Forescout (FSCT) 10-K 22 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 19, 2018	Dec. 29, 2017
Document and Entity Information [Abstract]
Entity Registrant Name	FORESCOUT TECHNOLOGIES, INC
Entity Central Index Key	1,145,057
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Common Stock, Shares Outstanding		38,367,757
Entity Public Float			$ 493,541,535

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 63,009	$ 79,665
Marketable securities	123,384	0
Accounts receivable	65,428	44,694
Inventory	3,660	890
Prepaid expenses and other current assets	8,655	8,592
Total current assets	264,136	133,841
Property and equipment, net	23,260	24,536
Severance pay deposits	2,118	1,704
Restricted cash	4,146	4,011
Other assets	2,002	3,334
Total assets	295,662	167,426
Current liabilities:
Accounts payable	7,348	5,210
Accrued compensation	25,358	17,286
Accrued expenses	10,023	12,903
Customer deposits	1,008	718
Deferred revenue	98,027	68,844
Notes payable	7,245	7,163
Total current liabilities	149,009	112,124
Warrant liabilities	0	4,874
Deferred revenue - non-current	64,731	40,070
Notes payable - non-current	15,579	22,824
Accrued severance pay liability	2,617	2,033
Other liabilities	9,190	10,244
Total liabilities	241,126	192,169
Commitments and contingencies (Note 5)
Redeemable convertible preferred stock (Note 7)	0	283,854
Stockholders' equity (deficit):
Common stock, $0.001 par value; 43,188,042 and 57,102,290 shares authorized at December 31, 2016 and 2017, respectively; 5,854,147 and 38,121,951 shares issued and outstanding at December 31, 2016 and 2017, respectively.	38	6
Additional paid-in capital	551,986	84,792
Accumulated other comprehensive loss	(112)	0
Accumulated deficit	(497,376)	(393,395)
Total stockholders’ (deficit) equity	54,536	(308,597)
Total liabilities, redeemable convertible preferred stock and stockholders' (deficit) equity	$ 295,662	$ 167,426

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (shares)	57,102,290	43,188,042
Common stock, shares issued (shares)	38,121,951	5,854,147
Common stock, shares outstanding (shares)	38,121,951	5,854,147

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product	$ 121,413	$ 98,655	$ 71,264
Maintenance and professional services	99,458	68,186	54,695
Total revenue	220,871	166,841	125,959
Cost of revenue:
Product	24,098	21,678	16,161
Maintenance and professional services	34,771	26,571	16,961
Total cost of revenue	58,869	48,249	33,122
Total gross profit	162,002	118,592	92,837
Operating expenses:
Research and development	47,435	31,490	17,772
Sales and marketing	151,093	127,815	70,269
General and administrative	51,206	30,731	22,874
Total operating expenses	249,734	190,036	110,915
Loss from operations	(87,732)	(71,444)	(18,078)
Interest expense	(1,223)	(2,577)	(2,745)
Other income (expense), net	316	(607)	(488)
Revaluation of warrant liabilities	(727)	1,104	(5,621)
Loss before income taxes	(89,366)	(73,524)	(26,932)
Income tax provision	1,839	1,250	328
Net loss	(91,205)	(74,774)	(27,260)
Deemed dividend on the conversion of Series G redeemable convertible preferred stock	12,810	0	0
Net loss attributable to common stockholders	$ (104,015)	$ (74,774)	$ (27,260)
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (9.12)	$ (13.33)	$ (6.61)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	11,405,356	5,609,187	4,121,852

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss	$ (91,205)	$ (74,774)	$ (27,260)
Other comprehensive loss, net of tax:
Change in unrealized gains on marketable securities	(112)	0	0
Comprehensive loss	$ (91,317)	$ (74,774)	$ (27,260)

Consolidated Statements of Rede

Consolidated Statements of Redeemable Convertible Preferred Stock and Stockholders' (Deficit) Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit
Redeemable convertible preferred stock, beginning balance (in shares) at Dec. 31, 2014	14,826,324
Redeemable convertible preferred stock, beginning balance at Dec. 31, 2014	$ 200,501
Increase (Decrease) in Temporary Equity [Roll Forward]
Net proceeds from issuance of Series G redeemable convertible preferred stock (in shares)	3,176,009
Net proceeds from issuance of Series G redeemable convertible preferred stock	$ 73,798
Exercise of warrants on redeemable convertible preferred stock (in shares)	298,050
Exercise of warrants on redeemable convertible preferred stock	$ 5,614
Redeemable convertible preferred stock, ending balance (in shares) at Dec. 31, 2015	18,300,383
Redeemable convertible preferred stock, ending balance at Dec. 31, 2015	$ 279,913
Stockholders' (deficit) equity, beginning balance (in shares) at Dec. 31, 2014		2,757,911
Stockholders' (deficit) equity, beginning balance at Dec. 31, 2014	(243,685)	$ 3	$ 47,673	$ 0	$ (291,361)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on marketable securities	0
Stock-based compensation	8,712		8,712
Issuance of common stock upon exercise of stock options, net of unvested portion (in shares)		2,169,318
Issuance of common stock upon exercise of stock options, net of unvested portion	8,349	$ 2	8,347
Vesting of early exercised stock options (in shares)		139,848
Vesting of early exercised stock options	1,082		1,082
Net loss	(27,260)				(27,260)
Stockholders' (deficit) equity, ending balance (in shares) at Dec. 31, 2015		5,067,077
Stockholders' (deficit) equity, ending balance at Dec. 31, 2015	$ (252,802)	$ 5	65,814	0	(318,621)
Increase (Decrease) in Temporary Equity [Roll Forward]
Net proceeds from issuance of Series G redeemable convertible preferred stock (in shares)	168,534
Net proceeds from issuance of Series G redeemable convertible preferred stock	$ 3,941
Redeemable convertible preferred stock, ending balance (in shares) at Dec. 31, 2016	18,468,917
Redeemable convertible preferred stock, ending balance at Dec. 31, 2016	$ 283,854
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on marketable securities	0
Stock-based compensation	16,834		16,834
Issuance of common stock upon vesting of RSUs (in shares)		212,903
Issuance of common stock upon vesting of RSUs	$ 0
Issuance of common stock upon exercise of stock options, net of unvested portion (in shares)	431,095	431,095
Issuance of common stock upon exercise of stock options, net of unvested portion	$ 1,071	$ 1	1,070
Vesting of early exercised stock options (in shares)		143,072
Vesting of early exercised stock options	1,074		1,074
Net loss	$ (74,774)				(74,774)
Stockholders' (deficit) equity, ending balance (in shares) at Dec. 31, 2016	5,854,147	5,854,147
Stockholders' (deficit) equity, ending balance at Dec. 31, 2016	$ (308,597)	$ 6	84,792	0	(393,395)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of accounting change	$ 34				34
Exercise of warrants on redeemable convertible preferred stock (in shares)	55,987
Conversion of redeemable convertible preferred stock to common stock in connection with the initial public offering (in shares)	(18,524,904)
Conversion of redeemable convertible preferred stock to common stock in connection with the initial public offering	$ (283,854)
Redeemable convertible preferred stock, ending balance (in shares) at Dec. 31, 2017	0
Redeemable convertible preferred stock, ending balance at Dec. 31, 2017	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss on marketable securities	(112)			(112)
Stock-based compensation	$ 42,562		42,562
Issuance of common stock upon exercise of stock options, net of unvested portion (in shares)	305,863	305,863
Issuance of common stock upon exercise of stock options, net of unvested portion	$ 1,626		1,626
Issuance of common stock in connection with initial public offering, net of offering costs (in shares)		6,072,000
Issuance of common stock in connection with initial public offering, net of offering costs	119,684	$ 6	119,678
Conversion of redeemable convertible preferred stock to common stock in connection with the initial public offering (in shares)		24,844,349
Conversion of redeemable convertible preferred stock to common stock in connection with the initial public offering	283,854	$ 25	283,829
Conversion of preferred stock warrants to common stock warrants in connection with initial public offering	4,173		4,173
Vesting of early exercised stock options (in shares)		183,487
Vesting of early exercised stock options	1,089		1,089
Shares issued for warrant exercise (in shares)		279,851
Shares issued for preferred stock warrant exercise	1,428		1,428
Deemed dividend on the conversion of Series G redeemable convertible preferred stock (in shares)		582,254
Deemed dividend on the conversion of Series G redeemable convertible preferred stock	0	$ 1	12,809		(12,810)
Net loss	$ (91,205)				(91,205)
Stockholders' (deficit) equity, ending balance (in shares) at Dec. 31, 2017	38,121,951	38,121,951
Stockholders' (deficit) equity, ending balance at Dec. 31, 2017	$ 54,536	$ 38	$ 551,986	$ (112)	$ (497,376)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities
Net loss	$ (91,205)	$ (74,774)	$ (27,260)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities
Stock-based compensation	42,596	16,834	8,712
Depreciation	6,068	3,610	1,788
Amortization of discount on debt and interest income	(127)	694	651
Revaluation of warrant liabilities	727	(1,104)	5,621
Allowance for doubtful accounts	0	0	(346)
Changes in operating assets and liabilities
Accounts receivable	(20,734)	(15,469)	(6,533)
Inventory	(2,719)	(450)	(55)
Deferred cost of revenue	257	(154)	2,492
Prepaid expenses and other current assets	(320)	(4,878)	(1,017)
Other assets	(535)	(1,767)	(212)
Accounts payable	1,734	596	29
Accrued compensation	8,072	4,134	819
Accrued expenses	(889)	3,145	2,201
Customer deposits	290	(1,100)	(712)
Deferred revenue	53,844	25,455	17,003
Severance pay, net	170	164	23
Other liabilities	36	6,773	193
Net cash provided by (used in) operating activities	(2,735)	(38,291)	3,397
Cash flows from investing activities
Purchases of property and equipment	(4,517)	(22,006)	(2,757)
Purchases of marketable securities	(123,032)	(23,983)	0
Proceeds from maturities of marketable securities	0	12,000	0
Proceeds from sales of marketable securities	0	11,979	0
Change in restricted cash	(136)	(189)	(3,308)
Net cash used in investing activities	(127,685)	(22,199)	(6,065)
Cash flows from financing activities
Net borrowings of notes payable	0	29,977	0
Repayments of notes payable	(7,500)	(20,130)	(172)
Payment of accrued success fees	(350)	0	0
Net proceeds from issuance of redeemable convertible preferred stock	0	2,399	75,340
Proceeds from issuance of redeemable convertible preferred stock upon exercise of warrants	0	0	90
Proceeds from exercise of stock options	1,626	1,071	11,784
Repurchase of unvested common stock	0	0	(149)
Payments of deferred offering costs	(4,245)	(8)	0
Proceeds from initial public offering, net of underwriting discounts and commissions	124,233	0	0
Net cash provided by financing activities	113,764	13,309	86,893
Net change in cash and cash equivalents for period	(16,656)	(47,181)	84,225
Cash and cash equivalents at beginning of period	79,665	126,846	42,621
Cash and cash equivalents at end of period	63,009	79,665	126,846
Supplemental disclosure of cash flow information:
Cash paid for income taxes	1,634	1,012	310
Cash paid for interest	819	2,014	2,011
Noncash disclosure of investing and financing activities:
Change in liability for early exercise of stock options, net of vested portion	1,089	1,075	(2,203)
Costs related to issuance of redeemable convertible preferred stock in accrued expenses	0	0	1,542
Leasehold improvements paid by lessor	0	338	238
Purchases of property and equipment recorded in accounts payable and accrued expenses	448	547	107
Deferred offering costs included in accrued expenses	296	1,435	0
Unrealized loss on marketable securities	112	0	0
Conversion of preferred stock warrants to common stock warrants in connection with initial public offering	4,173	0	0
Cashless exercise of preferred stock warrants	$ 1,428	$ 0	$ 0

