A10 Networks (ATEN) 10-Q 8 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 30, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Trading Symbol	ATEN
Entity Registrant Name	A10 Networks, Inc.
Entity Central Index Key	0001580808
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		75,634,696

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 33,967	$ 40,621
Marketable securities	88,784	87,754
Accounts receivable, net of allowances of $219 and $319, respectively	44,802	53,972
Inventory	20,952	17,930
Prepaid expenses and other current assets	17,113	14,662
Total current assets	205,618	214,939
Property and equipment, net	7,676	7,262
Goodwill	1,307	1,307
Intangible assets	3,387	3,748
Other non-current assets	13,989	8,620
Total assets	231,977	235,876
LIABILITIES AND STOCKHOLDERS’ EQUITY
Accounts payable	8,136	8,202
Accrued liabilities	25,436	25,291
Deferred revenue	62,528	63,874
Total current liabilities	96,100	97,367
Deferred revenue, non-current	36,041	34,092
Other non-current liabilities	3,062	534
Total liabilities	135,203	131,993
Commitments and contingencies (Note 2 and Note 6)
Stockholders' equity:
Common stock, $0.00001 par value: 500,000 shares authorized; 75,183 and 74,301 shares issued and outstanding, respectively	1	1
Additional paid-in-capital	381,195	376,272
Accumulated other comprehensive income (loss)	96	(144)
Accumulated deficit	(284,518)	(272,246)
Total stockholders' equity	96,774	103,883
Total liabilities and stockholders' equity	$ 231,977	$ 235,876

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Total revenue	$ 50,290	$ 49,183
Cost of revenue:
Total cost of revenue	12,250	11,884
Gross profit	38,040	37,299
Operating expenses:
Sales and marketing	24,483	26,904
Research and development	16,166	18,797
General and administrative	8,358	11,594
Total operating expenses	49,007	57,295
Loss from operations	(10,967)	(19,996)
Non-operating income (expense):
Interest expense	(155)	(33)
Interest and other income (expense), net	(633)	566
Total non-operating income (expense), net	(788)	533
Loss before income taxes	(11,755)	(19,463)
Provision for income taxes	517	207
Net loss	$ (12,272)	$ (19,670)
Net loss per share:
Basic and diluted (in dollars per share)	$ (0.16)	$ (0.27)
Weighted-average shares used in computing net loss per share:
Basic and diluted (in shares)	74,809	72,232
Products
Revenue:
Total revenue	$ 28,230	$ 28,149
Cost of revenue:
Total cost of revenue	7,516	7,109
Services
Revenue:
Total revenue	22,060	21,034
Cost of revenue:
Total cost of revenue	$ 4,734	$ 4,775

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 219	$ 319
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)	75,183,000	74,301,000
Common stock, shares outstanding (in shares)	75,183,000	74,301,000

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (12,272)	$ (19,670)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on marketable securities	240	(173)
Comprehensive loss	$ (12,032)	$ (19,843)

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2017		$ 1	$ 355,533	$ (123)	$ (257,025)
Beginning balance (in shares) at Dec. 31, 2017		71,692
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee equity incentive plans (in shares)		1,015
Common stock issued under employee equity incentive plans		$ 0	1,269
Stock-based compensation			8,151
Unrealized gain (loss) on marketable securities, net of tax				(173)
Cumulative effect adjustment from adoption of ASU 2014-09 | ASU 2014-09					12,397
Net loss	$ (19,670)				(19,670)
Ending balance (in shares) at Mar. 31, 2018		72,707
Ending balance at Mar. 31, 2018	100,360	$ 1	364,953	(296)	(264,298)
Beginning balance at Dec. 31, 2018	103,883	$ 1	376,272	(144)	(272,246)
Beginning balance (in shares) at Dec. 31, 2018		74,301
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued under employee equity incentive plans (in shares)		882
Common stock issued under employee equity incentive plans		$ 0	1,027
Stock-based compensation			3,896
Unrealized gain (loss) on marketable securities, net of tax				240
Cumulative effect adjustment from adoption of ASU 2014-09 | ASU 2014-09					0
Net loss	(12,272)				(12,272)
Ending balance (in shares) at Mar. 31, 2019		75,183
Ending balance at Mar. 31, 2019	$ 96,774	$ 1	$ 381,195	$ 96	$ (284,518)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net loss	$ (12,272)	$ (19,670)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,447	2,134
Stock-based compensation	3,896	8,151
Other non-cash items	(246)	389
Changes in operating assets and liabilities:
Accounts receivable	9,285	94
Inventory	(3,325)	827
Prepaid expenses and other assets	(2,409)	(1,687)
Accounts payable	(492)	(1,202)
Accrued and other liabilities	(3,616)	3,599
Deferred revenue	603	6,995
Other	71	18
Net cash used in operating activities	(6,058)	(352)
Cash flows from investing activities:
Proceeds from sales of marketable securities	8,674	10,709
Proceeds from maturities of marketable securities	4,500	17,150
Purchases of marketable securities	(13,859)	(27,220)
Purchases of property and equipment	(936)	(1,133)
Net cash used in investing activities	(1,621)	(494)
Cash flows from financing activities:
Proceeds from issuance of common stock under employee equity incentive plans	1,027	1,269
Other	(2)	(26)
Net cash provided by financing activities	1,025	1,243
Net (decrease) increase in cash and cash equivalents	(6,654)	397
Cash and cash equivalents - beginning of period	40,621	46,567
Cash and cash equivalents - end of period	33,967	46,964
Non-cash investing and financing activities:
Inventory transfers to property and equipment	303	561
Purchases of property and equipment included in accounts payable	$ 485	$ 87

