,008 $ 17,000 $ 6 $ (1 ) $ 17,005 Corporate securities 47,419 7 (118 ) 47,308 39,154 1 (76 ) 39,079 U.S. Treasury and agency securities 3,747 — (18 ) 3,729 5,744 — (19 ) 5,725 Commercial paper 5,931 — (3 ) 5,928 9,225 1 (2 ) 9,224 Asset-backed securities 15,452 — (34 ) 15,418 13,567 — (33 ) 13,534 $ 87,548 $ 17 $ (174 ) $ 87,391 $ 84,690 $ 8 $ (131 ) $ 84,567 During the nine months ended September 30, 2018 and 2017 , we did not reclassify any amount to earnings from accumulated other comprehensive loss related to unrealized gains or losses. The following table summarizes the cost and estimated fair value of marketable securities based on stated effective maturities as of September 30, 2018 (in thousands): Amortized Cost Fair Value Less than 1 year $ 54,749 $ 54,668 Mature in 1 - 3 years 32,799 32,723 $ 87,548 $ 87,391 All available-for-sale securities have been classified as current because they are available for use in current operations. Marketable securities in an unrealized loss position consisted of the following (in thousands): Less Than 12 Months 12 Months or More Total As of September 30, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) $ — $ — $ 2,999 $ (1 ) Corporate securities 38,550 (110 ) 2,143 (8 ) 40,693 (118 ) U.S. Treasury and agency securities 1,731 (16 ) 1,998 (2 ) 3,729 (18 ) Commercial paper 4,940 (3 ) — — 4,940 (3 ) Asset-backed securities 8,463 (19 ) 5,562 (15 ) 14,025 (34 ) $ 56,683 $ (149 ) $ 9,703 $ (25 ) $ 66,386 $ (174 ) Less Than 12 Months 12 Months or More Total As of December 31, 2017 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) $ — $ — $ 2,999 $ (1 ) Corporate securities 36,079 (74 ) 1,499 (2 ) 37,578 (76 ) U.S. Treasury and agency securities 2,246 (2 ) 3,479 (17 ) 5,725 (19 ) Commercial paper 4,232 (2 ) — — 4,232 (2 ) Asset-backed securities 11,415 (32 ) 728 (1 ) 12,143 (33 ) $ 56,971 $ (111 ) $ 5,706 $ (20 ) $ 62,677 $ (131 ) Based on evaluation of securities that have been in a continuous loss position, we did not recognize any other-than-temporary impairment charges during the nine months ended September 30, 2018 and 2017 . Fair Value Measurements 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, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash $ 25,688 $ — $ — $ 25,688 $ 34,453 $ — $ — $ 34,453 Cash equivalents 10,474 — — 10,474 12,114 — — 12,114 Certificates of deposit — 15,008 — 15,008 — 17,005 — 17,005 Corporate securities — 47,308 — 47,308 — 39,079 — 39,079 U.S. Treasury and agency securities — 3,729 — 3,729 — 5,725 — 5,725 Commercial paper — 5,928 — 5,928 — 9,224 — 9,224 Asset-backed securities — 15,418 — 15,418 — 13,534 — 13,534 $ 36,162 $ 87,391 $ — $ 123,553 $ 46,567 $ 84,567 $ — $ 131,134 There were no transfers between Level 1 and Level 2 fair value measurement categories during the nine months ended September 30, 2018 and 2017 .

Condensed Consolidated Financia

Condensed Consolidated Financial Statement Details	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Condensed Consolidated Financial Statement Details	Condensed Consolidated Financial Statement Details Inventory Inventory consisted of the following (in thousands): September 30, December 31, Raw materials $ 6,118 $ 6,643 Finished goods 8,984 10,934 Total inventory $ 15,102 $ 17,577 Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): Useful Life September 30, December 31, (in years) Equipment 1-3 $ 49,930 $ 47,817 Software 1-3 4,033 3,988 Furniture and fixtures 1-3 951 950 Leasehold improvements 2-8 3,836 3,824 Construction in progress 284 — Property and equipment, gross 59,034 56,579 Less: accumulated depreciation (51,040 ) (46,666 ) Property and equipment, net $ 7,994 $ 9,913 Depreciation expense on property and equipment was $1.5 million for each of the three months ended September 30, 2018 and 2017 , and $4.9 million and $5.1 million for the nine months ended September 30, 2018 and 2017, respectively. Intangible Assets Purchased intangible assets, net, consisted of the following (in thousands): September 30, 2018 December 31, 2017 Cost Accumulated Amortization Net Cost Accumulated Amortization Net Developed technology $ 5,050 $ (2,273 ) $ 2,777 $ 5,050 $ (1,515 ) $ 3,535 Patents 2,936 (1,605 ) 1,331 2,936 (1,281 ) 1,655 Total $ 7,986 $ (3,878 ) $ 4,108 $ 7,986 $ (2,796 ) $ 5,190 Amortization expense related to purchased intangible assets was $0.4 million for each of the three months ended September 30, 2018 and 2017 , and $1.1 million for each of the nine months ended September 30, 2018 and 2017 . Purchased intangible assets will be amortized over a remaining weighted average useful life of 2.9 years. Future amortization expense for purchased intangible assets as of September 30, 2018 is as follows (in thousands): Fiscal Year Remainder of 2018 $ 361 2019 1,442 2020 1,442 2021 863 $ 4,108 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, December 31, Accrued compensation and benefits $ 12,003 $ 13,828 Accrued tax liabilities 3,632 2,985 Other 4,967 5,022 Total accrued liabilities $ 20,602 $ 21,835 Deferred Revenue Deferred revenue consisted of the following (in thousands): September 30, December 31, Deferred revenue: Products $ 5,109 $ 6,161 Services 89,746 88,476 Total deferred revenue 94,855 94,637 Less: current portion (60,653 ) (61,858 ) Non-current portion $ 34,202 $ 32,779

Credit Facility

Credit Facility	9 Months Ended
	Sep. 30, 2018
Line of Credit Facility [Abstract]
Credit Facility	Credit Facility In November 2016, we entered into a loan and security agreement (the “2016 Credit Facility”) with Silicon Valley Bank (“SVB”) as the 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 subfacility. When the balance of our cash, cash equivalents and marketable securities minus outstanding revolving loans and letters of credit equals or exceeds $50.0 million , loans may be advanced under the 2016 Credit Facility up to the full $25.0 million . When our net cash falls below $50.0 million , loans may be advanced under the 2016 Credit Facility based on a borrowing base equal to a specified percentage of the value of our eligible accounts receivable. 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. In September 2018, we entered into an amendment with SVB to reduce the unused revolving credit facility fee on the 2016 Credit Facility from 0.4% to 0.3% . 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. In addition, the 2016 Credit Facility requires us to maintain compliance with an adjusted quick ratio of not less than 1.50:1.00, as determined in accordance with the 2016 Credit Facility. As of September 30, 2018 , we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Legal Proceedings Litigation 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. Some of these proceedings involve claims that are subject to substantial uncertainties and unascertainable damages. We make a provision for a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. Unless otherwise specifically disclosed in this note, we have determined that no provision for liability nor disclosure is required related to any claim against us because: (a) there is not a reasonable possibility that a loss exceeding amounts already recognized (if any) may be incurred with respect to such claim; (b) a reasonably possible loss or range of loss cannot be estimated; or (c) such estimate is immaterial. On March 22, 2018, the Company, our Chief Executive Officer, our Chief Financial Officer, and certain former officers, were named as defendants in a putative class action lawsuit filed in the United States District Court for the Northern District of California, captioned Shah v. A10 Networks, Inc. et al., 3:18-cv-01772-VC (the “Securities Action”). On August 31, 2018, the court appointed a lead plaintiff. On October 5, 2018, the lead plaintiff filed an amended complaint. The amended complaint names the same defendants as the initial complaint, in addition to one of the Company’s former executive vice presidents. The amended complaint asserts claims under Sections 10(b) and 20(a) of the Securities Exchange Act of 1934 and Rule 10b-5 promulgated thereunder. On May 30, 2018, certain of our current and former directors and officers were named as defendants in a putative shareholder derivative lawsuit filed in the United States District Court for the Northern District of California, captioned Moulton v. Chen et al., 3:18-cv-03223-VC (the “Derivative Action”). We were also named as a nominal defendant. The complaint in the Derivative Action alleges breaches of fiduciary duties and other related claims in connection with purported misrepresentations related to internal controls and revenues and failures to ensure that financial statements were made in accordance with generally accepted accounting principles. Plaintiff seeks unspecified damages allegedly sustained by the Company, restitution, and other relief. On July 11, 2018 the Derivative Action was stayed until a motion to dismiss in the Securities Action is granted with prejudice or denied in whole or in part. Defendants are not required to move or otherwise respond to the current complaint. On October 24, 2018, the Company was sued in the Federal District Court for the Northern District of California by Firenet Technologies, LLC, which we believe is a non-practicing patent holding company. The complaint alleges infringement of certain patents purportedly owned by the plaintiff. The Company is currently evaluating the matter and intends to vigorously defend the lawsuit, but the Company is unable to reasonably estimate a possible loss or range of possible loss, if any, arising from this matter at this early stage. Accordingly, no accrued litigation expense has been recorded in the accompanying condensed consolidated financial statements. Investigations The U.S. Securities and Exchange Commission (“SEC”) is conducting a private investigation into possible violations of Section 17(a) of the Securities Act of 1933 and Sections 10(b), 13(a), and 13(b) of the Securities Exchange Act of 1934 (“Exchange Act”) and Rules 10b-5, 12b-20, 13a-1, 13a-11, 13a-13, 13a-14, 13a-15, and 13b2-1 thereunder. The Company is cooperating with the SEC regarding this investigation. The Company is unable to predict the duration, scope or outcome of the investigation, but an adverse outcome is reasonably possible. In such an event, the Company could be required to pay fines and sanctions and/or implement additional remedial measures. However, the Company is not able to estimate the likelihood or a reasonable range of possible loss. Lease 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 2022 . 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. Guarantees and Indemnifications In the normal course of business, we provide indemnifications to customers against claims of intellectual property infringement made by third parties arising from the use of our products. Other guarantees or indemnification arrangements include guarantees of product and service performance, and standby letters of credit for lease facilities and corporate credit cards. We have not recorded a liability related to these indemnification and guarantee provisions and our guarantees and indemnification arrangements have not had any significant impact on our consolidated financial statements to date.