Description of Business and Sum

Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business and Summary of Significant Accounting Policies	Description of Business and Summary of Significant Accounting Policies Company and Background ForeScout Technologies, Inc. (the “Company”) was incorporated in the State of Delaware and commenced operations in April 2000. The Company provides an agentless approach to network security to protect organizations against the emerging threats that exploit billions of Internet of Things (“IoT”) devices connected to an organization’s networks. The Company offers its solution across three products: (i) ForeScout CounterACT ® , (ii) ForeScout CounterACT Enterprise Manager and (iii) ForeScout Extended Modules. The Company’s CounterACT product provides visibility and policy-based mitigation of security issues. The Company’s CounterACT Enterprise Manager is a centralized security management solution for global control of all CounterACT products. The Company’s Extended Modules expand CounterACT’s see and control capabilities by sharing contextual device data with third-party systems and by automating policy enforcement across those disparate systems. The Company sells its products, maintenance, and professional services to end-customers through distributors and resellers, who are supported by the Company’s sales and marketing organization, and to a lesser extent directly to end-customers. Initial Public Offering On October 31, 2017 , the Company closed its initial public offering (“IPO”), in which it issued and sold 6,072,000 shares of common stock inclusive of the underwriters’ option to purchase additional shares that was exercised in full. The price per share to the public was $22.00 . The Company received aggregate proceeds of $124.2 million from the IPO, net of underwriters’ discounts and commissions, and before deducting offering costs of approximately $4.5 million . Upon the closing of the IPO, all shares of the Company's outstanding redeemable convertible preferred stock automatically converted into 25,370,616 shares of common stock. Basis of Presentation The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The Company’s consolidated financial statements include the results of ForeScout Technologies, Inc. and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make use of estimates and assumptions that affect the reported amounts in the consolidated financial statements and accompanying notes. These estimates form the basis of judgments made about carrying values of assets and liabilities, which are not readily apparent from other sources. The areas where management has made estimates requiring judgment include, but are not limited to, the allocation of revenue in multiple element arrangements, sales return reserve, accruals, stock-based compensation including the fair value of common stock, redeemable convertible preferred stock warrant liabilities, and provision for income taxes, including related reserves. Actual results could differ materially from those estimates. Reverse Stock Split On October 16, 2017, the Company amended its amended and restated certificate of incorporation to effect a two-to-one reverse stock split of its common stock and convertible preferred stock (the “Reverse Stock Split”). Upon the filing of the amended and restated certificate of incorporation in the state of Delaware, (i) each two shares of outstanding convertible preferred stock and each two shares of outstanding common stock were exchanged and combined into one share of convertible preferred stock and one share of common stock, respectively; (ii) the number of shares of common stock issuable under each outstanding option to purchase common stock and issuable upon vesting under each restricted stock unit was proportionately reduced on a two -to-one basis; (iii) the exercise price of each outstanding option to purchase common stock was proportionately increased on a two -to-one basis; (iv) the number of shares of convertible preferred stock issuable under outstanding warrants was proportionally reduced on a two -to-one basis and the exercise price of such warrants was proportionally increased on a two -to-one basis; and (v) corresponding adjustments in the per share conversion prices, dividend rates and liquidation preferences of the convertible preferred stock were made on a two -to-one basis. Accordingly, all share and per share information presented in the consolidated financial statements herein, and notes thereto, have been retroactively adjusted to reflect the Reverse Stock Split. Segment information The chief operating decision maker (“CODM”) is the Chief Executive Officer who reviews financial information presented on a consolidated basis. The Company has one business activity and there are no segment managers who are held accountable by the CODM for operations, operating results and planning for levels or components below the consolidated level. The Company operates in one segment. Concentrations Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, marketable securities, accounts receivable, severance pay deposits, and restricted cash. The Company maintains all of its cash and cash equivalents in interest-bearing bank accounts and money market accounts. Management believes that the financial institutions that hold the Company’s cash and cash equivalents are financially sound and exposed to minimal credit risk. Deposits held with banks generally exceed the amount of insurance provided on such deposits. Accounts receivable are primarily derived from the Company’s customers, including distributors and resellers representing various geographical locations. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable, and, if necessary, an allowance for doubtful accounts is maintained for estimated potential credit losses. As of December 31, 2016 and 2017 , four customers represented 20% , 17% , 16% , and 12% of total accounts receivable, and two customers represented 32% and 17% of total accounts receivable, respectively. For the year ended December 31, 2015 , three customers represented 14% , 11% , and 10% of the Company’s total revenue. For the year ended December 31, 2016 , three customers represented 24% , 14% , and 13% of the Company’s total revenue. For the year ended December 31, 2017 , three customers represented 30% , 21% , and 17% of the Company’s total revenue. The Company purchases its hardware appliances from one contract manufacturer that assembles all of its products. Foreign Currency The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Monetary assets and liabilities are remeasured using the current exchange rate at the balance sheet date. Non-monetary assets and liabilities and capital accounts are remeasured using historical exchange rates. Revenue and expenses have been remeasured using the average exchange rates in effect during each period. Foreign currency remeasurement gains and losses are recorded in other expense, net. The Company recognized net foreign currency remeasurement losses of $0.4 million , $0.9 million , and $0.1 million , respectively, for the years ended December 31, 2015 , 2016 and 2017 . Cash and Cash Equivalents The Company considers all highly liquid investments held at financial institutions with original maturities of three months or less at date of purchase to be cash equivalents. Cash and cash equivalents are stated at cost, which approximates fair value. Marketable Securities The Company’s marketable securities consist primarily of commercial paper, corporate debt securities, and U.S. government agency securities. The Company’s marketable securities are classified as available-for-sale and are reported at fair value. The Company determines any realized gains or losses on the sale of available-for-sale securities on a specific identification method, and such gains and losses are recorded as a component of other income (expense), net on our consolidated statements of operations. Unrealized gains and losses of the available-for-sale securities are excluded from earnings and reported as a component of accumulated other comprehensive income (loss). The Company has classified and accounted for its marketable securities as available-for-sale. After consideration of the Company’s risk versus reward objectives, as well as the Company’s liquidity requirements, the Company may sell these securities prior to their stated maturities. As the Company views these securities as available to support current operations, the Company classifies highly liquid securities with maturities beyond 12 months as current assets under the caption marketable securities in the Consolidated Balance Sheets. Marketable securities are considered impaired when a decline in fair value is judged to be other-than-temporary. The Company considers available quantitative and qualitative evidence in evaluating potential impairment of the marketable securities on a quarterly basis. If the cost of an individual investment exceeds its fair value, the Company evaluates, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and the Company’s intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, the Company will record an impairment charge and establish a new cost basis in the investment. As of December 31, 2017 , the Company did not consider any of its marketable securities to be other-than-temporarily impaired. Restricted Cash As of December 31, 2016 and 2017 , the Company had restricted cash of $0.2 million , and $0.2 million recorded as prepaid expenses and other current assets, respectively, and $4.0 million , and $4.1 million recorded as non-current restricted cash, respectively. Restricted cash primarily consists of letters of credit issued as security deposits required for facility leases. Accounts Receivable Trade accounts receivable are recorded at the invoiced amount, net of allowances for doubtful accounts. The Company assesses its trade accounts receivable for doubtful accounts based on the collectability of accounts. Management regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice, each customer’s expected ability to pay, and the collection history with each customer, to determine whether a specific allowance is appropriate. Accounts receivable that are deemed uncollectible are charged against the allowance for doubtful accounts. Based on management’s assessment of its trade accounts receivable, the Company did not record an allowance for doubtful accounts as of December 31, 2016 and 2017 . Inventory Inventory primarily consists of finished goods hardware appliances and is stated at the lower of cost or market determined using the specific identification method. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory. There were no material inventory write-downs for the years ended December 31, 2015 , 2016 , and 2017 . Property and Equipment Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years. Demonstration units are not resold after use and are depreciated over the estimated useful life of three years or less. Leasehold improvements are depreciated over the shorter of the estimated useful lives of the improvements or the remaining lease term. Impairment of Long-Lived Assets Management reviews long-lived assets for events and changes in circumstances that may indicate that carrying amounts of long-lived assets, including property and equipment, may not be recoverable. When such events or circumstances occur, recoverability of these assets is measured by a comparison of the carrying value to the future undiscounted cash flows the assets are expected to generate. If long-lived assets are considered to be impaired, the impairment to be recognized would equal the amount by which the carrying value of the asset exceeds its fair market value. To date, the Company has not recorded any significant impairment to its long-lived assets. Deferred Offering Costs Deferred offering costs consisted of fees and expenses incurred in connection with the sale of the Company’s common stock in its IPO, including direct incremental legal, consulting, accounting fees, and other IPO-related costs. Upon completion of the Company’s IPO, these deferred offering costs were reclassified to stockholders’ deficit and offset against the proceeds of the offering. As of December 31, 2016 , deferred offering costs of $1.4 million were included within other assets on the consolidated balance sheets. Total deferred offering costs recognized through the completion of the IPO and reclassified to stockholders' deficit and offset against the IPO proceeds were $4.5 million . Product Warranty The Company provides a standard 90 day warranty on its hardware and software products. The Company also offers its customers post-contract support (“PCS”), which includes a warranty of between one to five -years on hardware. The Company will also provide its customers software releases or updates during the PCS term. The Company accrues for estimated standard warranty costs for those customers that do not purchase PCS at the time of product shipment. These potential warranty claims are accrued as a component of product cost of revenue based on historical experience and other data, which is reviewed periodically for adequacy. Warranty costs associated with PCS are expensed as incurred. To date, the Company has not incurred nor accrued any significant costs associated with product warranty. Contract Manufacturer Liabilities Manufacturing, repair, and supply chain management operations are outsourced to a third party contract manufacturer. These costs are a significant portion of product cost of revenue. Although the Company is contractually obligated to purchase manufactured products, the Company generally does not own the manufactured products as product title transfers from the contract manufacturer to the Company and immediately to the customer upon shipment. The contract manufacturer assembles the Company’s products using design specifications, quality assurance programs, and standards that the Company establishes. Components are procured and assembled based on the Company’s demand forecasts. These forecasts represent management’s best estimates of future demand for the products based upon historical trends and analysis from sales and operations functions as adjusted for overall market conditions. The Company accrues for costs for contractual manufacturing commitments in excess of its forecasted demand, including costs incurred for excess components or for the carrying costs incurred by the contract manufacturer. To date, the Company has not accrued any significant contract manufacturer liabilities. Redeemable Convertible Preferred and Common Stock Warrant Liabilities Upon completion of the Company's IPO in October 2017, there were no freestanding warrants to purchase shares of convertible preferred stock. As such, no preferred stock warrant liability remained outstanding after the IPO. Before the Company's IPO, freestanding warrants related to shares that are redeemable or contingently redeemable were classified as a liability in the Company’s consolidated balance sheet. The convertible preferred stock warrants were subject to re-measurement at each balance sheet date, and any change in fair value was recognized in the consolidated statements of operations. The Company adjusted the redeemable convertible preferred stock warrant liability to the estimated fair value of the warrants until either the exercise or the completion of the Company’s IPO, at which time the redeemable convertible preferred stock issuable upon exercise of the warrants became warrants to purchase common stock and the