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
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 consists of six secure application solutions: Thunder Application Delivery Controller (“ADC”), Lightning Application Delivery Controller (“Lightning ADC”), Thunder Carrier Grade Networking (“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 TPS. Our solutions are available in a variety of form factors, such as optimized hardware appliances, bare metal software, containerized 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, 2018 has been derived from our audited financial statements, which are included in our 2018 Annual Report on Form 10-K for the year ended December 31, 2018 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. 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, 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, 2018. Other than the accounting policies related to the adoption of Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) discussed below, there have been no material changes to the Company’s significant accounting policies during the three months ended March 31, 2019 . Leases The Company determines if an arrangement is a lease at inception. For leases where the Company is the lessee, right-of-use (“ROU”) assets represent the Company’s right to use the underlying asset for the term of the lease and are included within other non-current assets on the condensed consolidated balance sheets, and the lease liabilities represent an obligation to make lease payments arising from the lease and are recorded within accrued liabilities and other non-current liabilities on the condensed consolidated balance sheets. Lease liabilities are recognized at the lease commencement date based on the present value of the future lease payments over the lease term. The Company uses its incremental borrowing rate based on the information available at the commencement date of the underlying lease arrangement to determine the present value of lease payments. The ROU asset is determined based on the lease liability initially established and reduced for any prepaid lease payments and any lease incentives received. The lease term to calculate the ROU asset and related lease liability includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. The Company’s lease agreements generally do not contain any material variable lease payments, residual value guarantees or restrictive covenants. The Company elected the package of practical expedients permitted under the transition guidance, which allowed for the carry-forward of the Company’s historical lease classification and assessment on whether a contract is or contains a lease. The Company elected to not apply the new standard’s recognition requirements to leases with an initial term of 12 months or less and instead elected to recognize lease payments in the condensed consolidated statements of operations on a straight-line basis over the lease term. The Company did not elect to apply the hindsight practical expedient when determining lease term and assessing impairment of right-of-use assets. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense while expense for financing leases is recognized as depreciation expense and interest expense using the accelerated interest method of recognition. The Company accounts for lease components and non-lease components as a single lease component. 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 March 31, 2019 2018 Customer A (a distribution channel partner) 13% * * represents less than 10% of total revenue As of March 31, 2019 , two customers accounted for 26% and 10% , respectively, of our total gross accounts receivable. As of December 31, 2018 , two customers accounted for 16% and 12% , respectively, of our total gross accounts receivable. Recently Adopted Accounting Guidance In February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under prior generally accepted accounting principles. ASU 2016-02 requires that a lessee should recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. The adoption of ASU 2016-02 on January 1, 2019 resulted in the recognition of right-of-use assets of approximately $6.0 million and lease liabilities for operating leases of approximately $6.8 million on the Company’s condensed consolidated balance sheets, with no material impact to its condensed consolidated statements of operations. See Note 2 for further information regarding the impact of the adoption of ASU 2016-02 on the Company's financial statements. Recent Accounting Pronouncements Not Yet Effective There have been no new accounting pronouncements issued by the FASB during the three months ended March 31, 2019, as compared to the recent accounting pronouncements described in Note 1 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, that the Company believes are of significance or potential significance to the Company.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases We lease various operating spaces in the United States, Asia and Europe under non-cancellable 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. The table below presents the Company’s right-of-use assets and lease liabilities as of March 31, 2019: March 31, 2019 Operating leases Right-of-use assets: Other non-current assets $ 5,450 Total right-of-use assets $ 5,450 Lease liabilities: Accrued liabilities $ 3,506 Other non-current liabilities 2,609 Total operating lease liabilities $ 6,115 The aggregate future lease payments for operating leases as of March 31, 2019 were as follows: Remainder of 2019 $ 2,866 2020 1,960 2021 1,197 2022 312 Total lease payments 6,335 Less: imputed interest (220 ) Present value of lease liabilities $ 6,115 The components of operating lease costs were as follows: Three Months Ended March 31, 2019 Operating lease costs $ 893 Short-term lease costs 137 Total lease costs $ 1,030 Average lease terms and discount rates for the Company’s operating leases were as follows: March 31, 2019 Weighted-average remaining term (years) 2.17 Weighted-average discount rate 3.41 % Supplemental cash flow information for the Company’s operating leases: Three Months Ended March 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 989 Right-of-use assets obtained in exchange for new lease liabilities $ 264

Marketable Securities and Fair

Marketable Securities and Fair Value Measurements	3 Months Ended
	Mar. 31, 2019
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): March 31, 2019 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 11,998 $ 24 $ — $ 12,022 $ 11,000 $ 7 $ (3 ) $ 11,004 Corporate securities 48,217 89 (33 ) 48,273 46,442 11 (116 ) 46,337 U.S. Treasury and agency securities 1,748 — (6 ) 1,742 1,748 — (12 ) 1,736 Commercial paper 11,410 8 — 11,418 12,327 1 (5 ) 12,323 Asset-backed securities 15,315 22 (8 ) 15,329 16,381 5 (32 ) 16,354 Total $ 88,688 $ 143 $ (47 ) $ 88,784 $ 87,898 $ 24 $ (168 ) $ 87,754 During the three months ended March 31, 2019 and 2018 , 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 March 31, 2019 (in thousands): Amortized Cost Fair Value Less than 1 year $ 57,747 $ 57,746 Mature in 1 - 3 years 30,941 31,038 Total $ 88,688 $ 88,784 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 March 31, 2019 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate securities $ 4,247 $ (1 ) $ 10,365 $ (32 ) $ 14,612 $ (33 ) U.S. Treasury and agency securities — — 1,742 (6 ) 1,742 (6 ) Asset-backed securities 996 — 3,616 (8 ) 4,612 (8 ) Total $ 5,243 $ (1 ) $ 15,723 $ (46 ) $ 20,966 $ (47 ) Less Than 12 Months 12 Months or More Total December 31, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,997 $ (3 ) $ — $ — $ 2,997 $ (3 ) Corporate securities 29,435 (68 ) 7,601 (48 ) 37,036 (116 ) U.S. Treasury and agency securities 992 (7 ) 744 (5 ) 1,736 (12 ) Commercial paper 9,888 (5 ) — — 9,888 (5 ) Asset-backed securities 8,499 (15 ) 4,758 (17 ) 13,257 (32 ) Total $ 51,811 $ (98 ) $ 13,103 $ (70 ) $ 64,914 $ (168 ) 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 three months ended March 31, 2019 and 2018 . 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): March 31, 2019 December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash $ 32,615 $ — $ — $ 32,615 $ 39,113 $ — $ — $ 39,113 Cash equivalents 1,352 — — 1,352 1,508 — — 1,508 Certificates of deposit — 12,022 — 12,022 — 11,004 — 11,004 Corporate securities — 48,273 — 48,273 — 46,337 — 46,337 U.S. Treasury and agency securities — 1,742 — 1,742 — 1,736 — 1,736 Commercial paper — 11,418 — 11,418 — 12,323 — 12,323 Asset-backed securities — 15,329 — 15,329 — 16,354 — 16,354 Total $ 33,967 $ 88,784 $ — $ 122,751 $ 40,621 $ 87,754 $ — $ 128,375 There were no transfers between Level 1 and Level 2 fair value measurement categories during the three months ended March 31, 2019 and 2018 .