Equity Incentive Plans and Stoc

Equity Incentive Plans and Stock-Based Compensation	9 Months Ended
	Sep. 30, 2018
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 The 2014 Equity Incentive Plan (the “2014 Plan”) provides for the granting of stock options, restricted stock awards, restricted stock units (“RSUs”), performance-based RSUs (“PSUs”), stock appreciation rights, performance units and performance shares to our employees, consultants and members of our board of directors. In June 2015, our board of directors adopted and our stockholders approved an amendment and restatement of the 2014 Plan, which increased the number of shares available for issuance under the 2014 Plan by the number of shares granted under the 2008 Stock Plan (the “2008 Plan”) that were or may in the future be canceled or otherwise forfeited or repurchased after March 20, 2014. A maximum of 8,310,566 shares may become available from such awards granted under the 2008 Plan for issuance under the 2014 Plan. The shares authorized for the 2014 Plan increase annually 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. Accordingly, on January 1, 2018 , the number of shares in the 2014 Plan increased by 3,584,623 shares, representing 5% of the prior year end’s common stock outstanding. As of September 30, 2018 , we had a total of 11,580,435 shares available for future grant. 2014 Employee Stock Purchase Plan The 2014 Employee Stock Purchase Plan (the “2014 Purchase Plan”) provides for twenty-four month offering periods with four six-month purchase periods in each offering period. Employees purchase shares in each purchase period at 85% of the market value of our common stock at the beginning of the offering period or the end of the purchase period, whichever is lower. If the market value of our common stock at the end of the purchase period is less than the market value at the beginning of the offering period, participants will be withdrawn from the then current offering period following their purchase of shares, and automatically will be enrolled in the immediately following offering period. Participants may contribute up to 15% of their eligible compensation, subject to certain limits. As of September 30, 2018 , we had 3,065,182 shares available for future issuance under the 2014 Purchase Plan. The 2014 Purchase Plan was suspended effective March 16, 2018 due to the delay of the Form 10-K filing for the fiscal year ended December 31, 2017. Accordingly, there were no stock purchases under the 2014 Purchase Plan during the three and nine months ended September 30, 2018 . In October 2018, the Board approved amending our 2014 Purchase Plan in order to, among other things, reduce the maximum contribution participants can make under the plan from 15% to 10% of eligible compensation. Our 2014 Purchase Plan as amended also reflects revised offering periods, which were changed from 24 to six months in duration and that begin on or about December 1 and June 1 each year, starting in December 2018. Stock-Based Compensation A summary of our stock-based compensation expense is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock-based compensation by type of award: Stock options $ 291 $ 589 $ 922 $ 2,199 Stock awards 2,042 2,969 6,976 9,269 Employee stock purchase rights (1) — 987 5,157 2,356 $ 2,333 $ 4,545 $ 13,055 $ 13,824 Stock-based compensation by category of expense: Cost of revenue $ 187 $ 403 $ 1,277 $ 1,068 Sales and marketing 619 1,696 4,085 5,120 Research and development 960 1,537 5,345 5,024 General and administrative 567 909 2,348 2,612 $ 2,333 $ 4,545 $ 13,055 $ 13,824 (1) Amount for the nine months ended September 30, 2018 includes $4.1 million of accelerated stock-based compensation expense. In March 2018, as a result of a suspension of the 2014 Purchase Plan due to our non-timely filing status, all unrecognized stock-based compensation expense related to ESPP was accelerated and recognized within the condensed consolidated statement of operations. As of September 30, 2018 , we had $18.4 million of unrecognized stock-based compensation expense related to unvested stock-based awards which will be recognized over a weighted-average period of 1.9 years. Stock Options The following tables summarize our stock option activities and related information: Number of Shares (thousands) Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Outstanding as of December 31, 2017 6,018 $ 5.18 Granted — $ — Exercised (359 ) $ 3.54 Canceled (1) (314 ) $ 8.84 Outstanding as of September 30, 2018 5,345 $ 5.07 4.3 $ 8,455 Vested and exercisable as of September 30, 2018 4,795 $ 4.90 3.9 $ 8,201 (1) Includes 249,491 shares of canceled stock options from the 2008 Plan that became available for issuance under the 2014 Plan. As of September 30, 2018 , the aggregate intrinsic value represents the excess of the closing price of our common stock of $6.08 over the exercise price of the outstanding in-the-money options. The intrinsic value of options exercised was $1.1 million and $7.0 million during the nine months ended September 30, 2018 and 2017 , respectively. Stock Awards We have granted RSUs to our employees, consultants and members of our board of directors, and PSUs and market performance-based restricted stock units (“MSUs”) to certain executives. In 2014 and 2015, we granted 540,000 MSUs and 40,000 MSUs, respectively, to certain executives. 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 grant date, subject to continued service by the award holder. None of these MSUs were vested as of September 30, 2018 . In February 2016, we granted 547,000 PSUs with certain financial and operational targets. Actual performance, as measured at the time and prior to the restatement of the 2016 financial statements, resulted in participants achieving 80% of target. Given the PSUs did not contain explicit or implicit claw back rights, there was no change to stock-based compensation expense for the impact of the restatement. As of September 30, 2018 , 178,402 shares had vested, 181,600 shares were forfeited, and the remaining shares will vest in annual tranches through February 2020 subject to continued service vesting requirements. In October 2016, we granted 60,641 PSUs with certain financial and operational targets. To the extent they become eligible to vest upon achievement of the performance targets, these PSUs additionally are subject to service condition vesting requirements with scheduled vesting dates of March 2017 through June 2018. As of September 30, 2018 , 30,320 shares were vested and 30,321 shares were forfeited. The following table summarizes our stock award activities and related information: Number of Shares (thousands) Weighted-Average Grant Date Fair Value Weighted-Average Remaining Vesting Term (years) Unvested as of December 31, 2017 5,568 $ 6.88 Granted 99 $ 6.86 Released (656 ) $ 6.44 Canceled (854 ) $ 7.38 Unvested as of September 30, 2018 4,157 $ 6.85 1.1 The aggregate fair value of stock awards released as of the respective vesting dates was $4.3 million and $12.2 million for the nine months ended September 30, 2018 and 2017 , respectively. In October 2018, upon the resumption of timely filings with the SEC, we resumed our equity plan activities and granted approximately 3.1 million stock awards and 0.3 million stock options to our employees. Stock Repurchase Program On October 23, 2017, our board of directors authorized a share repurchase program for up to $20.0 million of our common stock over 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. No shares were repurchased under this repurchase program as of September 30, 2018 . Our share repurchase program expired in October 2018.

Net Loss Per Share

Net Loss Per Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss Per Share Basic net loss per share is computed using the weighted average number of common shares outstanding for the period. Diluted net loss per share is computed using the weighted average number of common shares outstanding for the period plus potential dilutive common shares, including stock options, RSUs and employee stock purchase rights, unless the potential common shares are anti-dilutive. Since we had net losses in the three and nine months ended September 30, 2018 and 2017 , none of the potential dilutive common shares were included in the computation of diluted shares for these periods, as inclusion of such shares would have been anti-dilutive. The following table presents common shares related to potentially dilutive shares excluded from the calculation of diluted net loss per share as their effect would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock options, RSUs and employee stock purchase rights 8,546 10,071 9,395 12,587

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded income tax expense of $0.1 million and $0.5 million for the three months ended September 30, 2018 and 2017 , respectively, and $0.7 million and $1.0 million for the nine months ended September 30, 2018 and 2017 , 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 our deferred tax assets 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, 2018 . 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 $3.8 million of unrecognized tax benefits as of September 30, 2018 and December 31, 2017 . 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. We are subject to taxation in the United States, various states, and several foreign jurisdictions. Because we have net operating loss and credit carryforwards, there are open statutes of limitations in which federal, state and foreign taxing authorities may examine our tax returns for all years from 2004 through the current period. We are not currently under examination by any taxing authorities. The Tax Cuts and Jobs Act In December 2017, the United States enacted the Tax Cuts and Jobs Act (“TCJA”), which instituted fundamental changes to the taxation of multinational corporations, including, but not limited to: (1) a reduction of the U.S. federal corporate income tax rate to 21% for tax years beginning after December 31, 2017; (2) a requirement for companies to pay a one-time transition tax on certain unremitted earnings of foreign subsidiaries; and, (3) the transition of international taxation from a worldwide tax system to a territorial system. On December 22, 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of GAAP in situations when a registrant does not have the necessary information available, prepared or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the TCJA. For the nine months ended September 30, 2018 , the accounting for the TCJA remained incomplete, but there were no material changes to the provisional tax impacts assessed for the year ended December 31, 2017. The ultimate impact may materially differ from these provisional amounts due to, among other things, additional analysis, changes in interpretations and assumptions the Company has made, additional regulatory guidance that may be issued, and actions the Company may take as a result of the TCJA. The accounting is expected to be completed when the 2017 U.S. corporate income tax return is filed in 2018.