related liability was reclassified to additional paid-in capital in stockholders' equity (deficit). At December 31, 2016 , common stock warrants to purchase 233,023 shares of the Company’s common stock at a weighted-average exercise price of $6.62 per share were outstanding. During the year ended December 31, 2017 , 149,786 common stock warrants of the 233,023 common stock warrants were exercised. In lieu of payment of the aggregate warrant price, the warrant holders elected a "cashless exercise", whereby a portion of the shares equal to the aggregate warrant price were withheld. The average fair market value at the time exercise was $25.28 , which resulted in 111,147 shares being issued by the Company. As of December 31, 2017 , 83,237 common stock warrants remained outstanding and exercisable. Severance Pay Deposits and Accrued Severance Pay Liability The Company records a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. Under Israeli law and labor agreements, the Company is required to make severance and pension payments to retired or dismissed employees and to employees leaving employment in certain other circumstances. Liabilities for severance pay are calculated pursuant to Israeli severance pay law using the most recent monthly salary for the employees, multiplied by the number of years of employment, and are included in accrued severance pay liability in the Company’s balance sheets. The Company’s liability at each respective balance sheet date for its Israeli employees is fully accrued in the accompanying consolidated financial statements. The severance liability is funded through monthly deposits to the employee’s pension and management insurance carriers. The fair value of this deposit is recorded in severance pay deposits in the Company’s consolidated balance sheets. Revenue Recognition The Company derives its revenue from sales of products and associated maintenance and professional services. The Company’s CounterACT and Enterprise Manager products are sold as hardware appliances embedded with the Company’s software, or Physical Appliances, or as software only, or Virtual Appliances. The Company also recently started offering, in limited quantities to a small number of large enterprises, CounterACT and Enterprise Manager together as a software only license (“Enterprise License Software”). The Company’s Enterprise License Software is either sold with separate hardware or without hardware, depending on the end-customer’s selection. The Company’s portfolio of Extended Modules are sold as software add-ons to CounterACT and Enterprise Manager. The Company accounts for the sale of Physical Appliances, and Enterprise License Software sold with separate hardware (“Hardware Products”) pursuant to Financial Accounting Standards Board, or FASB, Accounting Standard Codification Topic (“ASC”) 605-25, Revenue Recognition: Multiple Element Arrangements. The Company accounts for the sale of Virtual Appliances, Enterprise License Software sold without hardware, and Extended Modules as software deliverables (“Software Products”) pursuant to FASB, ASC Topic 985-605, Software Revenue Recognition. All of the Company’s products are sold with a perpetual license. The Company recognizes revenue when all of the following criteria are met: • Persuasive Evidence of an Arrangement Exists. The Company relies upon binding sales agreements and/or purchase orders to provide evidence of an arrangement. • Delivery has Occurred. The Company uses shipping documents and/or electronic transmissions to evidence delivery of products. • The Fee is Fixed or Determinable. The Company determines whether the fee is fixed or determinable based on the payment terms associated with the transaction. • Collectability is Reasonably Assured. The Company evaluates collectability based on credit analysis and payment history. Payments from the Company’s distributors and resellers are not contingent on the distributors’ and resellers’ success in sales to end-customers. The Company’s distributors and resellers do not stock hardware appliances and have no stock rotation rights. Most of the Company’s sales, other than renewals of support and maintenance, are multiple element arrangements with a combination of Physical Appliances, Virtual Appliances, Extended Modules, Enterprise License Software and hardware sold separately, support and maintenance and professional services. For multiple element arrangements, the arrangement consideration is allocated to software deliverables as a group and non-software deliverables as a second group based on a relative selling price hierarchy. The relative selling price hierarchy is based on: (i) vendor-specific objective evidence of fair value (“VSOE”) if available, (ii) third-party evidence of selling price (“TPE”) if VSOE is not available, or (iii) best estimate of the selling price (“BESP”) if neither VSOE nor TPE is available. Hardware Product revenue is recognized at the time of delivery, provided that all other revenue recognition criteria have been met. Software Product revenue is recognized at the time of delivery if VSOE is established for all undelivered related items. If VSOE does not exist for one or more undelivered items, revenue from the software portion of the arrangement is deferred until the delivery of all items has begun and is then recognized ratably over the remaining related support and maintenance service period. Support and maintenance revenue is generally recognized ratably over the contractual service period, which is typically one to three years , but can be up to five years . Professional services revenue is generally recognized as the services are rendered. For Hardware Products, the Company determined that VSOE and TPE cannot be established. As a result, the Company uses BESP to determine the relative selling price at which a transaction would take place if the hardware product was sold on a stand-alone basis. For Hardware Product related maintenance and professional services, the Company uses either VSOE or BESP when VSOE and TPE cannot be established. In determining the BESP for a product or service, the Company considers historical data including, but not limited to, product family, pricing practices, standalone sales, the nature and size of the customer, contractually stated prices, and geographical region. The Company limits the amount of revenue recognized for delivered elements to an amount that is not contingent upon future delivery of additional products or services or meeting of any specified performance conditions. In multiple-element arrangements that include software, revenue is allocated to each separate unit of accounting for the non-software deliverables, as well as the software deliverables as a group, using the relative estimated selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. The arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable separately using the residual method based on the fair value of each of the undelivered deliverables, using VSOE. The Company typically determines VSOE based on its normal pricing and discounting practices for the specific service when sold separately. The Company establishes VSOE on software related support and maintenance using the bell-shaped curve approach. Under this approach, the Company concludes that VSOE exists if a substantial majority of recent stand-alone renewal transactions are priced within a narrow range. For Enterprise License Software, the Company established VSOE on support and maintenance prior to the occurrence of actual renewals, based on management’s ability to establish support and maintenance renewal rates. The Company ensures that such established VSOE is supported by contractually stated renewal rates. Beginning on January 1, 2016, the Company has established VSOE for professional services, and support and maintenance on Software Products, except Extended Modules. Revenue is reported net of sales taxes. Sales commissions and other incremental costs to acquire contracts are expensed to sales and marketing expense as incurred. Deferred Revenue and Deferred Cost of Revenue After receipt of a customer order, any amounts billed in excess of revenue recognized are recorded as deferred revenue. Deferred revenue consists of amounts that have been invoiced but that have not been recognized as revenue. Deferred revenue that is expected to be recognized within the succeeding 12 month period is recorded as current deferred revenue and the remaining amount is recorded as non-current deferred revenue. Deferred cost of revenue includes direct and incremental costs related to product sales provided for contracts under which revenue has been deferred as the earnings process has not been completed. Deferred cost of revenue that is expected to be realized within the succeeding 12 month period is recorded as current deferred cost of revenue and the remaining amount is recorded as non-current other assets. Customer Deposits As of December 31, 2016 and 2017 , the Company had customer deposits of $0.7 million , and $1.0 million , respectively. Customer deposits represents amounts received from customers in advance for future orders of goods or services. Software Development Costs Software development costs are not capitalized as the software development process is essentially completed concurrent with the establishment of technological feasibility. As such, all software development costs are expensed as incurred and included in research and development expense in the accompanying consolidated statements of operations. Advertising Costs Advertising costs include costs incurred on print, broadcast, and online advertising. Advertising costs are expensed as incurred and included in sales and marketing expense in the accompanying consolidated statements of operations. The Company recognized advertising expenses of $7,000 , $291,000 , and $430,000 for the years ended December 31, 2015 , 2016 and 2017 , respectively. Stock-Based Compensation Stock-based compensation for employees is measured based on the grant date fair value of the award and is expensed over the requisite service period, which is generally the vesting period. The Company accounts for stock-based compensation to non-employees using the fair value approach. Equity awards to non-employees are subject to remeasurement at each reporting period over their vesting terms. The fair value of option awards is determined on the date of grant using the Black-Scholes option pricing model. In applying the Black-Scholes option pricing model, the Company’s determination of the fair value of the option award on the grant date is affected by the Company’s estimated fair value of the underlying common stock, as well as assumptions relating to subjective variables. These variables include the expected term of the award, the expected volatility of the common stock price, the risk-free interest rate, and the expected dividend yield of common stock. The fair value of restricted stock units (“RSUs”) is determined on the date of grant using the Company’s estimated fair value of the underlying common stock. Prior to January 1, 2017, for awards with a service condition only, the Company recognized stock-based compensation expense over the service period on a straight-line basis, net of forfeitures. For awards with both a service and performance condition, stock-based compensation expense is recognized over the service period using an accelerated attribution method once the performance conditions become probable. Beginning January 1, 2017 with the adoption of ASU 2016-09, the Company elected to recognize forfeitures as they occur, and no longer estimates a forfeiture rate when calculating the stock-based compensation for equity awards. Stock-based compensation for the years ended December 31, 2015 and 2016 was calculated using an estimated forfeiture rate based on an analysis of the Company’s actual historical forfeitures. Income Taxes Deferred income taxes are recognized using the asset and liability method, whereby deferred tax assets and liabilities are recognized for the expected future tax consequences attributable to differences between the Company’s (1) financial statement carrying amounts and their respective tax bases and (2) operating loss and tax credit carryforwards. Valuation allowances are provided when the expected realization of tax assets does not meet a more-likely-than-not criterion. Due to the Company’s lack of earnings history, the U.S. net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes tax benefits from uncertain tax positions if it is more likely than not that the tax position will be sustained upon examination by a taxing authority based on the technical merits of the position. The tax benefits recognized from such positions are measured based on the largest benefit that has a greater than 50% likelihood to be realized upon settlement. The Company recognizes accrued interest and penalties related to unrecognized tax benefits in income tax expense in the accompanying consolidated statements of operations, when and if incurred. On December 22, 2017, the President of the United States signed the Tax Cuts and Jobs Act (the “Act”) into law. The legislation significantly changes U.S. tax law by, among other things, lowering corporate income tax rates, implementing a territorial tax system and imposing a mandatory repatriation tax on earnings of foreign subsidiaries. The Tax Reform Act permanently reduces the U.S. corporate income tax rate from a maximum of 35% to a flat 21% rate, effective January 1, 2018. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09 (Topic 606), Revenue from Contracts with Customers (“ASU 2014-09”), related to revenue from contracts with customers, which, along with amendments issued in 2015 and 2016, will supersede nearly all current GAAP guidance on this topic and eliminate industry-specific guidance. Under the new standard, revenue is recognized when a customer obtains control of promised goods or services and is recognized in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (“full retrospective method,”) or retrospectively with the cumulative effect of applying the guidance recognized in retained earnings as of the date of adoption (“modified retrospective method”). The Company will adopt the new standard using the full retrospective method effective January 1, 2018. To date, the Company has evaluated the impacts of adoption of the new standard on its accounting policies, processes, and system requirements and has assigned internal resources, in addition to the engagement of third party service providers, to assist in the evaluation. The most significant impact relates to the accounting for Software Products as VSOE for support and maintenance on Software Products prior to January 1, 2016 was not established, and recorded all Software Product related revenue ratably over the contractually committed support and maintenance period. Under the new standard the requirement to have VSOE for undelivered elements is eliminated and an entity may be required to recognize Software Product revenue at the time of delivery, and any related professional services revenue as services are provided to the customers. The Company expects revenue allocated from future deliverables (primarily support and maintenance) to Physical Appliances to be recognized upon delivery under the new guidance when the standalone selling price is different from the contract price. Currently, such differences are recognized over the contractual support and maintenance period. Additionally, the new standard requires the capitalization of costs