Condensed Consolidated Financia

Condensed Consolidated Financial Statement Details	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Condensed Consolidated Financial Statement Details	Condensed Consolidated Financial Statement Details Inventory Inventory consisted of the following (in thousands): March 31, December 31, Raw materials $ 8,502 $ 7,979 Finished goods 12,450 9,951 Total inventory $ 20,952 $ 17,930 Prepaid Expenses and Other Current Assets Prepaid expenses and other current assets consisted of the following (in thousands): March 31, December 31, Prepaid expenses $ 6,675 $ 6,679 Deferred contract acquisition costs 5,711 6,564 Other 4,727 1,419 Total prepaid and other current assets $ 17,113 $ 14,662 Property and Equipment, Net Property and equipment, net, consisted of the following (in thousands): Useful Life March 31, December 31, (in years) Equipment 1-3 $ 49,230 $ 49,804 Software 1-3 4,108 4,088 Furniture and fixtures 1-3 967 967 Leasehold improvements 2-8 3,834 3,832 Construction in progress 692 160 Property and equipment, gross 58,831 58,851 Less: accumulated depreciation (51,155 ) (51,589 ) Property and equipment, net $ 7,676 $ 7,262 Depreciation expense on property and equipment was $1.2 million and $1.7 million for the three months ended March 31, 2019 and 2018 , respectively. Intangible Assets Purchased intangible assets, net, consisted of the following (in thousands): March 31, 2019 December 31, 2018 Cost Accumulated Amortization Net Cost Accumulated Amortization Net Developed technology $ 5,050 $ (2,778 ) $ 2,272 $ 5,050 $ (2,525 ) $ 2,525 Patents 2,936 (1,821 ) 1,115 2,936 (1,713 ) 1,223 Total $ 7,986 $ (4,599 ) $ 3,387 $ 7,986 $ (4,238 ) $ 3,748 Amortization expense related to purchased intangible assets was $0.4 million for each of the three months ended March 31, 2019 and 2018 . Purchased intangible assets will be amortized over a remaining weighted average useful life of 2.4 years. Future amortization expense for purchased intangible assets as of March 31, 2019 is as follows (in thousands): Fiscal Year Remainder of 2019 $ 1,082 2020 1,442 2021 863 $ 3,387 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued compensation and benefits $ 11,605 $ 15,283 Accrued tax liabilities 5,555 4,455 Other 8,276 5,553 Total accrued liabilities $ 25,436 $ 25,291 Deferred Revenue Deferred revenue consisted of the following (in thousands): March 31, December 31, Deferred revenue: Products $ 5,529 $ 5,216 Services 93,040 92,750 Total deferred revenue 98,569 97,966 Less: current portion (62,528 ) (63,874 ) Non-current portion $ 36,041 $ 34,092

Credit Facility

Credit Facility	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 , we had no outstanding balance under the 2016 Credit Facility and were in compliance with all facility covenants.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2019
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. The amended complaint named the same defendants as the initial complaint, in addition to one of the Company’s former executive vice presidents. The Company and individual defendants filed motions to dismiss the amended complaint. On February 21, 2019, the court granted the motions to dismiss with leave to amend within 21 days. The lead plaintiff did not file an amended complaint by the Court-ordered deadline. Instead, on March 21, 2019, the lead plaintiff filed a notice of appeal in the United States Court of Appeals for the Ninth Circuit. On April 5, 2019, the clerk of court suspended briefing on the appeal and ordered that, by April 26, 2019, appellants shall either move for voluntary dismissal or show cause why the appeal should not be dismissed for lack of jurisdiction. On April 25, 2019, appellants moved to voluntarily dismiss the appeal without prejudice, and that motion was granted on May 1, 2019. Prior to moving to voluntarily dismiss the appeal, the lead plaintiff requested entry of final judgment in the district court. On April 30, 2019, the district court ordered a response to that request by May 14, 2019, with a reply by lead plaintiff due by May 21, 2019. 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 alleged infringement of certain patents purportedly owned by the plaintiff. In January 2019, we entered into a settlement agreement whereby we obtained a fully-paid up license, and the case was dismissed with prejudice on February 4, 2019. 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. 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	3 Months Ended
	Mar. 31, 2019
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. 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, effective January 1, 2019 , the number of shares in the 2014 Plan increased by 3,715,060 shares, representing 5% of the prior year end’s common stock outstanding. As of March 31, 2019, we had 12,613,705 shares available for future grant under the 2014 Plan. To date, we have granted stock options, RSUs and PSUs under the 2014 Plan. Stock options expire no more than 10 years from the grant date and generally vest over four years . In the case of an incentive stock option granted to an employee who, at the time of grant, owns stock representing more than 10% of the total combined voting power of all classes of stock, the per share exercise price will be no less than 110% of the fair market value per share on the date of grant, and the incentive stock option will expire no later than five years from the date of grant. For incentive stock options granted to any other employees and nonstatutory stock options granted to employees, consultants, or members of our board of directors, the per share exercise price will be no less than 100% of the fair market value per share on the date of grant. RSUs and PSUs generally vest over one to four years . 2014 Employee Stock Purchase Plan The 2014 Employee Stock Purchase Plan (the “2014 Purchase Plan”) was suspended effective March 16, 2018 due to the delay of the Form 10-K filing for the year ended December 31, 2017. In October 2018, the Board approved amending the 2014 Purchase Plan (the “Amended 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. The Amended 2014 Purchase Plan also reflects revised offering periods, which were changed from 24 months to six months in duration and that begin on or about December 1 and June 1 each year, starting in December 2018. The Amended 2014 Purchase Plan permits eligible employees to purchase shares of our common stock through payroll deductions with up to 10% of their gross eligible earnings subject to certain Internal Revenue Code limitations. The purchase price of the shares is 85% of the lower of the fair market value of our common stock on the first day of a six-month offering period or the relevant purchase date. In addition, no participant may purchase more than 1,500 shares of common stock in each purchase period. As of March 31, 2019, the Company had 3,065,182 shares available for future issuance under the Amended 2014 Purchase Plan. During the three months ended March 31, 2019, there was no stock purchased by employees under the Amended 2014 Purchase Plan. Stock-Based Compensation A summary of our stock-based compensation expense is as follows (in thousands): Three Months Ended March 31, 2019 2018 Stock-based compensation by type of award: Stock options $ 184 $ 329 Stock awards 3,474 2,665 Employee stock purchase rights (1) 238 5,157 $ 3,896 $ 8,151 Stock-based compensation by category of expense: Cost of revenue $ 324 $ 893 Sales and marketing 1,321 2,765 Research and development 1,331 3,382 General and administrative 920 1,111 $ 3,896 $ 8,151 (1) Amount for the three months ended March 31, 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 the 2014 Purchase Plan was accelerated and recognized within the condensed consolidated statement of operations. As of March 31, 2019 , the Company had $28.7 million of unrecognized stock-based compensation expense related to unvested stock-based awards which will be recognized over a weighted-average period of 2.5 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, 2018 4,674 $ 5.19 Granted — $ — Exercised (305 ) $ 3.36 Canceled (47 ) $ 8.10 Outstanding as of March 31, 2019 4,322 $ 5.28 4.9 $ 9,498 Vested and exercisable as of March 31, 2019 3,855 $ 5.14 4.4 $ 9,061 As of March 31, 2019 , the aggregate intrinsic value represents the excess of the closing price of our common stock of $7.09 over the exercise price of the outstanding in-the-money options. The intrinsic value of options exercised was $1.1 million during each of the three months ended March 31, 2019 and 2018 . 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. As of March 31, 2019, none of these MSUs were vested and all of the MSUs granted in 2014 were expired. 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 previously disclosed restatement of the 2016 consolidated financial statements. As of March 31, 2019 , 253,203 shares had vested, 200,297 shares were forfeited, and the remaining shares will vest (as to 80% ) in 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 March 31, 2019 , 30,320 shares were vested and 30,321 shares were forfeited. In October 2018, we granted 464,888 PSUs with certain financial targets. These PSUs will become eligible to vest at 75% upon the achievement of the performance targets by December 31, 2020, and are subject to service condition vesting requirements. The remaining 25% of these PSUs will become eligible to vest on the first anniversary of the initial vesting date. None of these PSUs were vested as of March 31, 2019. 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) Nonvested as of December 31, 2018 5,974 $ 6.51 Granted 248 $ 6.87 Released (577 ) $ 6.30 Canceled (259 ) $ 6.72 Nonvested as of March 31, 2019 5,386 $ 6.54 1.5 The aggregate fair value of stock awards released as of the respective vesting dates was $3.8 million and $4.3 million for the three months ended March 31, 2019 and 2018 , respectively.