Geographic Information

Geographic Information	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Geographic Information	Geographic Information The following table depicts the disaggregation of revenue by geographic region based on the ship to location of our customers and is consistent with how we evaluate our financial performance (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 United States $ 27,003 $ 28,951 $ 78,124 $ 92,140 Japan 14,023 16,634 38,971 38,119 Asia Pacific, excluding Japan 9,331 7,171 27,436 25,594 EMEA 8,119 6,117 20,038 18,535 Other 2,026 3,132 5,829 5,524 $ 60,502 $ 62,005 $ 170,398 $ 179,912 The following table is a summary of our long-lived assets which include property and equipment, net based on the physical location of the assets (in thousands): September 30, December 31, United States $ 6,080 $ 7,733 Japan 1,210 1,510 Other 704 670 Total $ 7,994 $ 9,913

Revenue Revenue

Revenue Revenue	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue ASC 606 Adoption Impact On January 1, 2018, we adopted ASC 606 applying the modified retrospective method. We recognized the cumulative effect of initially applying the new guidance as an adjustment to the opening balance of accumulated deficit as of the adoption date. We applied ASC 606 to all contracts that were not completed at the date of initial application. Comparative information for prior periods has not been restated and continues to be reported under the accounting standards in effect for those periods. In connection with the adoption of ASC 606, we also adopted ASC 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the deferral of incremental costs of obtaining a contract with a customer. Collectively, we refer to ASC 606 and ASC 340-40 as the “new standard.” Adoption of the new standard resulted in changes to our accounting policies for revenue recognition, commissions and deferred commissions as discussed below. We recorded a reduction to opening accumulated deficit of $12.4 million as of January 1, 2018 due to the cumulative impact of adopting the new standard as follows: • A decrease in total deferred revenue of $4.0 million primarily due to the removal of the current limitation on contingent revenue that would have accelerated revenue recognition for certain of our historical revenue contracts; and • Recognition of a deferred commissions asset of $8.4 million due to the requirement under the new standard to recognize incremental customer acquisition costs in our condensed consolidated statement of operations as the related performance obligations are met as compared to the previous recognition to expense as incurred. Impact on the Condensed Consolidated Financial Statements The following tables summarize the impact of the new standard on our condensed consolidated statement of balance sheet and condensed consolidated of operations for the period presented: Selected Condensed Consolidated Balance Sheet Line Items September 30, 2018 (in thousands) As Reported Adjustments Balance Without Adopting the New Standard Assets Prepaid expenses and other current assets $ 13,266 $ (5,824 ) $ 7,442 Other non-current assets 8,380 (3,000 ) 5,380 Liabilities Deferred revenue, current 60,653 3,164 63,817 Deferred revenue, non-current 34,202 2,220 36,422 Stockholders' Equity Accumulated deficit (270,637 ) (14,208 ) (284,845 ) Selected Condensed Consolidated Statement of Operations Line Items Three Months Ended September 30, 2018 (in thousands, except per share amounts) As Reported Adjustments Balance Without Adopting the New Standard Revenue - products $ 38,265 $ (475 ) $ 37,790 Revenue - services 22,237 — 22,237 Total revenue 60,502 (475 ) 60,027 Gross profit 47,488 (475 ) 47,013 Sales and marketing 24,539 292 24,831 Total operating expenses 49,056 292 49,348 Loss from operations (1,568 ) (767 ) (2,335 ) Net loss (1,807 ) (767 ) (2,574 ) Basic and diluted net loss per share (0.02 ) (0.04 ) Nine Months Ended September 30, 2018 (in thousands, except per share amounts) As Reported Adjustments Balance Without Adopting the New Standard Revenue - products $ 105,638 $ (1,384 ) $ 104,254 Revenue - services 64,760 — 64,760 Total revenue 170,398 (1,384 ) 169,014 Gross profit 132,313 (1,384 ) 130,929 Sales and marketing 77,231 420 77,651 Total operating expenses 157,569 420 157,989 Loss from operations (25,256 ) (1,804 ) (27,060 ) Net loss (26,009 ) (1,804 ) (27,813 ) Basic and diluted net loss per share (0.36 ) (0.38 ) Changes in Accounting Policies Revenue Recognition We derive revenue from two sources: (i) products revenue, which includes hardware, perpetual software license and subscription revenue; and (ii) services revenue, which includes post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those products or services. We apply the following five-step revenue recognition model: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, performance obligations are satisfied. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years as there is no discernable pattern of transfer related to these promises. Billed but unearned PCS revenue is included in deferred revenue. Professional service revenue primarily consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Revenue is recognized for training when the training course is delivered. Contracts with Multiple Performance Obligations Most of our contracts with customers, other than renewals of PCS, contain multiple performance obligations with a combination of products and PCS. Products and PCS generally qualify as distinct performance obligations. Our hardware includes embedded ACOS software, which together deliver the essential functionality of our products. For contracts which contain multiple performance obligations, we allocate revenue to each distinct performance obligation based on the standalone selling price (“SSP”). Judgment is required to determine the SSP for each distinct performance obligation. We use a range of amounts to estimate SSP for products and PCS sold together in a contract to determine whether there is a discount to be allocated based on the relative SSP of the various products and PCS. If we do not have an observable SSP, such as when we do not sell a product or service separately, then SSP is estimated using judgment and considering all reasonably available information such as market conditions and information about the size and/or purchase volume of the customer. We generally use a range of amounts to estimate SSP for individual products and services based on multiple factors including, but not limited to the sales channel (reseller, distributor or end customer), the geographies in which our products and services are sold, and the size of the end customer. We account for multiple contracts with a single partner as one arrangement if the contractual terms and/or substance of those agreements indicate that they may be so closely related that they are, in effect, parts of a single contract. We may occasionally accept returns to address customer satisfaction issues even though there is generally no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period shipments. Specific customer returns and allowances are considered when determining our sales return reserve estimate. Our policy applies to the accounting for individual contracts. However, we have elected a practical expedient to apply the guidance to a portfolio of contracts or performance obligations with similar characteristics so long as such application would not differ materially from applying the guidance to the individual contracts (or performance obligations) within that portfolio. Consequently, we have chosen to apply the portfolio approach when possible, which we do not believe will happen frequently. Additionally, we will evaluate a portfolio of data, when possible, in various situations, including accounting for commissions, rights of return and transactions with variable consideration. We report revenue net of sales taxes. We include shipping charges billed to customers in revenue and the related shipping costs are included in cost of product revenue. Contract Balances The following table reflects contract balances with customers (in thousands): As of As of Adoption Balance Sheet Line Reference September 30, 2018 January 1, 2018 Accounts receivable, net Accounts receivables, net $ 51,084 $ 48,266 Deferred revenue, current Deferred revenue 60,653 59,360 Deferred revenue, non-current Deferred revenue, non-current 34,202 31,276 We receive payments from customers based upon billing cycles. Invoice payment terms are usually ranging from 30 to 90 days. Accounts receivable are recorded when the right to consideration becomes unconditional. Contract assets include amounts related to our contractual right to consideration for performance obligations not yet billed and are included in prepaid and other current assets in the condensed consolidated balance sheets. The amount is immaterial as of September 30, 2018 and as of the adoption date. Deferred revenue primarily consists of amounts that have been invoiced but not yet been recognized as revenue and consists of performance obligations pertaining to support and subscription services. During the three and nine months ended September 30, 2018 , we recognized revenue of $13.2 million and $49.9 million , respectively, related to deferred revenues at the beginning of the period. Deferred Contract Acquisition Costs In connection with the adoption of ASC 340-40, we capitalize certain contract acquisition costs consisting of incremental sales commissions incurred to obtain customer contracts. Deferred commissions related to product revenues are recognized upon transfer of control to customers. Deferred commissions related to services revenue are recognized as the related performance obligations are met. Deferred commissions that will be recognized during the succeeding 12-month period are recorded as prepaid expenses and other current assets, and the remaining portion is recorded as other non-current assets. Amortization of deferred commissions is included in sales and marketing expense. Deferred contract acquisition costs were $8.8 million as of September 30, 2018 , and the related amortization amount was $1.1 million for the three months ended September 30, 2018 and $4.1 million for the nine months ended September 30, 2018 . We had no impairment loss in relation to the costs capitalized and no asset impairment charges related to contract assets. Remaining Performance Obligations Remaining performance obligations represent contracted revenues that are non-cancellable and have not yet been recognized due to unsatisfied or partially satisfied performance obligations, which includes deferred revenues and amounts that will be invoiced and recognized as revenues in future periods. We expect to recognize revenue on the remaining performance obligations as follows (in thousands): September 30, 2018 Within 1 year $ 60,653 Next 2 to 3 years 28,350 Thereafter 5,852 Total $ 94,855