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements Financial assets and liabilities are recorded at fair value on the consolidated balance sheets and are categorized based upon the level of judgment associated with inputs used to measure their fair value. Fair value reflects the price that would be received on the sale of an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining fair value measurements, the Company considers the principal or most advantageous market and also market-based risk. The accounting guidance for fair value measurements requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The accounting guidance also establishes a fair value hierarchy based on the independence of the source and objective evidence of the inputs used. There are three fair value hierarchies based upon the level of inputs that are significant to fair value measurement: • Level 1 —Observable inputs that reflect quoted prices in active markets for identical assets or liabilities. • Level 2 —Observable inputs that reflect quoted prices for identical assets and liabilities in markets that are not active, quoted prices for similar assets or liabilities in active markets, inputs other than quoted prices that are observable for the assets or liabilities, or inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 —Inputs that are generally unobservable and are supported by little or no market activity, and typically reflect management’s estimate of assumptions that market participants would use in pricing the asset or liability. There have been no transfers between fair value measurement levels during the periods presented. The following table presents the fair value of the Company’s financial assets and liabilities according to the fair value hierarchy (in thousands): December 31, 2016 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial Assets Cash and cash equivalents: Cash $ 42,499 $ — $ — $ 24,526 $ — $ — Money market accounts 37,166 — — 38,483 — — Total cash and cash equivalents 79,665 — — 63,009 — — Marketable securities: Commercial paper — — — — 40,610 — Corporate debt securities — — — — 58,948 — U.S. government securities — — — — 23,826 — Total marketable securities — — — — 123,384 — Restricted cash 4,212 — — 4,348 — — Total financial assets $ 83,877 $ — $ — $ 67,357 $ 123,384 $ — Financial Liabilities Warrant liabilities $ — $ — $ 4,874 $ — $ — $ — The following table presents the summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows (in thousands): Level 3 Balance as of December 31, 2015 $ 5,978 Revaluation of warrant liabilities (1,104 ) Balance as of December 31, 2016 4,874 Revaluation of warrant liabilities 727 Reclassification of preferred stock warrants to common stock warrants upon IPO (4,173 ) Exercise of preferred stock warrants (1,428 ) Balance as of December 31, 2017 $ —