Net Loss Per Share

Net Loss Per Share	3 Months Ended
	Mar. 31, 2019
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 months ended March 31, 2019 and 2018 , 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 March 31, 2019 2018 Stock options, restricted stock units and employee stock purchase rights 9,997 10,431

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes We recorded income tax expense of $0.5 million and $0.2 million for the three months ended March 31, 2019 and 2018, 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 March 31, 2019. 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 $4.2 million of unrecognized tax benefits as of March 31, 2019 and December 31, 2018. 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 2005 through the current period. We are not currently under examination by any taxing authorities.

Geographic Information

Geographic Information	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 United States $ 18,100 $ 20,678 Japan 13,152 13,080 Asia Pacific, excluding Japan 8,776 7,438 EMEA 7,229 6,499 Other 3,033 1,488 $ 50,290 $ 49,183 The following table is a summary of our long-lived assets which include property and equipment, net and operating lease ROU assets based on the physical location of the assets (in thousands): March 31, December 31, United States $ 7,652 $ 5,525 Japan 3,488 1,108 Other 1,986 629 Total $ 13,126 $ 7,262

Revenue Revenue

Revenue Revenue	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue	Revenue 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 consolidated balance sheet. The Company adopted ASU 2014-09 and its related amendments (collectively “ASC 606”) on January 1, 2018 using the modified retrospective method. The adoption of the new standard resulted in changes to the Company’s accounting policies for revenue recognition, commissions and deferred commissions. As a result of the adoption, the Company 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. For additional information and disclosure of the impact of adopting the new standard, see Note 2 to the Company’s Consolidated Financial Statements included in Part II, Item 8 of our Annual Report on Form 10-K for the year ended December 31, 2018. Contract Balances The following table reflects contract balances with customers (in thousands): March 31, 2019 December 31, 2018 Accounts receivable, net $ 44,802 $ 53,972 Deferred revenue, current 62,528 63,874 Deferred revenue, non-current 36,041 34,092 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 March 31, 2019 . 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 months ended March 31, 2019 and 2018, we recognized revenue of $23.7 million and $19.5 million , respectively, related to deferred revenues at the beginning of the respective periods. 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 $9.0 million as of March 31, 2019 , and the related amortization amount was $2.0 million and $1.7 million for the three months ended March 31, 2019 and March 31, 2018, respectively. 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 include 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): March 31, 2019 Within 1 year $ 62,528 Next 2 to 3 years 29,469 Thereafter 6,572 Total $ 98,569

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	Subsequent Event Lease of 2300 Orchard Parkway On May 2, 2019 (the “Effective Date”), the Company entered into a sublease agreement (the “Sublease”) with Marvell Semiconductor, Inc. (“Sublandlord”) for corporate office space located at 2300 Orchard Parkway, San Jose, California, 95131 (the “Premises”). The Sublease is conditioned upon receipt of consent to the Sublease from the landlord of the Premises, Han’s Holdings 2300 Orchard (the “Landlord”). The Company intends to use the premises as a corporate office space and for research and development purposes. The term of the Sublease is seven years and eight months from the earlier of (i) December 1, 2019 or (ii) the date the Company commences business operations at the Premises. The Sublease provides for monthly base rent of approximately $262,000 per month for the first year with annual increases thereafter. The total base rent through the end of the term of the Sublease is approximately $26.4 million . In addition to base rent, the Company will also be responsible for operating and other expenses. The Company is evaluating the accounting for the new sublease arrangement under ASC 842.