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements include those of A10 Networks, Inc. and its subsidiaries after elimination of all intercompany accounts and transactions. We have prepared the accompanying unaudited condensed consolidated financial statements pursuant to the rules and regulations of the United States Securities and Exchange Commission (the “SEC”). As permitted under these rules and regulations, we have condensed or omitted certain financial information and footnote disclosures we normally include in our annual consolidated financial statements prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The unaudited condensed consolidated balance sheet as of December 31, 2017 has been derived from our audited financial statements, which are included in our 2017 Annual Report on Form 10-K for the year ended December 31, 2017 on file with the SEC (our “Annual Report”). These financial statements have been prepared on the same basis as our annual financial statements and, in management’s opinion, reflect all adjustments consisting only of normal recurring adjustments that are necessary for a fair presentation of our financial information. Our interim period operating results do not necessarily indicate the results that may be expected for any other interim period or for the full fiscal year. These financial statements and accompanying notes should be read in conjunction with the financial statements and accompanying notes thereto in our Annual Report.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation in the condensed consolidated balance sheets and the condensed consolidated statements of cash flows. We have separately presented the line items “Proceeds from sales of marketable securities” and “Proceeds from maturities of marketable securities” as opposed to our historical consolidated presentation of “Proceeds from sales and maturities of marketable securities” in the condensed consolidated statement of cash flows for the nine months ended September 30, 2017 .
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, the allowance for doubtful accounts, the sales return reserve, the valuation of inventory, the fair value of marketable securities, contingencies and litigation, acquisition related purchase price allocations, accrued liabilities, deferred commissions and the 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.
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 held and invested in high-credit quality financial instruments by recognized financial institutions and are subject to minimum credit risk. 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 based on a number of factors, including past transaction experience, evaluation of credit history and review of the invoicing terms of the contract. We generally do not require our customers to provide collateral to support accounts receivable. Significant customers, including distribution channel partners and direct customers, are those which represent 10% or more of our total revenue for each period presented or our gross accounts receivable balance as of each respective balance sheet date.
Recently Adopted Accounting Guidance/Recent Accounting Pronouncements Not Yet Effective	Recently Adopted Accounting Guidance In May 2017, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting, to provide guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting. This standard is effective for annual periods beginning after December 15, 2017 and interim periods within that reporting period. The amendments will be applied prospectively to an award modified on or after the adoption date. The adoption of ASU 2017-09 on January 1, 2018 did not impact our condensed consolidated financial statements or disclosures. In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606), as subsequently amended, which supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) Topic 605, Revenue Recognition. This ASU requires an entity to recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. This ASU also includes Subtopic 340-40, Other Assets and Deferred Costs - Contracts with Customers, which requires the capitalization of incremental customer acquisition costs and amortization of these costs over the contract period or estimated customer life which resulted in the recognition of a deferred commission asset on our condensed consolidated balance sheet. We adopted ASU 2014-09 and its related amendments (collectively “ASC 606”) on January 1, 2018 using the modified retrospective method. See Note 11 in this report for disclosure on the impact of adopting this standard. Recent Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued 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. In July 2018, FASB issued ASU No. 2018-11, Topic 842 - Targeted Improvements. The update requires modified retrospective transition, with the option to initially apply the new standard at the adoption date and recognize a cumulative-effect adjustment and elect various practical expedients. This standard is effective for annual periods beginning after December 15, 2018 with early adoption permitted. We will adopt this standard effective January 1, 2019. We are evaluating the impact of this guidance on our condensed consolidated financial statements and related disclosures. We expect to apply the new transition method prescribed by ASU 2018-11 at the adoption date. We expect the most prominent impact on our condensed consolidated financial statements to be the recognition of right-of-use assets and lease liabilities for those leases classified as operating leases. We expect the standard to have a material impact on our condensed consolidated balance sheets, but an immaterial impact on our condensed consolidated statement of operations. In March 2018, the FASB issued ASU No. 2018-05, Income Taxes (Topic 740): Amendments to SEC Paragraphs Pursuant to SEC Staff Accounting Bulletin (SAB) No. 118. These amendments add SEC guidance to the FASB Accounting Standards Codification regarding the Tax Cuts and Jobs Act pursuant to the issuance of SAB 118. The amendments are effective upon addition to the FASB Codification. See Note 9 in this report for disclosures related to the effect of the Tax Cuts and Jobs Act and our utilization of SAB 118. In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, Disclosure Update and Simplification, amending certain disclosure requirements that were redundant, duplicative, overlapping, outdated or superseded. In addition, the amendments expanded the disclosure requirements on the analysis of stockholders' equity for interim financial statements. Under the amendments, an analysis of changes in each caption of stockholders' equity presented in the balance sheet must be provided in a note or separate statement. The analysis should present a reconciliation of the beginning balance to the ending balance of each period for which a statement of comprehensive income is required to be filed. This final rule is effective on November 5, 2018. We are evaluating the impact of this guidance on our condensed consolidated financial statements and expect to adopt this guidance in the first quarter of 2019. There are several other new accounting pronouncements issued by the FASB, which we will adopt. However, we do not believe any of those accounting pronouncements will have a material impact on our consolidated financial position, operating results or statements of cash flows.
Revenue Recognition	Revenue Recognition We derive revenue from two sources: (i) products revenue, which includes hardware, perpetual software license and subscription revenue; and (ii) services revenue, which includes post contract support (“PCS”), professional services, and training. A substantial portion of our revenue is from sales of our products and services through distribution channel partners, such as resellers and distributors. Revenue is recognized, net of applicable taxes, upon transfer of control of promised products or services to customers in an amount that reflects the consideration we expect to be entitled to receive in exchange for those products or services. We apply the following five-step revenue recognition model: • Identification of the contract, or contracts, with a customer • Identification of the performance obligations in the contract • Determination of the transaction price • Allocation of the transaction price to the performance obligations in the contract • Recognition of revenue when, or as, performance obligations are satisfied. PCS revenue includes arrangements for software support and technical support for our products. PCS is offered under renewable, fee-based contracts, which include technical support, hardware repair and replacement parts, bug fixes, patches, and unspecified upgrades on a when-and-if available basis. Revenue for PCS services is recognized on a straight-line basis over the service contract term, which is typically one year, but can be up to five years as there is no discernable pattern of transfer related to these promises. Billed but unearned PCS revenue is included in deferred revenue. Professional service revenue primarily consists of the fees we earn related to installation and consulting services. We recognize revenue from professional services upon delivery or completion of performance. Professional service arrangements are typically short term in nature and are largely completed within 30 to 90 days from the start of service. Revenue is recognized for training when the training course is delivered. Contracts with Multiple Performance Obligations Most of our contracts with customers, other than renewals of PCS, contain multiple performance obligations with a combination of products and PCS. Products and PCS generally qualify as distinct performance obligations. Our hardware includes embedded ACOS software, which together deliver the essential functionality of our products. For contracts which contain multiple performance obligations, we allocate revenue to each distinct performance obligation based on the standalone selling price (“SSP”). Judgment is required to determine the SSP for each distinct performance obligation. We use a range of amounts to estimate SSP for products and PCS sold together in a contract to determine whether there is a discount to be allocated based on the relative SSP of the various products and PCS. If we do not have an observable SSP, such as when we do not sell a product or service separately, then SSP is estimated using judgment and considering all reasonably available information such as market conditions and information about the size and/or purchase volume of the customer. We generally use a range of amounts to estimate SSP for individual products and services based on multiple factors including, but not limited to the sales channel (reseller, distributor or end customer), the geographies in which our products and services are sold, and the size of the end customer. We account for multiple contracts with a single partner as one arrangement if the contractual terms and/or substance of those agreements indicate that they may be so closely related that they are, in effect, parts of a single contract. We may occasionally accept returns to address customer satisfaction issues even though there is generally no contractual provision for such returns. We estimate returns for sales to customers based on historical returns rates applied against current-period shipments. Specific customer returns and allowances are considered when determining our sales return reserve estimate. Our policy applies to the accounting for individual contracts. However, we have elected a practical expedient to apply the guidance to a portfolio of contracts or performance obligations with similar characteristics so long as such application would not differ materially from applying the guidance to the individual contracts (or performance obligations) within that portfolio. Consequently, we have chosen to apply the portfolio approach when possible, which we do not believe will happen frequently. Additionally, we will evaluate a portfolio of data, when possible, in various situations, including accounting for commissions, rights of return and transactions with variable consideration. We report revenue net of sales taxes. We include shipping charges billed to customers in revenue and the related shipping costs are included in cost of product revenue.
Deferred Contract Acquisition Costs	In connection with the adoption of ASC 340-40, we capitalize certain contract acquisition costs consisting of incremental sales commissions incurred to obtain customer contracts. Deferred commissions related to product revenues are recognized upon transfer of control to customers. Deferred commissions related to services revenue are recognized as the related performance obligations are met. Deferred commissions that will be recognized during the succeeding 12-month period are recorded as prepaid expenses and other current assets, and the remaining portion is recorded as other non-current assets. Amortization of deferred commissions is included in sales and marketing expense.