Marketable Securities

Marketable Securities	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	The following table summarizes the unrealized losses and fair value of the Company’s marketable securities as of December 31, 2017 (in thousands): December 31, 2017 Amortized Cost Unrealized Losses Fair Value Marketable securities: Available-for-sale: Commercial paper $ 40,610 $ — $ 40,610 Corporate debt securities 59,031 (83 ) 58,948 U.S. government securities 23,855 (29 ) 23,826 Total marketable securities $ 123,496 $ (112 ) $ 123,384 The following table summarizes the amortized cost and fair value of the Company’s available-for-sale securities as of December 31, 2017 , by the contractual maturity date (in thousands): December 31, 2017 Amortized Cost Fair Value Due within one year $ 83,419 $ 83,374 Due between one and five years 40,077 40,010 Total $ 123,496 $ 123,384 For individual marketable securities that have been in a continuous unrealized loss position, the fair value and gross unrealized loss for these securities aggregated by investment category and length of time in an unrealized position are presented in the following tables (in thousands): December 31, 2017 Less Than 12 Months Greater Than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate debt securities $ 58,581 $ (83 ) $ — $ — $ 58,581 $ (83 ) U.S. government securities 23,771 (29 ) — — 23,771 (29 ) Total $ 82,352 $ (112 ) $ — $ — $ 82,352 $ (112 ) Unrealized losses related to these marketable securities are due to interest rate fluctuations as opposed to credit quality. In addition, the Company does not intend to sell and it is not likely that the Company would be required to sell these marketable securities before recovery of their amortized cost basis, which may be at maturity. As a result, there is no other-than-temporary impairments for these marketable securities at December 31, 2017 .

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2016 2017 Leasehold improvements $ 18,158 $ 18,617 Computer, equipment and software 7,246 9,835 Furniture and fixtures 3,609 3,577 Demonstration units 1,824 2,528 Construction in progress 111 14 Total property and equipment 30,948 34,571 Less: accumulated depreciation (6,412 ) (11,311 ) Total property and equipment, net $ 24,536 $ 23,260 Depreciation expense related to property and equipment for the years ended December 31, 2015 , 2016 , and 2017 was approximately $1.8 million , $3.6 million and $6.1 million , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company leases office space under various non-cancelable operating leases, which expire through the year ending October 31, 2026. The facility lease agreements include rent holidays and generally provide for rental payments on a graduated basis. The agreements also generally provide for options to renew, which could increase future minimum lease payments if exercised. Lease renewals are not included in the lease term unless the renewals are reasonably assured at lease inception. Rent expense is recognized on a straight-line basis over the lease term. The Company records the difference between cash rent payments and the recognition of rent expense as deferred rent in the consolidated balance sheets. In October 2015, the Company entered into an 11 year lease agreement for corporate office space in San Jose, California. This lease allows for one five -year option to extend the lease term. This option to extend was not assumed in the determination of the lease term as the extension is not reasonably assured at the inception of the lease. This lease contains an incentive for tenant improvements, in addition to a one year rent holiday and escalating rent payments. Consistent with the Company’s other operating leases, rent expense begins on the date legal right to use and control the leased space occurs. As of December 31, 2017 , approximately $15.7 million has been incurred related to the build-out of the Company’s new headquarters and included in leasehold improvements. This lease contains an incentive for tenant improvements of up to $4.8 million , of which the entire $4.8 million was approved and recognized as a reduction of rent expense on a straight-line basis over the term of the lease. As of December 31, 2017 , the future minimum lease payments by fiscal year under non-cancelable leases are as follows (in thousands): Years Ending December 31, Operating 2018 $ 6,100 2019 4,882 2020 3,255 2021 3,356 2022 3,460 2023 and thereafter 14,254 Total $ 35,307 Rent expense was approximately $2.4 million , $5.3 million , and $5.6 million for the years ended December 31, 2015 , 2016 , 2017 , respectively. Contract Manufacturer Commitments As of December 31, 2017 , the Company had contract manufacturer commitments of $6.0 million to purchase components and products from the Company’s third party contract manufacturer. The contract manufacturer commitments result from the Company’s contractual obligation to order or build inventory in advance of anticipated sales. Purchase Obligations As of December 31, 2017 , the Company had purchase obligations of $2.6 million primarily related to non-cancelable license obligations for software licenses. Litigation The Company is a party to various legal proceedings and claims which arise in the ordinary course of business. The Company records a liability when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. If the Company determines that a loss is possible and a range of the loss can be reasonably estimated, the range of the possible loss is disclosed. On October 24, 2017, Network Security Technologies, LLC, or NST, filed a lawsuit against the Company in the United States District Court for the District of Delaware, alleging that the Company infringe U.S. Patent Nos. 8,234,705 and 9,516,048 and is seeking compensatory damages and attorneys’ fees. The Company believed it had meritorious defenses and intended to vigorously defend the claims against the Company. Subsequently, on February 1, 2018, NST filed a notice of voluntary dismissal without prejudice to dismiss ForeScout from the complaint. Indemnification The Company enters into indemnification provisions in its standard sales contracts with its customers in which it agrees to defend its channel partners and end-customers against third-party claims asserting infringement of certain intellectual property rights, which may include patents, copyrights, trademarks, or trade secrets, and the responsibility to pay judgments entered on such claims. In addition, we indemnify our officers, directors and certain key employees while they are serving in good faith in their respective capacities. To date, there have been no claims under any indemnification provisions.