Description of Business and S_2

Description of Business and Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
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, 2018 has been derived from our audited financial statements, which are included in our 2018 Annual Report on Form 10-K for the year ended December 31, 2018 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.
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, 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.
Leases	Leases The Company determines if an arrangement is a lease at inception. For leases where the Company is the lessee, right-of-use (“ROU”) assets represent the Company’s right to use the underlying asset for the term of the lease and are included within other non-current assets on the condensed consolidated balance sheets, and the lease liabilities represent an obligation to make lease payments arising from the lease and are recorded within accrued liabilities and other non-current liabilities on the condensed consolidated balance sheets. Lease liabilities are recognized at the lease commencement date based on the present value of the future lease payments over the lease term. The Company uses its incremental borrowing rate based on the information available at the commencement date of the underlying lease arrangement to determine the present value of lease payments. The ROU asset is determined based on the lease liability initially established and reduced for any prepaid lease payments and any lease incentives received. The lease term to calculate the ROU asset and related lease liability includes options to extend or terminate the lease when it is reasonably certain that the Company will exercise the option. The Company’s lease agreements generally do not contain any material variable lease payments, residual value guarantees or restrictive covenants. The Company elected the package of practical expedients permitted under the transition guidance, which allowed for the carry-forward of the Company’s historical lease classification and assessment on whether a contract is or contains a lease. The Company elected to not apply the new standard’s recognition requirements to leases with an initial term of 12 months or less and instead elected to recognize lease payments in the condensed consolidated statements of operations on a straight-line basis over the lease term. The Company did not elect to apply the hindsight practical expedient when determining lease term and assessing impairment of right-of-use assets. Lease expense for operating leases is recognized on a straight-line basis over the lease term as an operating expense while expense for financing leases is recognized as depreciation expense and interest expense using the accelerated interest method of recognition. The Company accounts for lease components and non-lease components as a single lease component.
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 February 2016, the Financial Accounting Standards Board ("FASB") issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under prior generally accepted accounting principles. ASU 2016-02 requires that a lessee should recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. The adoption of ASU 2016-02 on January 1, 2019 resulted in the recognition of right-of-use assets of approximately $6.0 million and lease liabilities for operating leases of approximately $6.8 million on the Company’s condensed consolidated balance sheets, with no material impact to its condensed consolidated statements of operations. See Note 2 for further information regarding the impact of the adoption of ASU 2016-02 on the Company's financial statements. Recent Accounting Pronouncements Not Yet Effective There have been no new accounting pronouncements issued by the FASB during the three months ended March 31, 2019, as compared to the recent accounting pronouncements described in Note 1 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, that the Company believes are of significance or potential significance to the Company.
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)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 Customer A (a distribution channel partner) 13% * * represents less than 10% of total revenue

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Assets And Liabilities,	The table below presents the Company’s right-of-use assets and lease liabilities as of March 31, 2019: March 31, 2019 Operating leases Right-of-use assets: Other non-current assets $ 5,450 Total right-of-use assets $ 5,450 Lease liabilities: Accrued liabilities $ 3,506 Other non-current liabilities 2,609 Total operating lease liabilities $ 6,115
Lease Payments	The aggregate future lease payments for operating leases as of March 31, 2019 were as follows: Remainder of 2019 $ 2,866 2020 1,960 2021 1,197 2022 312 Total lease payments 6,335 Less: imputed interest (220 ) Present value of lease liabilities $ 6,115
Lease Costs	The components of operating lease costs were as follows: Three Months Ended March 31, 2019 Operating lease costs $ 893 Short-term lease costs 137 Total lease costs $ 1,030 Average lease terms and discount rates for the Company’s operating leases were as follows: March 31, 2019 Weighted-average remaining term (years) 2.17 Weighted-average discount rate 3.41 % Supplemental cash flow information for the Company’s operating leases: Three Months Ended March 31, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 989 Right-of-use assets obtained in exchange for new lease liabilities $ 264

Marketable Securities and Fai_2

Marketable Securities and Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Available-for-sale Securities	Marketable securities, classified as available-for-sale, consisted of the following (in thousands): March 31, 2019 December 31, 2018 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Certificates of deposit $ 11,998 $ 24 $ — $ 12,022 $ 11,000 $ 7 $ (3 ) $ 11,004 Corporate securities 48,217 89 (33 ) 48,273 46,442 11 (116 ) 46,337 U.S. Treasury and agency securities 1,748 — (6 ) 1,742 1,748 — (12 ) 1,736 Commercial paper 11,410 8 — 11,418 12,327 1 (5 ) 12,323 Asset-backed securities 15,315 22 (8 ) 15,329 16,381 5 (32 ) 16,354 Total $ 88,688 $ 143 $ (47 ) $ 88,784 $ 87,898 $ 24 $ (168 ) $ 87,754
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 March 31, 2019 (in thousands): Amortized Cost Fair Value Less than 1 year $ 57,747 $ 57,746 Mature in 1 - 3 years 30,941 31,038 Total $ 88,688 $ 88,784
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 March 31, 2019 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Corporate securities $ 4,247 $ (1 ) $ 10,365 $ (32 ) $ 14,612 $ (33 ) U.S. Treasury and agency securities — — 1,742 (6 ) 1,742 (6 ) Asset-backed securities 996 — 3,616 (8 ) 4,612 (8 ) Total $ 5,243 $ (1 ) $ 15,723 $ (46 ) $ 20,966 $ (47 ) Less Than 12 Months 12 Months or More Total December 31, 2018 Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Fair Value Gross Unrealized Losses Certificates of deposit $ 2,997 $ (3 ) $ — $ — $ 2,997 $ (3 ) Corporate securities 29,435 (68 ) 7,601 (48 ) 37,036 (116 ) U.S. Treasury and agency securities 992 (7 ) 744 (5 ) 1,736 (12 ) Commercial paper 9,888 (5 ) — — 9,888 (5 ) Asset-backed securities 8,499 (15 ) 4,758 (17 ) 13,257 (32 ) Total $ 51,811 $ (98 ) $ 13,103 $ (70 ) $ 64,914 $ (168 )
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): March 31, 2019 December 31, 2018 Level 1 Level 2 Level 3 Total Level 1 Level 2 Level 3 Total Cash $ 32,615 $ — $ — $ 32,615 $ 39,113 $ — $ — $ 39,113 Cash equivalents 1,352 — — 1,352 1,508 — — 1,508 Certificates of deposit — 12,022 — 12,022 — 11,004 — 11,004 Corporate securities — 48,273 — 48,273 — 46,337 — 46,337 U.S. Treasury and agency securities — 1,742 — 1,742 — 1,736 — 1,736 Commercial paper — 11,418 — 11,418 — 12,323 — 12,323 Asset-backed securities — 15,329 — 15,329 — 16,354 — 16,354 Total $ 33,967 $ 88,784 $ — $ 122,751 $ 40,621 $ 87,754 $ — $ 128,375