Description of Business and S_3

Description of Business and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Revenue as Percentage of Total Revenue	Revenues from our significant customers as a percentage of our total revenue are as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Customer A (a distribution channel partner) 16% * 14% 10% Customer B (a distribution channel partner) * 11% * * Customer C (a direct customer) * 14% * 10% * represents less than 10% of total revenue

Restatement of Previously Iss_2

Restatement of Previously Issued Consolidated Financial Statements (Tables)	9 Months Ended
	Sep. 30, 2018
Accounting Changes and Error Corrections [Abstract]
Schedule of Error Corrections and Prior Period Adjustments	The following table presents the condensed consolidated statement of cash flows as previously reported, restatement adjustments, and the condensed consolidated statement of cash flows as restated for the nine months ended September 30, 2017 (in thousands): Nine Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments As Restated Cash flows from operating activities: Net loss $ (14,825 ) $ 3,288 $ (11,537 ) Adjustments to reconcile net loss to net cash provided by operating activities: Changes in operating assets and liabilities: Accounts receivable, net $ 16,049 $ (4,761 ) $ 11,288 Inventory $ (3,242 ) $ 729 $ (2,513 ) Prepaid expenses and other assets $ (2,870 ) $ 85 $ (2,785 ) Deferred revenue $ (1,904 ) $ 659 $ (1,245 ) Net cash provided by operating activities $ 10,020 $ — $ 10,020 The following tables present the condensed consolidated statement of operations as previously reported, restatement adjustments and the condensed consolidated statement of operations as restated for the three and nine months ended September 30, 2017 (in thousands, except per share amounts): Three Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments Other Adjustments As Restated Revenue: Products $ 39,389 $ 517 $ 498 $ 40,404 Services 22,030 69 (498 ) 21,601 Total revenue 61,419 586 — 62,005 Cost of revenue: Products 9,119 108 130 9,357 Services 4,640 — (130 ) 4,510 Total cost of revenue 13,759 108 — 13,867 Gross profit $ 47,660 $ 478 $ — $ 48,138 Operating expenses: General and administrative $ 6,878 $ 67 $ — $ 6,945 Total operating expenses $ 49,805 $ 67 $ — $ 49,872 Loss from operations $ (2,145 ) $ 411 $ — $ (1,734 ) Loss before income taxes $ (2,202 ) $ 411 $ — $ (1,791 ) Net loss $ (2,656 ) $ 411 $ — $ (2,245 ) Net loss per share: Basic and diluted $ (0.04 ) $ (0.03 ) Weighted-average shares used in computing net loss per share: Basic and diluted 70,705 70,705 Nine Months Ended September 30, 2017 As Previously Reported Revenue Recognition Adjustments Other Adjustments As Restated Revenue: Products $ 111,195 $ 4,467 $ 1,268 $ 116,930 Services 64,199 51 (1,268 ) 62,982 Total revenue 175,394 4,518 — 179,912 Cost of revenue: Products 26,973 814 337 28,124 Services 13,623 — (337 ) 13,286 Total cost of revenue 40,596 814 — 41,410 Gross profit $ 134,798 $ 3,704 $ — $ 138,502 Operating expenses: General and administrative $ 21,028 $ 416 $ — $ 21,444 Total operating expenses $ 149,311 $ 416 $ — $ 149,727 Loss from operations $ (14,513 ) $ 3,288 $ — $ (11,225 ) Loss before income taxes $ (13,862 ) $ 3,288 $ — $ (10,574 ) Net loss $ (14,825 ) $ 3,288 $ — $ (11,537 ) Net loss per share: Basic and diluted $ (0.21 ) $ (0.17 ) Weighted-average shares used in computing net loss per share: Basic and diluted 69,688 69,688

Marketable Securities and Fai_2

Marketable Securities and Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
Fair Value Disclosures [Abstract]
Available-for-sale Securities	Marketable securities, classified as available-for-sale, consisted of the following (in thousands): September 30, 2018 December 31, 2017 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 14,999 $ 10 $ (1 ) $ 15,008 $ 17,000 $ 6 $ (1 ) $ 17,005 Corporate securities 47,419 7 (118 ) 47,308 39,154 1 (76 ) 39,079 U.S. Treasury and agency securities 3,747 — (18 ) 3,729 5,744 — (19 ) 5,725 Commercial paper 5,931 — (3 ) 5,928 9,225 1 (2 ) 9,224 Asset-backed securities 15,452 — (34 ) 15,418 13,567 — (33 ) 13,534 $ 87,548 $ 17 $ (174 ) $ 87,391 $ 84,690 $ 8 $ (131 ) $ 84,567
Schedule of Cost and Estimated Fair Values of Available-for-sale Securities by Contractual Maturity	The following table summarizes the cost and estimated fair value of marketable securities based on stated effective maturities as of September 30, 2018 (in thousands): Amortized Cost Fair Value Less than 1 year $ 54,749 $ 54,668 Mature in 1 - 3 years 32,799 32,723 $ 87,548 $ 87,391
Schedule of gross unrealized losses	Marketable securities in an unrealized loss position consisted of the following (in thousands): Less Than 12 Months 12 Months or More Total As of September 30, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) $ — $ — $ 2,999 $ (1 ) Corporate securities 38,550 (110 ) 2,143 (8 ) 40,693 (118 ) U.S. Treasury and agency securities 1,731 (16 ) 1,998 (2 ) 3,729 (18 ) Commercial paper 4,940 (3 ) — — 4,940 (3 ) Asset-backed securities 8,463 (19 ) 5,562 (15 ) 14,025 (34 ) $ 56,683 $ (149 ) $ 9,703 $ (25 ) $ 66,386 $ (174 ) Less Than 12 Months 12 Months or More Total As of December 31, 2017 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,999 $ (1 ) $ — $ — $ 2,999 $ (1 ) Corporate securities 36,079 (74 ) 1,499 (2 ) 37,578 (76 ) U.S. Treasury and agency securities 2,246 (2 ) 3,479 (17 ) 5,725 (19 ) Commercial paper 4,232 (2 ) — — 4,232 (2 ) Asset-backed securities 11,415 (32 ) 728 (1 ) 12,143 (33 ) $ 56,971 $ (111 ) $ 5,706 $ (20 ) $ 62,677 $ (131 )
Schedule of Cash, Cash Equivalents and Available-for-sale Investments Measured at Fair Value 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, 2018 December 31, 2017 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash $ 25,688 $ — $ — $ 25,688 $ 34,453 $ — $ — $ 34,453 Cash equivalents 10,474 — — 10,474 12,114 — — 12,114 Certificates of deposit — 15,008 — 15,008 — 17,005 — 17,005 Corporate securities — 47,308 — 47,308 — 39,079 — 39,079 U.S. Treasury and agency securities — 3,729 — 3,729 — 5,725 — 5,725 Commercial paper — 5,928 — 5,928 — 9,224 — 9,224 Asset-backed securities — 15,418 — 15,418 — 13,534 — 13,534 $ 36,162 $ 87,391 $ — $ 123,553 $ 46,567 $ 84,567 $ — $ 131,134

Condensed Consolidated Financ_2

Condensed Consolidated Financial Statement Details (Tables)	9 Months Ended
	Sep. 30, 2018
Property, Plant and Equipment [Abstract]
Schedule of Inventory	Inventory consisted of the following (in thousands): September 30, December 31, Raw materials $ 6,118 $ 6,643 Finished goods 8,984 10,934 Total inventory $ 15,102 $ 17,577
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): Useful Life September 30, December 31, (in years) Equipment 1-3 $ 49,930 $ 47,817 Software 1-3 4,033 3,988 Furniture and fixtures 1-3 951 950 Leasehold improvements 2-8 3,836 3,824 Construction in progress 284 — Property and equipment, gross 59,034 56,579 Less: accumulated depreciation (51,040 ) (46,666 ) Property and equipment, net $ 7,994 $ 9,913
Schedule of Acquired Intangible Assets	Purchased intangible assets, net, consisted of the following (in thousands): September 30, 2018 December 31, 2017 Cost Accumulated Amortization Net Cost Accumulated Amortization Net Developed technology $ 5,050 $ (2,273 ) $ 2,777 $ 5,050 $ (1,515 ) $ 3,535 Patents 2,936 (1,605 ) 1,331 2,936 (1,281 ) 1,655 Total $ 7,986 $ (3,878 ) $ 4,108 $ 7,986 $ (2,796 ) $ 5,190
Schedule of Future Amortization Expense for Purchased Finite-lived Intangible Assets	Future amortization expense for purchased intangible assets as of September 30, 2018 is as follows (in thousands): Fiscal Year Remainder of 2018 $ 361 2019 1,442 2020 1,442 2021 863 $ 4,108
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, December 31, Accrued compensation and benefits $ 12,003 $ 13,828 Accrued tax liabilities 3,632 2,985 Other 4,967 5,022 Total accrued liabilities $ 20,602 $ 21,835
Schedule of Deferred Revenue	Deferred revenue consisted of the following (in thousands): September 30, December 31, Deferred revenue: Products $ 5,109 $ 6,161 Services 89,746 88,476 Total deferred revenue 94,855 94,637 Less: current portion (60,653 ) (61,858 ) Non-current portion $ 34,202 $ 32,779