Debt Agreements

Debt Agreements	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Debt Agreements	Debt Agreements On December 1, 2016, the entire loan balance of $20.1 million provided under a loan and security agreement entered into in October 2012, as amended, and a loan and security agreement entered into in December 2013 were paid in full, and the loan and security agreements entered into in October 2012 and December 2013 were terminated. On December 22, 2016, the Company amended its amended and restated loan and security agreement, which was originally entered into in May 2009 (the “Amended and Restated 2009 Loan and Security Agreement”) to increase the maximum amount of credit available for borrowing under the revolving line of credit to 80% of qualified accounts receivable up to $40.0 million . Additionally, the Company borrowed $30.0 million under the Amended and Restated 2009 Loan and Security Agreement, which carries a maturity date of December 2020 . The combined outstanding balances of the revolving line of credit and the term loan cannot exceed $40.0 million . The agreement is subject to the Company maintaining an adjusted quick ratio of 1.25 . The agreement requires equal monthly installments of principal of $625,000 and monthly interest payments at a fixed interest rate per annum of 3.25% . Concurrent with the final monthly installment payment on the maturity date, the Company is required to pay an additional payment of $825,000 . The amortization expense related to the total discount of the Company’s debt for the years ended December 31, 2015 , 2016 , and 2017 was $0.7 million , $0.7 million , and $0.3 million , respectively. As of December 31, 2016 and 2017 , there was no outstanding balance under the revolving line of credit. The following table presents the carrying value of the Company’s notes payable (in thousands): December 31, 2016 2017 Principal amount of notes payable $ 30,825 $ 23,325 Unamortized debt discount (838 ) (501 ) Net carrying amount of notes payable 29,987 22,824 Less current portion (7,163 ) (7,245 ) Non-current portion of notes payable $ 22,824 $ 15,579 The Amended and Restated 2009 Loan and Security Agreement provides certain financial-related covenants, among others, relating to delivery of audited financial statements to the lenders. The Company was in compliance with respect to all financial-related covenants under its loan agreements as of December 31, 2016 and 2017 .

Redeemable Convertible Preferre

Redeemable Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2017
Temporary Equity Disclosure [Abstract]
Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock Redeemable convertible preferred stock consists of the following as of December 31, 2016 and as of immediately prior to the automatic conversion of redeemable convertible preferred stock into common stock (in thousands, except share amounts): December 31, 2016 Shares Shares Liquidation Original Issuance Carrying Value Series A Preferred 14,742 14,736 $ 1,327 $ 1,327 $ 5,777 Series B Preferred 63,339 63,329 12,288 12,288 32,693 Series C Preferred 47,137 47,132 9,899 9,899 24,539 Series D and D-1 Preferred 7,537,780 7,537,753 16,063 16,063 70,904 Series E Preferred 3,627,391 3,627,381 8,102 8,102 34,306 Series E-1 Preferred 626,195 333,333 2,000 2,000 3,524 Series E-2 Preferred 257,756 257,756 1,933 1,933 5,171 Series F Preferred 3,242,963 3,242,957 30,000 30,000 29,201 Series G Preferred 3,344,544 3,344,540 79,379 79,379 77,739 Total 18,761,847 18,468,917 $ 160,991 $ 160,991 $ 283,854 Upon the closing of the IPO, all shares of the Company's then-outstanding redeemable convertible preferred stock automatically converted into 25,370,616 shares of common stock, including 582,254 additional shares issuable upon conversion of our Series G redeemable convertible preferred stock based on the initial public offering price of $22.00 per share.

Preferred and Common Stock Warr

Preferred and Common Stock Warrants	12 Months Ended
	Dec. 31, 2017
Warrants and Rights Note Disclosure [Abstract]
Preferred and Common Stock Warrants	Preferred and Common Stock Warrants Redeemable Convertible Preferred Stock Warrants The redeemable convertible preferred stock warrants outstanding prior to the IPO were as follows: Issuance Date Exercisable Date Expiration Shares Exercise Price Per Share Series E-1 warrants 10/24/2012 10/24/2012 10/24/2019 292,862 $ 6.00 Concurrent with the closing of the IPO, all shares of outstanding convertible preferred stock warrants were either exercised or converted to common stock warrants. In connection with the conversion of the preferred stock warrants, the Company re-measured the preferred stock warrant liability as of the date of conversion and recorded an increase of $0.3 million to other income (expense), net. The Company also reclassified approximately $4.2 million from preferred stock warrant liability to additional paid-in capital for the estimated fair value of the warrant on the date of conversion. Additionally, the Company recorded $0.1 million to other income (expense), net upon the exercise of preferred stock warrants. All of the above warrants were exercised as of December 31, 2017. In lieu of payment of the aggregate warrant price, the warrant holders elected a "cashless exercise", whereby a portion of the shares equal to the aggregate warrant price were withheld. The average fair market value at the time of exercise was $25.12 , which resulted in 224,691 shares being issued by the Company. Prior to the IPO, the fair values of Series E-1 redeemable convertible preferred stock warrants were estimated using an option pricing method (“OPM”). The OPM uses option theory to value the various classes of a company’s securities in light of their respective claims to the enterprise value. Total stockholders’ equity value is allocated to the various share classes based upon their respective claims on a series of call options with strike prices at various value levels depending upon the rights and preferences of each class. The Black-Scholes closed form option pricing model is employed in this analysis. The inputs to the model include the fair value of Series E-1 redeemable convertible preferred stock, the expected term that the warrants may be outstanding, expected price volatility, risk-free interest rate, and expected dividend yield. The expected term is an estimate of the time to a liquidity event. The expected volatility is based on the historical stock volatilities of the Company’s peer group for a period commensurate with the expected term of the warrant. The risk-free interest rate used is based on the yield available on U.S. Treasury zero-coupon issues with a maturity equivalent with that of the term of the warrants. Generally, increases (decreases) in the fair value of the underlying stock and estimated term would result in a directionally similar impact to the fair value measurement. The following table summarizes the assumptions used to determine the fair value of the Company’s redeemable convertible preferred stock warrants as of December 31, 2016 : December 31, 2016 Fair value of Series E-1 redeemable convertible preferred stock $20.46 Risk-free interest rate 0.7% Expected term 0.8 Expected volatility 61% Dividend yield —% Common Stock Warrants In September 2014, in connection with the issuance of the Series F redeemable convertible preferred stock, the Company issued warrants to the Series F redeemable convertible preferred stockholders to purchase common stock that vest only in the event the Company completes an IPO below a stated per share threshold of $17.00 . Based on the initial public offering price of $22.00 per share, the Common Stock Warrants terminated upon the closing of this offering At December 31, 2016 , common stock warrants to purchase 233,023 shares of our common stock at a weighted-average exercise price of $6.62 per share were outstanding. During the year ended December 31, 2017 , 149,786 common stock warrants were exercised. In lieu of payment of the aggregate warrant price, the warrant holders elected a "cashless exercise", whereby a portion of the shares equal to the aggregate warrant price were withheld. The average fair market value at the time exercise was $25.28 , which resulted in 111,147 shares being issued by the Company. As of December 31, 2017 , 83,237 common stock warrants remained outstanding and exercisable. Common Stock Reserved for Issuance As of December 31, 2017 , common stock reserved, on an as-if converted basis for issuance are as follows: Shares Reserved for future issuance under equity award plans 3,732,143 Common stock options outstanding 9,313,633 Restricted stock units outstanding 4,216,001 Common stock warrants outstanding 83,237 Total common stock reserved for issuance 17,345,014