Condensed Consolidated Financ_2

Condensed Consolidated Financial Statement Details (Tables)	3 Months Ended
	Mar. 31, 2019
Property, Plant and Equipment [Abstract]
Schedule of Inventory	Inventory consisted of the following (in thousands): March 31, December 31, Raw materials $ 8,502 $ 7,979 Finished goods 12,450 9,951 Total inventory $ 20,952 $ 17,930
Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): March 31, December 31, Prepaid expenses $ 6,675 $ 6,679 Deferred contract acquisition costs 5,711 6,564 Other 4,727 1,419 Total prepaid and other current assets $ 17,113 $ 14,662
Schedule of Property and Equipment, Net	Property and equipment, net, consisted of the following (in thousands): Useful Life March 31, December 31, (in years) Equipment 1-3 $ 49,230 $ 49,804 Software 1-3 4,108 4,088 Furniture and fixtures 1-3 967 967 Leasehold improvements 2-8 3,834 3,832 Construction in progress 692 160 Property and equipment, gross 58,831 58,851 Less: accumulated depreciation (51,155 ) (51,589 ) Property and equipment, net $ 7,676 $ 7,262
Schedule of Acquired Intangible Assets	Purchased intangible assets, net, consisted of the following (in thousands): March 31, 2019 December 31, 2018 Cost Accumulated Amortization Net Cost Accumulated Amortization Net Developed technology $ 5,050 $ (2,778 ) $ 2,272 $ 5,050 $ (2,525 ) $ 2,525 Patents 2,936 (1,821 ) 1,115 2,936 (1,713 ) 1,223 Total $ 7,986 $ (4,599 ) $ 3,387 $ 7,986 $ (4,238 ) $ 3,748
Schedule of Future Amortization Expense for Purchased Finite-lived Intangible Assets	Future amortization expense for purchased intangible assets as of March 31, 2019 is as follows (in thousands): Fiscal Year Remainder of 2019 $ 1,082 2020 1,442 2021 863 $ 3,387
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): March 31, December 31, Accrued compensation and benefits $ 11,605 $ 15,283 Accrued tax liabilities 5,555 4,455 Other 8,276 5,553 Total accrued liabilities $ 25,436 $ 25,291
Schedule of Deferred Revenue	Deferred revenue consisted of the following (in thousands): March 31, December 31, Deferred revenue: Products $ 5,529 $ 5,216 Services 93,040 92,750 Total deferred revenue 98,569 97,966 Less: current portion (62,528 ) (63,874 ) Non-current portion $ 36,041 $ 34,092

Equity Incentive Plans and St_2

Equity Incentive Plans and Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 Stock-based compensation by type of award: Stock options $ 184 $ 329 Stock awards 3,474 2,665 Employee stock purchase rights (1) 238 5,157 $ 3,896 $ 8,151 Stock-based compensation by category of expense: Cost of revenue $ 324 $ 893 Sales and marketing 1,321 2,765 Research and development 1,331 3,382 General and administrative 920 1,111 $ 3,896 $ 8,151 (1) Amount for the three months ended March 31, 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 the 2014 Purchase Plan 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, 2018 4,674 $ 5.19 Granted — $ — Exercised (305 ) $ 3.36 Canceled (47 ) $ 8.10 Outstanding as of March 31, 2019 4,322 $ 5.28 4.9 $ 9,498 Vested and exercisable as of March 31, 2019 3,855 $ 5.14 4.4 $ 9,061
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) Nonvested as of December 31, 2018 5,974 $ 6.51 Granted 248 $ 6.87 Released (577 ) $ 6.30 Canceled (259 ) $ 6.72 Nonvested as of March 31, 2019 5,386 $ 6.54 1.5

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 Stock options, restricted stock units and employee stock purchase rights 9,997 10,431

Geographic Information (Tables)

Geographic Information (Tables)	3 Months Ended
	Mar. 31, 2019
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 March 31, 2019 2018 United States $ 18,100 $ 20,678 Japan 13,152 13,080 Asia Pacific, excluding Japan 8,776 7,438 EMEA 7,229 6,499 Other 3,033 1,488 $ 50,290 $ 49,183
Long-lived Assets by Geographic Areas	The following table is a summary of our long-lived assets which include property and equipment, net and operating lease ROU assets based on the physical location of the assets (in thousands): March 31, December 31, United States $ 7,652 $ 5,525 Japan 3,488 1,108 Other 1,986 629 Total $ 13,126 $ 7,262

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2019
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset and Liability	The following table reflects contract balances with customers (in thousands): March 31, 2019 December 31, 2018 Accounts receivable, net $ 44,802 $ 53,972 Deferred revenue, current 62,528 63,874 Deferred revenue, non-current 36,041 34,092
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	We expect to recognize revenue on the remaining performance obligations as follows (in thousands): March 31, 2019 Within 1 year $ 62,528 Next 2 to 3 years 29,469 Thereafter 6,572 Total $ 98,569

Description of Business and S_4

Description of Business and Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)toolsolution	Jan. 01, 2019USD ($)
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
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU asset	$ 5,450
Present value of lease liabilities	$ 6,115
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
ROU asset		$ 6,000
Present value of lease liabilities		$ 6,800

Description of Business and S_5

Description of Business and Summary of Significant Accounting Policies - Concentration Risk (Details)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Customer A | Revenue
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)	13.00%
Customer A | Accounts Receivable
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)	26.00%	16.00%
Customer B | Accounts Receivable
Entity Wide Revenue Major Customer [Line Items]
Percentage representation of significant customers (percent)	10.00%	12.00%

Leases - Assets and Liabilities

Leases - Assets and Liabilities (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Total right-of-use assets	$ 5,450
Accrued liabilities	3,506
Other non-current liabilities	2,609
Total operating lease liabilities	$ 6,115

Leases - Lease Liabilities (Det

Leases - Lease Liabilities (Details) $ in Thousands	Mar. 31, 2019USD ($)
Leases [Abstract]
Remainder of 2019	$ 2,866
2020	1,960
2021	1,197
2022	312
Total lease payments	6,335
Less: imputed interest	(220)
Present value of lease liabilities	$ 6,115

Leases - Lease Costs (Details)

Leases - Lease Costs (Details)	3 Months Ended
	Mar. 31, 2019USD ($)
Leases [Abstract]
Operating lease costs	$ 893
Short-term lease costs	137
Total lease costs	$ 1,030
Weighted-average remaining term (years)	2 years 2 months
Weighted-average discount rate	3.41%
Operating cash flows from operating leases	$ 989
Right-of-use assets obtained in exchange for new lease liabilities	$ 264,000