Equity Incentive Plans and St_2

Equity Incentive Plans and Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-based Compensation	A summary of our stock-based compensation expense is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock-based compensation by type of award: Stock options $ 291 $ 589 $ 922 $ 2,199 Stock awards 2,042 2,969 6,976 9,269 Employee stock purchase rights (1) — 987 5,157 2,356 $ 2,333 $ 4,545 $ 13,055 $ 13,824 Stock-based compensation by category of expense: Cost of revenue $ 187 $ 403 $ 1,277 $ 1,068 Sales and marketing 619 1,696 4,085 5,120 Research and development 960 1,537 5,345 5,024 General and administrative 567 909 2,348 2,612 $ 2,333 $ 4,545 $ 13,055 $ 13,824 (1) Amount for the nine months ended September 30, 2018 includes $4.1 million of accelerated stock-based compensation expense. In March 2018, as a result of a suspension of the 2014 Purchase Plan due to our non-timely filing status, all unrecognized stock-based compensation expense related to ESPP was accelerated and recognized within the condensed consolidated statement of operations.
Summary of Activity under Stock Option Plans	The following tables summarize our stock option activities and related information: Number of Shares (thousands) Weighted-Average Exercise Price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (thousands) Outstanding as of December 31, 2017 6,018 $ 5.18 Granted — $ — Exercised (359 ) $ 3.54 Canceled (1) (314 ) $ 8.84 Outstanding as of September 30, 2018 5,345 $ 5.07 4.3 $ 8,455 Vested and exercisable as of September 30, 2018 4,795 $ 4.90 3.9 $ 8,201 (1) Includes 249,491 shares of canceled stock options from the 2008 Plan that became available for issuance under the 2014 Plan.
Summary of Restricted Stock Units Activity	The following table summarizes our stock award activities and related information: Number of Shares (thousands) Weighted-Average Grant Date Fair Value Weighted-Average Remaining Vesting Term (years) Unvested as of December 31, 2017 5,568 $ 6.88 Granted 99 $ 6.86 Released (656 ) $ 6.44 Canceled (854 ) $ 7.38 Unvested as of September 30, 2018 4,157 $ 6.85 1.1

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Summary of Anti-dilutive Shares	The following table presents common shares related to potentially dilutive shares excluded from the calculation of diluted net loss per share as their effect would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Stock options, RSUs and employee stock purchase rights 8,546 10,071 9,395 12,587

Geographic Information (Tables)

Geographic Information (Tables)	9 Months Ended
	Sep. 30, 2018
Segment Reporting [Abstract]
Schedule of Total Revenue Based on Customer's Location	The following table depicts the disaggregation of revenue by geographic region based on the ship to location of our customers and is consistent with how we evaluate our financial performance (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 United States $ 27,003 $ 28,951 $ 78,124 $ 92,140 Japan 14,023 16,634 38,971 38,119 Asia Pacific, excluding Japan 9,331 7,171 27,436 25,594 EMEA 8,119 6,117 20,038 18,535 Other 2,026 3,132 5,829 5,524 $ 60,502 $ 62,005 $ 170,398 $ 179,912
Long-lived Assets by Geographic Areas	The following table is a summary of our long-lived assets which include property and equipment, net based on the physical location of the assets (in thousands): September 30, December 31, United States $ 6,080 $ 7,733 Japan 1,210 1,510 Other 704 670 Total $ 7,994 $ 9,913

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2018
Revenue from Contract with Customer [Abstract]
Schedule of New Accounting Pronouncements and Changes in Accounting Principles	Selected Condensed Consolidated Balance Sheet Line Items September 30, 2018 (in thousands) As Reported Adjustments Balance Without Adopting the New Standard Assets Prepaid expenses and other current assets $ 13,266 $ (5,824 ) $ 7,442 Other non-current assets 8,380 (3,000 ) 5,380 Liabilities Deferred revenue, current 60,653 3,164 63,817 Deferred revenue, non-current 34,202 2,220 36,422 Stockholders' Equity Accumulated deficit (270,637 ) (14,208 ) (284,845 ) Selected Condensed Consolidated Statement of Operations Line Items Three Months Ended September 30, 2018 (in thousands, except per share amounts) As Reported Adjustments Balance Without Adopting the New Standard Revenue - products $ 38,265 $ (475 ) $ 37,790 Revenue - services 22,237 — 22,237 Total revenue 60,502 (475 ) 60,027 Gross profit 47,488 (475 ) 47,013 Sales and marketing 24,539 292 24,831 Total operating expenses 49,056 292 49,348 Loss from operations (1,568 ) (767 ) (2,335 ) Net loss (1,807 ) (767 ) (2,574 ) Basic and diluted net loss per share (0.02 ) (0.04 ) Nine Months Ended September 30, 2018 (in thousands, except per share amounts) As Reported Adjustments Balance Without Adopting the New Standard Revenue - products $ 105,638 $ (1,384 ) $ 104,254 Revenue - services 64,760 — 64,760 Total revenue 170,398 (1,384 ) 169,014 Gross profit 132,313 (1,384 ) 130,929 Sales and marketing 77,231 420 77,651 Total operating expenses 157,569 420 157,989 Loss from operations (25,256 ) (1,804 ) (27,060 ) Net loss (26,009 ) (1,804 ) (27,813 ) Basic and diluted net loss per share (0.36 ) (0.38 )
Contract with Customer, Asset and Liability	The following table reflects contract balances with customers (in thousands): As of As of Adoption Balance Sheet Line Reference September 30, 2018 January 1, 2018 Accounts receivable, net Accounts receivables, net $ 51,084 $ 48,266 Deferred revenue, current Deferred revenue 60,653 59,360 Deferred revenue, non-current Deferred revenue, non-current 34,202 31,276
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	We expect to recognize revenue on the remaining performance obligations as follows (in thousands): September 30, 2018 Within 1 year $ 60,653 Next 2 to 3 years 28,350 Thereafter 5,852 Total $ 94,855

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details)	9 Months Ended
	Sep. 30, 2018toolsolution
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of software based advanced solutions | solution	6
Number of intelligent management and automation tools | tool	2

Description of Business and S_5

Description of Business and Summary of Significant Accounting Policies - Concentration Risk (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accounts Receivable
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)			17.00%
Customer A | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)	16.00%		14.00%	10.00%
Customer B | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)		11.00%
Customer C | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)		14.00%		10.00%

Restatement of Previously Iss_3

Restatement of Previously Issued Consolidated Financial Statements - Income Statement (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Total revenue	$ 60,502	$ 62,005	$ 170,398	$ 179,912
Cost of revenue:
Total cost of revenue	13,014	13,867	38,085	41,410
Gross profit	47,488	48,138	132,313	138,502
Operating expenses:
General and administrative	9,012	6,945	30,464	21,444
Total operating expenses	49,056	49,872	157,569	149,727
Loss from operations	(1,568)	(1,734)	(25,256)	(11,225)
Loss before income taxes	(1,733)	(1,791)	(25,349)	(10,574)
Net loss	$ (1,807)	$ (2,245)	$ (26,009)	$ (11,537)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.02)	$ (0.03)	$ (0.36)	$ (0.17)
Weighted-average shares used in computing net loss per share:
Basic and diluted (in shares)	72,707	70,705	72,550	69,688
As Previously Reported
Revenue:
Total revenue		$ 61,419		$ 175,394
Cost of revenue:
Total cost of revenue		13,759		40,596
Gross profit		47,660		134,798
Operating expenses:
General and administrative		6,878		21,028
Total operating expenses		49,805		149,311
Loss from operations		(2,145)		(14,513)
Loss before income taxes		(2,202)		(13,862)
Net loss		$ (2,656)		$ (14,825)
Net loss per share:
Basic and diluted (in dollars per share)		$ (0.04)		$ (0.21)
Weighted-average shares used in computing net loss per share:
Basic and diluted (in shares)		70,705		69,688
Revenue Recognition Adjustments
Revenue:
Total revenue		$ 586		$ 4,518
Cost of revenue:
Total cost of revenue		108		814
Gross profit		478		3,704
Operating expenses:
General and administrative		67		416
Total operating expenses		67		416
Loss from operations		411		3,288
Loss before income taxes		411		3,288
Net loss		411		3,288
Other Adjustments
Revenue:
Total revenue		0		0
Cost of revenue:
Total cost of revenue		0		0
Gross profit		0		0
Operating expenses:
General and administrative		0		0
Total operating expenses		0		0
Loss from operations		0		0
Loss before income taxes		0		0
Net loss		0		0
Products
Revenue:
Total revenue	$ 38,265	40,404	$ 105,638	116,930
Cost of revenue:
Total cost of revenue	8,790	9,357	24,979	28,124
Products | As Previously Reported
Revenue:
Total revenue		39,389		111,195
Cost of revenue:
Total cost of revenue		9,119		26,973
Products | Revenue Recognition Adjustments
Revenue:
Total revenue		517		4,467
Cost of revenue:
Total cost of revenue		108		814
Products | Other Adjustments
Revenue:
Total revenue		498		1,268
Cost of revenue:
Total cost of revenue		130		337
Services
Revenue:
Total revenue	22,237	21,601	64,760	62,982
Cost of revenue:
Total cost of revenue	$ 4,224	4,510	$ 13,106	13,286
Services | As Previously Reported
Revenue:
Total revenue		22,030		64,199
Cost of revenue:
Total cost of revenue		4,640		13,623
Services | Revenue Recognition Adjustments
Revenue:
Total revenue		69		51
Cost of revenue:
Total cost of revenue		0		0
Services | Other Adjustments
Revenue:
Total revenue		(498)		(1,268)
Cost of revenue:
Total cost of revenue		$ (130)		$ (337)