Common Stock Reserved for Issua

Common Stock Reserved for Issuance	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock Reserved for Issuance	Preferred and Common Stock Warrants Redeemable Convertible Preferred Stock Warrants The redeemable convertible preferred stock warrants outstanding prior to the IPO were as follows: Issuance Date Exercisable Date Expiration Shares Exercise Price Per Share Series E-1 warrants 10/24/2012 10/24/2012 10/24/2019 292,862 $ 6.00 Concurrent with the closing of the IPO, all shares of outstanding convertible preferred stock warrants were either exercised or converted to common stock warrants. In connection with the conversion of the preferred stock warrants, the Company re-measured the preferred stock warrant liability as of the date of conversion and recorded an increase of $0.3 million to other income (expense), net. The Company also reclassified approximately $4.2 million from preferred stock warrant liability to additional paid-in capital for the estimated fair value of the warrant on the date of conversion. Additionally, the Company recorded $0.1 million to other income (expense), net upon the exercise of preferred stock warrants. All of the above warrants were exercised as of December 31, 2017. In lieu of payment of the aggregate warrant price, the warrant holders elected a "cashless exercise", whereby a portion of the shares equal to the aggregate warrant price were withheld. The average fair market value at the time of exercise was $25.12 , which resulted in 224,691 shares being issued by the Company. Prior to the IPO, the fair values of Series E-1 redeemable convertible preferred stock warrants were estimated using an option pricing method (“OPM”). The OPM uses option theory to value the various classes of a company’s securities in light of their respective claims to the enterprise value. Total stockholders’ equity value is allocated to the various share classes based upon their respective claims on a series of call options with strike prices at various value levels depending upon the rights and preferences of each class. The Black-Scholes closed form option pricing model is employed in this analysis. The inputs to the model include the fair value of Series E-1 redeemable convertible preferred stock, the expected term that the warrants may be outstanding, expected price volatility, risk-free interest rate, and expected dividend yield. The expected term is an estimate of the time to a liquidity event. The expected volatility is based on the historical stock volatilities of the Company’s peer group for a period commensurate with the expected term of the warrant. The risk-free interest rate used is based on the yield available on U.S. Treasury zero-coupon issues with a maturity equivalent with that of the term of the warrants. Generally, increases (decreases) in the fair value of the underlying stock and estimated term would result in a directionally similar impact to the fair value measurement. The following table summarizes the assumptions used to determine the fair value of the Company’s redeemable convertible preferred stock warrants as of December 31, 2016 : December 31, 2016 Fair value of Series E-1 redeemable convertible preferred stock $20.46 Risk-free interest rate 0.7% Expected term 0.8 Expected volatility 61% Dividend yield —% Common Stock Warrants In September 2014, in connection with the issuance of the Series F redeemable convertible preferred stock, the Company issued warrants to the Series F redeemable convertible preferred stockholders to purchase common stock that vest only in the event the Company completes an IPO below a stated per share threshold of $17.00 . Based on the initial public offering price of $22.00 per share, the Common Stock Warrants terminated upon the closing of this offering At December 31, 2016 , common stock warrants to purchase 233,023 shares of our common stock at a weighted-average exercise price of $6.62 per share were outstanding. During the year ended December 31, 2017 , 149,786 common stock warrants were exercised. In lieu of payment of the aggregate warrant price, the warrant holders elected a "cashless exercise", whereby a portion of the shares equal to the aggregate warrant price were withheld. The average fair market value at the time exercise was $25.28 , which resulted in 111,147 shares being issued by the Company. As of December 31, 2017 , 83,237 common stock warrants remained outstanding and exercisable. Common Stock Reserved for Issuance As of December 31, 2017 , common stock reserved, on an as-if converted basis for issuance are as follows: Shares Reserved for future issuance under equity award plans 3,732,143 Common stock options outstanding 9,313,633 Restricted stock units outstanding 4,216,001 Common stock warrants outstanding 83,237 Total common stock reserved for issuance 17,345,014