Marketable Securities and Fai_3

Marketable Securities and Fair Value Measurements - Estimate of Fair Value of Marketable Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 88,688	$ 87,898
Gross Unrealized Gains	143	24
Gross Unrealized Losses	(47)	(168)
Fair Value	88,784	87,754
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,998	11,000
Gross Unrealized Gains	24	7
Gross Unrealized Losses	0	(3)
Fair Value	12,022	11,004
Corporate securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	48,217	46,442
Gross Unrealized Gains	89	11
Gross Unrealized Losses	(33)	(116)
Fair Value	48,273	46,337
U.S. Treasury and agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,748	1,748
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(6)	(12)
Fair Value	1,742	1,736
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,410	12,327
Gross Unrealized Gains	8	1
Gross Unrealized Losses	0	(5)
Fair Value	11,418	12,323
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,315	16,381
Gross Unrealized Gains	22	5
Gross Unrealized Losses	(8)	(32)
Fair Value	$ 15,329	$ 16,354

Marketable Securities and Fai_4

Marketable Securities and Fair Value Measurements - Contractual Maturities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Amortized Cost
Less than 1 year	$ 57,747
Mature in 1 - 3 years	30,941
Amortized Cost	88,688	$ 87,898
Fair Value
Less than 1 year	57,746
Mature in 1 - 3 years	31,038
Fair Value	$ 88,784	$ 87,754

Marketable Securities and Fai_5

Marketable Securities and Fair Value Measurements - Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value
Less Than 12 Months	$ 5,243	$ 51,811
12 Months or More	15,723	13,103
Total	20,966	64,914
Gross Unrealized Losses
Less Than 12 Months	(1)	(98)
12 Months or More	(46)	(70)
Total	(47)	(168)
Certificates of deposit
Fair Value
Less Than 12 Months		2,997
12 Months or More		0
Total		2,997
Gross Unrealized Losses
Less Than 12 Months		(3)
12 Months or More		0
Total		(3)
Corporate securities
Fair Value
Less Than 12 Months	4,247	29,435
12 Months or More	10,365	7,601
Total	14,612	37,036
Gross Unrealized Losses
Less Than 12 Months	(1)	(68)
12 Months or More	(32)	(48)
Total	(33)	(116)
U.S. Treasury and agency securities
Fair Value
Less Than 12 Months	0	992
12 Months or More	1,742	744
Total	1,742	1,736
Gross Unrealized Losses
Less Than 12 Months	0	(7)
12 Months or More	(6)	(5)
Total	(6)	(12)
Commercial paper
Fair Value
Less Than 12 Months		9,888
12 Months or More		0
Total		9,888
Gross Unrealized Losses
Less Than 12 Months		(5)
12 Months or More		0
Total		(5)
Asset-backed securities
Fair Value
Less Than 12 Months	996	8,499
12 Months or More	3,616	4,758
Total	4,612	13,257
Gross Unrealized Losses
Less Than 12 Months	0	(15)
12 Months or More	(8)	(17)
Total	$ (8)	$ (32)

Marketable Securities and Fai_6

Marketable Securities and Fair Value Measurements - Schedule of Fair Value of Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financial Assets
Marketable Securities	$ 88,784	$ 87,754
Total	122,751	128,375
Level 1
Financial Assets
Total	33,967	40,621
Level 2
Financial Assets
Total	88,784	87,754
Cash
Financial Assets
Cash and Cash Equivalents	32,615	39,113
Cash | Level 1
Financial Assets
Cash and Cash Equivalents	32,615	39,113
Cash equivalents
Financial Assets
Cash and Cash Equivalents	1,352	1,508
Cash equivalents | Level 1
Financial Assets
Cash and Cash Equivalents	1,352	1,508
Certificates of deposit
Financial Assets
Marketable Securities	12,022	11,004
Certificates of deposit | Level 2
Financial Assets
Marketable Securities	12,022	11,004
Corporate securities
Financial Assets
Marketable Securities	48,273	46,337
Corporate securities | Level 2
Financial Assets
Marketable Securities	48,273	46,337
U.S. Treasury and agency securities
Financial Assets
Marketable Securities	1,742	1,736
U.S. Treasury and agency securities | Level 2
Financial Assets
Marketable Securities	1,742	1,736
Commercial paper
Financial Assets
Marketable Securities	11,418	12,323
Commercial paper | Level 2
Financial Assets
Marketable Securities	11,418	12,323
Asset-backed securities
Financial Assets
Marketable Securities	15,329	16,354
Asset-backed securities | Level 2
Financial Assets
Marketable Securities	$ 15,329	$ 16,354

Condensed Consolidated Financ_3

Condensed Consolidated Financial Statement Details - Schedule of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 8,502	$ 7,979
Finished goods	12,450	9,951
Total inventory	$ 20,952	$ 17,930

Condensed Consolidated Financ_4

Condensed Consolidated Financial Statement Details - Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Prepaid expenses	$ 6,675	$ 6,679
Deferred contract acquisition costs	5,711	6,564
Other	4,727	1,419
Total prepaid and other current assets	$ 17,113	$ 14,662

Condensed Consolidated Financ_5

Condensed Consolidated Financial Statement Details - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 58,831	$ 58,851
Less: accumulated depreciation	(51,155)	(51,589)
Property and equipment, net	7,676	7,262
Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	49,230	49,804
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,108	4,088
Furniture and fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	967	967
Leasehold improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,834	3,832
Construction in progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 692	$ 160
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_6

Condensed Consolidated Financial Statement Details - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.2	$ 1.7
Amortization expense related to intangible assets	$ 0.4	$ 0.4
Weighted average useful life of intangible assets	2 years 5 months

Condensed Consolidated Financ_7

Condensed Consolidated Financial Statement Details - Purchased Intangible Assets, net (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	$ 7,986	$ 7,986
Accumulated Amortization	(4,599)	(4,238)
Total	3,387	3,748
Developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	5,050	5,050
Accumulated Amortization	(2,778)	(2,525)
Total	2,272	2,525
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Cost	2,936	2,936
Accumulated Amortization	(1,821)	(1,713)
Total	$ 1,115	$ 1,223

Condensed Consolidated Financ_8

Condensed Consolidated Financial Statement Details - Future Amortization Expense of Acquired Intangibles (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Remainder of 2019	$ 1,082
2020	1,442
2021	863
Total	$ 3,387	$ 3,748

Condensed Consolidated Financ_9

Condensed Consolidated Financial Statement Details - Accrued Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accrued Liabilities, Current [Abstract]
Accrued compensation and benefits	$ 11,605	$ 15,283
Accrued tax liabilities	5,555	4,455
Other	8,276	5,553
Total accrued liabilities	$ 25,436	$ 25,291

Condensed Consolidated Finan_10

Condensed Consolidated Financial Statement Details - Schedule of Deferred Revenue (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 98,569	$ 97,966
Less: current portion	(62,528)	(63,874)
Non-current portion	36,041	34,092
Products
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	5,529	5,216
Services
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 93,040	$ 92,750