Restatement of Previously Iss_4

Restatement of Previously Issued Consolidated Financial Statements - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net loss	$ (1,807)	$ (2,245)	$ (26,009)	$ (11,537)
Changes in operating assets and liabilities:
Accounts receivable			(3,144)	11,288
Inventory			1,550	(2,513)
Prepaid expenses and other assets			(868)	(2,785)
Deferred revenue			4,219	(1,245)
Net cash provided by operating activities			$ (5,518)	10,020
As Previously Reported
Cash flows from operating activities:
Net loss		(2,656)		(14,825)
Changes in operating assets and liabilities:
Accounts receivable				16,049
Inventory				(3,242)
Prepaid expenses and other assets				(2,870)
Deferred revenue				(1,904)
Net cash provided by operating activities				10,020
Revenue Recognition Adjustments
Cash flows from operating activities:
Net loss		$ 411		3,288
Changes in operating assets and liabilities:
Accounts receivable				(4,761)
Inventory				729
Prepaid expenses and other assets				85
Deferred revenue				659
Net cash provided by operating activities				$ 0

Marketable Securities and Fai_3

Marketable Securities and Fair Value Measurements - Estimate of Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 87,548	$ 84,690
Gross Unrealized Gains	17	8
Gross Unrealized Losses	(174)	(131)
Fair Value	87,391	84,567
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	14,999	17,000
Gross Unrealized Gains	10	6
Gross Unrealized Losses	(1)	(1)
Fair Value	15,008	17,005
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	47,419	39,154
Gross Unrealized Gains	7	1
Gross Unrealized Losses	(118)	(76)
Fair Value	47,308	39,079
U.S. Treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,747	5,744
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(18)	(19)
Fair Value	3,729	5,725
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,931	9,225
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(3)	(2)
Fair Value	5,928	9,224
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,452	13,567
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(34)	(33)
Fair Value	$ 15,418	$ 13,534

Marketable Securities and Fai_4

Marketable Securities and Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Amortized Cost
Less than 1 year	$ 54,749
Mature in 1 - 3 years	32,799
Amortized Cost	87,548	$ 84,690
Fair Value
Less than 1 year	54,668
Mature in 1 - 3 years	32,723
Fair Value	$ 87,391	$ 84,567

Marketable Securities and Fai_5

Marketable Securities and Fair Value Measurements - Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value
Less Than 12 Months	$ 56,683	$ 56,971
12 Months or More	9,703	5,706
Total	66,386	62,677
Gross Unrealized Losses
Less Than 12 Months	(149)	(111)
12 Months or More	(25)	(20)
Total	(174)	(131)
Certificates of deposit
Fair Value
Less Than 12 Months	2,999	2,999
12 Months or More	0	0
Total	2,999	2,999
Gross Unrealized Losses
Less Than 12 Months	(1)	(1)
12 Months or More	0	0
Total	(1)	(1)
Corporate securities
Fair Value
Less Than 12 Months	38,550	36,079
12 Months or More	2,143	1,499
Total	40,693	37,578
Gross Unrealized Losses
Less Than 12 Months	(110)	(74)
12 Months or More	(8)	(2)
Total	(118)	(76)
U.S. Treasury and agency securities
Fair Value
Less Than 12 Months	1,731	2,246
12 Months or More	1,998	3,479
Total	3,729	5,725
Gross Unrealized Losses
Less Than 12 Months	(16)	(2)
12 Months or More	(2)	(17)
Total	(18)	(19)
Commercial paper
Fair Value
Less Than 12 Months	4,940	4,232
12 Months or More	0	0
Total	4,940	4,232
Gross Unrealized Losses
Less Than 12 Months	(3)	(2)
12 Months or More	0	0
Total	(3)	(2)
Asset-backed securities
Fair Value
Less Than 12 Months	8,463	11,415
12 Months or More	5,562	728
Total	14,025	12,143
Gross Unrealized Losses
Less Than 12 Months	(19)	(32)
12 Months or More	(15)	(1)
Total	$ (34)	$ (33)

Marketable Securities and Fai_6

Marketable Securities and Fair Value Measurements - Schedule of Fair Value of Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financial Assets
Marketable Securities	$ 87,391	$ 84,567
Total	123,553	131,134
Level 1
Financial Assets
Total	36,162	46,567
Level 2
Financial Assets
Total	87,391	84,567
Cash
Financial Assets
Cash and Cash Equivalents	25,688	34,453
Cash | Level 1
Financial Assets
Cash and Cash Equivalents	25,688	34,453
Cash equivalents
Financial Assets
Cash and Cash Equivalents	10,474	12,114
Cash equivalents | Level 1
Financial Assets
Cash and Cash Equivalents	10,474	12,114
Certificates of deposit
Financial Assets
Marketable Securities	15,008	17,005
Certificates of deposit | Level 2
Financial Assets
Marketable Securities	15,008	17,005
Corporate securities
Financial Assets
Marketable Securities	47,308	39,079
Corporate securities | Level 2
Financial Assets
Marketable Securities	47,308	39,079
U.S. Treasury and agency securities
Financial Assets
Marketable Securities	3,729	5,725
U.S. Treasury and agency securities | Level 2
Financial Assets
Marketable Securities	3,729	5,725
Commercial paper
Financial Assets
Marketable Securities	5,928	9,224
Commercial paper | Level 2
Financial Assets
Marketable Securities	5,928	9,224
Asset-backed securities
Financial Assets
Marketable Securities	15,418	13,534
Asset-backed securities | Level 2
Financial Assets
Marketable Securities	$ 15,418	$ 13,534

Condensed Consolidated Financ_3

Condensed Consolidated Financial Statement Details - Schedule of Inventory (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 6,118	$ 6,643
Finished goods	8,984	10,934
Total inventory	$ 15,102	$ 17,577

Condensed Consolidated Financ_4

Condensed Consolidated Financial Statement Details - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 59,034	$ 56,579
Less: accumulated depreciation	(51,040)	(46,666)
Property and equipment, net	7,994	9,913
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	49,930	47,817
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,033	3,988
Furniture and fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	951	950
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,836	3,824
Construction in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 284	$ 0
Minimum | Equipment
Property Plant And Equipment [Line Items]
Useful life	1 year
Minimum | Software
Property Plant And Equipment [Line Items]
Useful life	1 year
Minimum | Furniture and fixtures
Property Plant And Equipment [Line Items]
Useful life	1 year
Minimum | Leasehold improvements
Property Plant And Equipment [Line Items]
Useful life	2 years
Maximum | Equipment
Property Plant And Equipment [Line Items]
Useful life	3 years
Maximum | Software
Property Plant And Equipment [Line Items]
Useful life	3 years
Maximum | Furniture and fixtures
Property Plant And Equipment [Line Items]
Useful life	3 years
Maximum | Leasehold improvements
Property Plant And Equipment [Line Items]
Useful life	8 years

Condensed Consolidated Financ_5

Condensed Consolidated Financial Statement Details - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.5	$ 1.5	$ 4.9	$ 5.1
Amortization expense related to intangible assets	$ 0.4	$ 0.4	$ 1.1	$ 1.1
Weighted average useful life of purchased intangible assets (in years)			2 years 10 months 24 days

Condensed Consolidated Financ_6

Condensed Consolidated Financial Statement Details - Purchased Intangible Assets, net (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	$ 7,986	$ 7,986
Accumulated Amortization	(3,878)	(2,796)
Total	4,108	5,190
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	5,050	5,050
Accumulated Amortization	(2,273)	(1,515)
Total	2,777	3,535
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	2,936	2,936
Accumulated Amortization	(1,605)	(1,281)
Total	$ 1,331	$ 1,655

Condensed Consolidated Financ_7

Condensed Consolidated Financial Statement Details - Future Amortization Expense of Acquired Intangibles (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Remainder of 2018	$ 361
2,019	1,442
2,020	1,442
2,021	863
Total	$ 4,108	$ 5,190

Condensed Consolidated Financ_8

Condensed Consolidated Financial Statement Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 12,003	$ 13,828
Accrued tax liabilities	3,632	2,985
Other	4,967	5,022
Total accrued liabilities	$ 20,602	$ 21,835

Condensed Consolidated Financ_9

Condensed Consolidated Financial Statement Details - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 94,855	$ 94,637
Less: current portion	(60,653)	(61,858)
Non-current portion	34,202	32,779
Products
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	5,109	6,161
Services
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 89,746	$ 88,476

Credit Facility (Details)

Credit Facility (Details) - Line of credit	1 Months Ended
	Sep. 30, 2018USD ($)	Nov. 30, 2016USD ($)
Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument term (in years)		3 years
Maximum borrowing capacity		$ 25,000,000
Debt covenant, net cash equals or exceeds, amount		50,000,000
Debt covenant, net cash falls below, amount		$ 50,000,000
Unused capacity commitment fee		0.40%
Minimum adjusted quick ratio under debt compliance		1.50
Amount outstanding	$ 0
Amended Revolving Credit Facility
Line of Credit Facility [Line Items]
Unused capacity commitment fee	0.30%
Letter of Credit
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 25,000,000
Prime Rate | Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable rate basis spread		0.50%
LIBOR | Revolving Credit Facility
Line of Credit Facility [Line Items]
Variable rate basis spread		2.50%

Equity Incentive Plans and St_3

Equity Incentive Plans and Stock-Based Compensation - 2014 Equity Incentive Plan/ESPP (Details) - USD ($)	Jan. 01, 2018	Jun. 10, 2015	Oct. 31, 2018	Sep. 30, 2018	Oct. 23, 2017
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grant (in shares)				11,580,435
2014 Stock Incentive Plan | Prior Common Stock Outstanding
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of outstanding shares of common stock	5.00%
Additional shares authorized for future issuance (in shares)	3,584,623
2014 Stock Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for reallocation (in shares)		8,310,566
Additional shares reserved for future issuance (in shares)		8,000,000
Percentage of outstanding shares of common stock		5.00%
2014 Employee Stock Purchase Plan | ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grant (in shares)				3,065,182
Percentage of market value				85.00%
Percentage of eligible compensation				15.00%
Common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Authorized amount to be repurchased					$ 20,000,000
Shares repurchased (in shares)				0
Subsequent event | 2014 Employee Stock Purchase Plan | ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of eligible compensation			10.00%

Equity Incentive Plans and St_4

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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,333	$ 4,545	$ 13,055	$ 13,824
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	187	403	1,277	1,068
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	619	1,696	4,085	5,120
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	960	1,537	5,345	5,024
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	567	909	2,348	2,612
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	291	589	922	2,199
Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	2,042	2,969	6,976	9,269
Employee stock purchase rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 0	$ 987	5,157	$ 2,356
Accelerated stock-based compensation			$ 4,100

Equity Incentive Plans and St_5

Equity Incentive Plans and Stock-Based Compensation - Stock-based Compensation/Stock Repurchase Program (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total compensation expense related to unvested awards granted, not yet recognized	$ 18.4
Total compensation expense related to unvested awards granted, not yet recognized weighted-average period for recognition (in years)	1 year 10 months 24 days

Equity Incentive Plans and St_6

Equity Incentive Plans and Stock-Based Compensation - Summary of Activity under Stock Option Plans (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Number of Shares (thousands)
Outstanding options, Beginning balance (in shares)	6,018,000
Granted (in shares)	0
Exercised (in shares)	(359,000)
Canceled (in shares)	(314,000)
Outstanding options, Ending balance (in shares)	5,345,000
Vested and exercisable (in shares)	4,795,000
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 5.18
Granted (in dollars per share)	0
Exercised (in dollars per share)	3.54
Canceled (in dollars per share)	8.84
Ending balance (in dollars per share)	5.07
Vested and exercisable at end of period (in dollars per share)	$ 4.90
Weighted-average remaining contractual term (in years)	4 years 3 months 18 days
Weighted average remaining contractual term, Vested and exercisable at end of period (in years)	3 years 10 months 24 days
Aggregate Intrinsic Value	$ 8,455
Aggregate Intrinsic Value, Vested and exercisable at end of period	$ 8,201
Number of shares canceled under 2008 plan in current reporting period now available under 2014 plan	249,491
Closing price (in dollars per share)	$ 6.08
Intrinsic value of options exercised	$ 1,100	$ 7,000

Equity Incentive Plans and St_7

Equity Incentive Plans and Stock-Based Compensation - Information About Stock Options (Details) - shares	1 Months Ended			9 Months Ended	12 Months Ended
	Oct. 31, 2018	Oct. 31, 2016	Feb. 29, 2016	Sep. 30, 2018	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)				0
MSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)					40,000	540,000
Number of consecutive trading days				20 days
Measurement period				4 years
Vested in period (in shares)				0
PSUs, February 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			547,000
Vested in period (in shares)				178,402
Forfeited in period (in shares)				181,600
Actual performance vesting percentage			80.00%
PSUs, October 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)		60,641
Vested in period (in shares)				30,320
Forfeited in period (in shares)				30,321
Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)				99,000
Vested in period (in shares)				656,000
Forfeited in period (in shares)				854,000
Subsequent event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	300,000
Subsequent event | Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	3,100,000

Equity Incentive Plans and St_8

Equity Incentive Plans and Stock-Based Compensation - Summary of RSU activity (Details) - Restricted Stock - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Unvested at beginning of period (in shares)	5,568
Granted (in shares)	99
Released (in shares)	(656)
Canceled (in shares)	(854)
Unvested at end of period (in shares)	4,157
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Unvested at beginning of period (in dollars per share)	$ 6.88
Granted (in dollars per share)	6.86
Released (in dollars per share)	6.44
Canceled (in dollars per share)	7.38
Unvested at ending of period (in dollars per share)	$ 6.85
Weighted-Average Remaining Vesting Term (years)	1 year 1 month 6 days
Vested in period (in shares)	$ 4.3	$ 12.2

Net Loss Per Share - Summary of

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, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock options, RSUs and employee stock purchase rights
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	8,546	10,071	9,395	12,587

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income tax expense	$ 74	$ 454	$ 660	$ 963
Unrecognized tax benefits	$ 3,800		$ 3,800		$ 3,800

Geographic Information - Schedu

Geographic Information - Schedule of Total Revenue Based on Customer's Location (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 60,502	$ 62,005	$ 170,398	$ 179,912
United States
Segment Reporting Information [Line Items]
Total revenue	27,003	28,951	78,124	92,140
Japan
Segment Reporting Information [Line Items]
Total revenue	14,023	16,634	38,971	38,119
Asia Pacific, excluding Japan
Segment Reporting Information [Line Items]
Total revenue	9,331	7,171	27,436	25,594
EMEA
Segment Reporting Information [Line Items]
Total revenue	8,119	6,117	20,038	18,535
Other
Segment Reporting Information [Line Items]
Total revenue	$ 2,026	$ 3,132	$ 5,829	$ 5,524

Geographic Information - Long L

Geographic Information - Long Lived Assets By Geographic Area (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 7,994	$ 9,913
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	6,080	7,733
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	1,210	1,510
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 704	$ 670

Revenue - Additional Informatio

Revenue - Additional Information (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ 270,637,000	$ 270,637,000		$ 257,025,000
Revenue recognized that was included in deferred revenue balance at January 1, 2018	13,200,000	49,900,000
Asset impairment charges for contract assets		0
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	14,208,000	14,208,000	$ 12,400,000
Deferred revenue	4,000,000	4,000,000
Deferred commissions asset	8,400,000	8,400,000
Deferred Sales Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred contract acquisition costs	8,800,000	8,800,000
Amortization	$ 1,100,000	4,100,000
Impairment loss of contract acquisition costs		$ 0

Revenue - ASC 606 Adjustments (

Revenue - ASC 606 Adjustments (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Assets
Prepaid expenses and other current assets	$ 13,266		$ 13,266			$ 6,825
Other non-current assets	8,380		8,380			4,646
Liabilities
Deferred revenue, current	60,653		60,653		$ 59,360	61,858
Deferred revenue, non-current	34,202		34,202		31,276	32,779
Stockholders' Equity
Accumulated deficit	(270,637)		(270,637)			$ (257,025)
Income Statement
Total revenue	60,502	$ 62,005	170,398	$ 179,912
Gross profit	47,488	48,138	132,313	138,502
Sales and marketing	24,539	26,930	77,231	78,754
Total operating expenses	49,056	49,872	157,569	149,727
Loss from operations	(1,568)	(1,734)	(25,256)	(11,225)
Net loss	$ (1,807)	$ (2,245)	$ (26,009)	$ (11,537)
Basic and diluted (in dollars per share)	$ (0.02)	$ (0.03)	$ (0.36)	$ (0.17)
Adjustments Increase (Decrease)
Assets
Prepaid expenses and other current assets	$ (5,824)		$ (5,824)
Other non-current assets	(3,000)		(3,000)
Liabilities
Deferred revenue, current	3,164		3,164
Deferred revenue, non-current	2,220		2,220
Stockholders' Equity
Accumulated deficit	(14,208)		(14,208)		$ (12,400)
Income Statement
Total revenue	(475)		(1,384)
Gross profit	(475)		(1,384)
Sales and marketing	292		420
Total operating expenses	292		420
Loss from operations	(767)		(1,804)
Net loss	(767)		(1,804)
Balance Without Adopting the New Standard
Assets
Prepaid expenses and other current assets	7,442		7,442
Other non-current assets	5,380		5,380
Liabilities
Deferred revenue, current	63,817		63,817
Deferred revenue, non-current	36,422		36,422
Stockholders' Equity
Accumulated deficit	(284,845)		(284,845)
Income Statement
Total revenue	60,027		169,014
Gross profit	47,013		130,929
Sales and marketing	24,831		77,651
Total operating expenses	49,348		157,989
Loss from operations	(2,335)		(27,060)
Net loss	$ (2,574)		$ (27,813)
Basic and diluted (in dollars per share)	$ (0.04)		$ (0.38)
Products
Income Statement
Total revenue	$ 38,265	$ 40,404	$ 105,638	$ 116,930
Products | Adjustments Increase (Decrease)
Income Statement
Total revenue	(475)		(1,384)
Products | Balance Without Adopting the New Standard
Income Statement
Total revenue	37,790		104,254
Services
Income Statement
Total revenue	22,237	$ 21,601	64,760	$ 62,982
Services | Adjustments Increase (Decrease)
Income Statement
Total revenue	0		0
Services | Balance Without Adopting the New Standard
Income Statement
Total revenue	$ 22,237		$ 64,760

Revenue - Contract Balances (De

Revenue - Contract Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 51,084	$ 48,266	$ 48,266
Deferred revenue	60,653	59,360	61,858
Deferred revenue, non-current	$ 34,202	$ 31,276	$ 32,779

Revenue - Remaining Performance

Revenue - Remaining Performance Obligations (Details) $ in Thousands	Sep. 30, 2018USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 94,855
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 60,653
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 28,350
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 5,852
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period