Credit Facility (Details)

Credit Facility (Details) - Line of credit	1 Months Ended
	Sep. 30, 2018	Nov. 30, 2016USD ($)	Mar. 31, 2019USD ($)
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) - shares	Jan. 01, 2019	Sep. 30, 2018	Jun. 10, 2015	Oct. 31, 2018	Mar. 31, 2019
2014 Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future grant (in shares)					12,613,705
Expiration period					5 years
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)	3,715,060
2014 Stock Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expiration period					10 years
Vesting period					4 years
2014 Stock Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares reserved for future issuance (in shares)			8,000,000
Percentage of outstanding shares of common stock			5.00%
Voting percentage					10.00%
2014 Stock Incentive Plan | Maximum | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period					4 years
2014 Stock Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock percentage					110.00%
2014 Stock Incentive Plan | Minimum | Non Statutory Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock percentage					100.00%
2014 Stock Incentive Plan | Minimum | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period					1 year
2014 Employee Stock Purchase Plan | ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of eligible compensation		15.00%
Offering period		24 months
Amended 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 eligible compensation				10.00%
Offering period				6 months
Percentage of market value					85.00%
Maximum shares to purchase (in shares)					1,500

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
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 3,896	$ 8,151
Cost of revenue
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	324	893
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,321	2,765
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	1,331	3,382
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	920	1,111
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	184	329
Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,474	2,665
Employee stock purchase rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	238	$ 5,157
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	3 Months Ended
	Mar. 31, 2019USD ($)
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total compensation expense related to unvested awards granted, not yet recognized	$ 28.7
Total compensation expense related to unvested awards granted, not yet recognized weighted-average period for recognition (in years)	2 years 6 months

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, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Number of Shares (thousands)
Outstanding options, Beginning balance (in shares)	4,674
Granted (in shares)	0
Exercised (in shares)	(305)
Canceled (in shares)	(47)
Outstanding options, Ending balance (in shares)	4,322
Vested and exercisable (in shares)	3,855
Weighted-Average Exercise Price
Beginning balance (in dollars per share)	$ 5.19
Granted (in dollars per share)	0
Exercised (in dollars per share)	3.36
Canceled (in dollars per share)	8.10
Ending balance (in dollars per share)	5.28
Vested and exercisable at end of period (in dollars per share)	$ 5.14
Weighted-average remaining contractual term (in years)	4 years 10 months 24 days
Weighted average remaining contractual term, Vested and exercisable at end of period (in years)	4 years 5 months
Aggregate Intrinsic Value	$ 9,498
Aggregate Intrinsic Value, Vested and exercisable at end of period	$ 9,061
Closing price (in dollars per share)	$ 7.09
Intrinsic value of options exercised	$ 1,100	$ 1,100

Equity Incentive Plans and St_7

Equity Incentive Plans and Stock-Based Compensation - Information About Stock Options (Details) - shares	1 Months Ended			3 Months Ended	12 Months Ended
	Oct. 31, 2018	Oct. 31, 2016	Feb. 29, 2016	Mar. 31, 2019	Dec. 31, 2015	Dec. 31, 2014
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
PSUs, February 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)			547,000
Actual performance vesting percentage			80.00%
Vested in period (in shares)				253,203
Forfeited in period (in shares)				200,297
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
PSUs, October 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	464,888
Vested in period (in shares)				0
Tranche One | PSUs, February 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage				80.00%
Tranche One | PSUs, October 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	75.00%
Tranche Two | PSUs, October 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	25.00%

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	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
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)	5,974
Granted (in shares)	248
Released (in shares)	(577)
Canceled (in shares)	(259)
Unvested at end of period (in shares)	5,386
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)	$ 6.51
Granted (in dollars per share)	6.87
Released (in dollars per share)	6.30
Canceled (in dollars per share)	6.72
Unvested at ending of period (in dollars per share)	$ 6.54
Weighted-Average Remaining Vesting Term (years)	1 year 6 months
Fair value of released awards	$ 3.8	$ 4.3

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
	Mar. 31, 2019	Mar. 31, 2018
Stock options, restricted stock units and employee stock purchase rights
Earnings Per Share Diluted [Line Items]
Anti-dilutive securities excluded from computation of diluted net income per share	9,997	10,431

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income tax expense	$ 517	$ 207
Unrecognized tax benefits	$ 4,200		$ 4,200

Geographic Information - Schedu

Geographic Information - Schedule of Total Revenue Based on Customer's Location (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Total revenue	$ 50,290	$ 49,183
United States
Segment Reporting Information [Line Items]
Total revenue	18,100	20,678
Japan
Segment Reporting Information [Line Items]
Total revenue	13,152	13,080
Asia Pacific, excluding Japan
Segment Reporting Information [Line Items]
Total revenue	8,776	7,438
EMEA
Segment Reporting Information [Line Items]
Total revenue	7,229	6,499
Other
Segment Reporting Information [Line Items]
Total revenue	$ 3,033	$ 1,488

Geographic Information - Long L

Geographic Information - Long Lived Assets By Geographic Area (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 13,126	$ 7,262
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	7,652	5,525
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	3,488	1,108
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets	$ 1,986	$ 629

Revenue - Additional Informatio

Revenue - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Jan. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit	$ 284,518,000		$ 272,246,000
Revenue recognized that was included in deferred revenue balance at January 1, 2018	23,700,000	$ 19,500,000
Asset impairment charges for contract assets	0
ASU 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit				$ 12,400,000
Deferred revenue				4,000,000
Deferred commissions asset				$ 8,400,000
Deferred Sales Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred contract acquisition costs	9,000,000
Amortization	2,000,000	$ 1,700,000
Impairment loss of contract acquisition costs	$ 0

Revenue - Contract Balances (De

Revenue - Contract Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 44,802	$ 53,972
Deferred revenue	62,528	63,874
Deferred revenue, non-current	$ 36,041	$ 34,092

Revenue - Remaining Performance

Revenue - Remaining Performance Obligations (Details) $ in Thousands	Mar. 31, 2019USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 98,569
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 62,528
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 29,469
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]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation	$ 6,572
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation period

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) $ in Thousands	May 06, 2019	Mar. 31, 2019
Subsequent Event [Line Items]
Total rent payments due		$ 6,335
Subsequent event
Subsequent Event [Line Items]
Term of lease	7 years 8 months
Rent expense	$ 262
Total rent payments due	$ 26,400