Equity Award Plans

Equity Award Plans	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Award Plans	Equity Award Plans Stock Option and Incentive Plan The 2000 Stock Option and Incentive Plan (the “2000 Plan”) allows for the issuance of stock options and RSUs to employees, non-employees and directors. The Plan provides for incentive stock options to be granted to employees at an exercise price at least equal to 100% of the fair value at the grant date as determined by the Company’s Board of Directors. If a stock-based award is issued to an executive officer that owns more than 10% of the Company’s outstanding common stock, the exercise price will be 110% of the fair market value. The Plan also provides for nonqualified stock options to be issued to employees, non-employees and directors. Options granted generally have a maximum term of 10 years from grant date, allow for early exercise unless otherwise designated by the Board of Directors at the time of grant. Stock options and RSUs generally vest over a four -year period. In October 2017, the Company’s stockholders approved the Company’s 2017 Equity Incentive Plan (the “2017 Plan”). The 2017 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance stock units, performance shares, and performance awards. A total of 3,800,000 shares of the Company’s common stock are reserved for future issuance pursuant to the 2017 Plan. In addition, shares subject to outstanding awards granted under the 2000 Plan, that are canceled, expire, or otherwise terminate without having been exercised in full and shares previously issued under the 2000 Plan that are forfeited to the Company, tendered to or withheld by the Company for the payment of an award’s exercise price or for tax withholding, or repurchased by the Company, may be added to the 2017 Plan (provided that the maximum number of shares that may be added to the Company’s 2017 Plan pursuant to the provision in this sentence is 12,500,000 shares). The number of shares available for future issuance under the Company’s 2017 Plan also includes automatic annual increases on the first day of the Company’s fiscal year beginning with 2018, equal to the lesser of: 3,800,000 shares; 5% of the outstanding shares of common stock as of the last day of the Company’s immediately preceding fiscal year; or such lower number of shares as determined by the administrator of the 2017 Plan. The Company had an early exercise liability of approximately $2.3 million and $1.2 million as at December 31, 2016 , and 2017 , respectively. Including early exercises, the Company has 6,184,187 and 38,266,450 shares of legally outstanding common stock as at December 31, 2016 , and 2017 , respectively. 2017 Employee Stock Purchase Plan In October 2017, the Company’s stockholders approved the 2017 Employee Stock Purchase Plan (the “ESPP”). The ESPP allows eligible employees to purchase shares of the Company’s common stock through payroll deductions and is intended to qualify under Section 423 of the Internal Revenue Code. A total of 800,000 shares of the Company’s common stock are available for sale under the ESPP. The number of shares available for issuance under the Company’s ESPP will also include an automatic, annual increase on the first day of each fiscal year of the Company beginning in 2018, equal to the lesser of: 800,000 shares; 1% of the total number of shares of the Company’s common stock outstanding on the last day of the Company’s immediately preceding fiscal year; or such lower number of shares as determined by the Administrator. The Company’s ESPP provides for consecutive, six -month offering periods. The offering periods are scheduled to start on the first trading day on or after May 20 and November 20 of each year, except for the first offering period which began following the closing of the IPO, and will end on the first trading day on May 18, 2018. Participants may purchase the Company’s common stock through payroll deductions, of up to a maximum of 15% of their eligible compensation. Participation will end automatically upon termination of employment with the Company. The purchase price of the shares will be 85% of the lower of the fair market value of the Company’s common stock on the first trading day of each offering period or on the exercise date. As of December 31, 2017 , no shares of common stock were purchased under the ESPP. The Company selected the Black-Scholes option-pricing model as the method for determining the estimated fair value for the Company’s ESPP. As of December 31, 2017 , total unrecognized compensation cost related to the ESPP was $1.1 million , which will be amortized over a period of 0.4 years. Stock Option Activity The following table summarizes option activity under the Plan and related information (in thousands, except share, per share and contractual life amounts): Options Outstanding Shares Number Weighted- Weighted- Aggregate Balance—December 31, 2015 833,319 8,352,659 $7.72 8.4 $ 93,575 Additional shares authorized 2,030,000 — — Options granted (2,319,385 ) 2,319,385 $17.42 Restricted stock units granted (1,042,000 ) — — Options forfeited 653,434 (653,434 ) $10.10 Options exercised — (431,095 ) $2.53 Balance—December 31, 2016 155,368 9,587,515 $10.13 8.0 $ 61,865 Additional shares authorized 5,926,134 — — Options granted (549,236 ) 549,236 $20.05 Restricted stock units granted (2,354,793 ) — — Restricted stock units forfeited 37,415 — — Options forfeited 517,255 (517,255 ) $14.58 Options exercised — (305,863 ) $5.32 Balance—December 31, 2017 3,732,143 9,313,633 $10.63 7.2 $ 198,012 Options vested and expected to vest—December 31, 2017 9,313,633 $10.63 7.2 $ 198,012 Options vested and exercisable—December 31, 2017 5,675,785 $8.40 6.5 $ 133,316 The weighted-average fair value per share for all options granted was $5.82 , $8.24 , and $9.79 for the years ended December 31, 2015 , 2016 , and 2017 , respectively. The aggregate intrinsic value of employee options exercised was $10.0 million , $6.0 million , and $4.4 million for the years ended December 31, 2015 , 2016 , and 2017 , respectively. The aggregate intrinsic value represents the difference between the Company’s estimated fair value of its common stock and the exercise price of the outstanding options. As of December 31, 2017 , total unrecognized compensation cost related to unvested options was $25.8 million , net of estimated forfeitures, which was expected to be amortized over a weighted-average period of approximately 2.1 years. Restricted Stock Unit (“RSU”) Activity The following table summarizes RSU activity under the Plan and related information (in thousands, except share, per share and contractual life amounts): RSUs Outstanding Number Weighted- Weighted- Aggregate Balance—December 31, 2015 1,069,526 $ 9.06 2.7 $ 20,235 RSUs granted 1,042,000 $ 19.44 RSUs vested (212,903 ) $ 8.39 Balance—December 31, 2016 1,898,623 $ 14.83 1.7 $ 30,720 RSUs granted 2,354,793 $ 25.20 RSUs forfeited (37,415 ) $ 20.44 Balance—December 31, 2017 4,216,001 $ 20.57 1.7 $ 134,448 RSUs vested and expected to vest—December 31, 2017 4,216,001 $ 20.57 1.7 $ 134,448 As of December 31, 2017 , total unrecognized compensation cost related to unvested RSUs was $67.2 million , which was expected to be amortized over a weighted-average period of approximately 2.2 years. Stock-Based Compensation Stock-based compensation expense for both employees and non-employees included in the accompanying consolidated statements of operations is as follows (in thousands): Year Ended December 31, 2015 2016 2017 Cost of revenue: Product $ 16 $ 30 $ 103 Maintenance and professional services 391 1,123 2,291 Research and development 1,101 2,311 6,213 Sales and marketing 2,245 8,084 14,451 General and administrative 4,959 5,286 19,538 Total $ 8,712 $ 16,834 $ 42,596 Certain employees and advisors have been granted stock options with vesting subject to a future liquidity event. Upon the liquidity event, these stock options became fully exercisable, and all of the associated stock-based compensation expense was recognized. The Company granted RSUs to participants that included both a service-based vesting condition and a performance-based vesting condition. The awards generally vest annually over four years, but were subject to a liquidity event prior to any of the shares vesting. Further, in the case of a liquidity event that is an IPO, participants must provide services through 181 days post-IPO before any of the “accrued” time-based shares can vest. Since these options and awards were tied to a liquidity event, and in accordance with the accounting guidance, the liquidity event was not deemed probable until occurrence, the Company did not record any expense for these grants until the completion of the Company’s IPO. Upon the closing of the Company’s IPO on October 31, 2017 , the Company recognized stock-based compensation expense of approximately $21.2 million related to these performance-based stock options and RSUs. During the year ended December 31, 2016 , the Company entered into separation agreements with three employees which resulted in the acceleration of the vesting for stock options. As a result of the modification, the Company recorded stock-based compensation expense of $2.3 million to sales and marketing expense. During the year ended December 31, 2017 , the Company amended its Chief Executive Officer's (“CEO”) employment agreement to provide for accelerated vesting of all of the CEO’s equity awards upon his termination due to death or disability while executing his employment duties. As a result of this modification to the CEO’s vesting terms, the Company expects to record an incremental $7.6 million in stock-based compensation expense over the service period beginning in October 2017 (following the completion of the Company’s IPO), $6.5 million of which was recorded by the Company during the three months ended December 31, 2017 . Determining the Fair Value of Stock Options The fair value of stock option awards granted to employees and to be purchased under ESPP are estimated using the Black-Scholes option-pricing model. The key assumptions within the model are described as follows: Fair Value of Common Stock Prior to the Company’s IPO, the Company’s Board of Directors considered numerous objective and subjective factors to determine the fair value of its common stock. These factors included, but were not limited to (i) contemporaneous third-party valuations of common stock; (ii) the rights and preferences of redeemable convertible preferred stock relative to common stock; (iii) the lack of marketability of common stock; (iv) developments in the business; and (v) the likelihood of achieving a liquidity event, such as an initial public offering or sale of the Company, given prevailing market conditions. Subsequent to its IPO, the Company uses the market closing price for its common stock as reported on the NASDAQ Global Select Market on the date of grant. Risk-Free Interest Rate The risk-free interest rate is based on the rate for a U.S. Treasury zero-coupon issue with a term that approximates the expected life of the option on the date of grant. Expected Term The expected term represents the period that stock-based awards are expected to be outstanding. The expected term is calculated using the simplified method for stock options issued at-the-money. For stock options that have been issued out-of-the-money, the expected term was determined by calculating the midpoint of the simplified method and the contractual life of the option of 10 years , as neither historical experience nor other relevant data was available to estimate the future exercise behavior of out-of-the money stock options. The Company uses the remaining contractual life as the expected term for non-employee awards. Volatility The expected volatility is based on the average historic price volatility for the Company’s publicly traded industry peers based on daily price observations over a period equivalent to the expected term of stock-based awards. The historical volatility data of a peer group is used as there is insufficient trading history for the Company’s common stock. Dividend Yield The Company has never paid dividends and at present, does not expect to pay dividends in the foreseeable future. The assumptions used to determine the grant date fair value of employee stock options and ESPP purchase rights for the periods presented are as follows: Year Ended December 31, 2015 2016 2017 Employee Stock Options Fair value of common stock $8.32 – $18.92 $15.78 – $21.56 $16.73 – $31.16 Risk-free interest rate 0.0% – 2.0% 1.2% – 2.1% 1.9% – 2.2% Expected term (in years) 0.1 – 6.2 6.0 – 8.1 6.0 – 6.1 Volatility 24% – 50% 47% – 51% 46% – 49% Dividend yield —% —% —% Employee Stock Purchase Plan Fair value of common stock $— $— $6.86 Risk-free interest rate —% —% 1.4% Expected term (in years) 0 0 0.52 Volatility —% —% 29.9% Dividend yield —% —% —%

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The components of loss before provision for income taxes are as follows (in thousands): Year Ended December 31, 2016 2017 Domestic $ (76,105 ) $ (92,777 ) Foreign 2,581 3,411 Total $ (73,524 ) $ (89,366 ) The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2016 2017 Current Federal $ 4 $ 17 State 66 50 Foreign 1,273 1,788 Total current 1,343 1,855 Deferred Foreign (95 ) (16 ) Total deferred $ (95 ) $ (16 ) Total $ 1,248 $ 1,839 Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and tax effects of net operating loss and credit carryforwards. Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): December 31, 2016 2017 Deferred tax assets: Federal and state net operating losses $ 50,312 $ 43,410 Research/other credits 862 1,060 Non-deductible and accrued expenses 5,932 4,485 Deferred revenue 12,590 10,438 Stock options 3,400 9,507 Other 1,003 609 Gross deferred tax assets 74,099 69,509 Valuation allowance (73,939 ) (69,320 ) Net deferred tax assets 160 189 Deferred tax liabilities: Property and equipment — (13 ) Net deferred tax liabilities — (13 ) Total $ 160 $ 176 Reconciliation of the statutory federal income tax to the Company’s effective tax (in thousands): Year Ended December 31, 2016 2017 Tax at federal statutory rate $ (24,998 ) $ (30,385 ) State, net of federal benefit 61 60 Stock options 3,225 4,097 Non-deductible warrant expenses (365 ) 272 Tax Reform federal rate change — 36,460 Change in valuation allowance 22,385 (10,512 ) Other 940 1,847 Total $ 1,248 $ 1,839 On December 22, 2017, the President of the United States signed the Tax Cuts and Jobs Act (the “Act”) into law. The legislation significantly changes U.S. tax law by, among other things, lowering corporate income tax rates, implementing a territorial tax system and imposing a mandatory repatriation tax on earnings of foreign subsidiaries. The Tax Reform Act permanently reduces the U.S. corporate income tax rate from a maximum of 35% to a flat 21% rate, effective January 1, 2018. As a result of the change in the U.S. tax rate, the Company’s deferred tax assets and liabilities were remeasured, resulting in a detriment of $36.5 million , which was fully offset by a corresponding change in valuation allowance. The Act provided for a one-time deemed mandatory repatriation of post-1986 undistributed foreign subsidiary earnings and profits ("E&P") through the year ended December 31, 2017 . The Company had a provisional $6.9 million of undistributed foreign E&P subject to repatriation, however, no tax liability was recognized as of the calendar year end because the deemed repatriation is expected to be fully offset by net operating losses. The SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) to address the application of U.S. GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effects of the Tax Reform Act. The Company has recognized the provisional tax impacts related to deemed repatriated earnings for Federal purposes. The Company is in the process of gathering sufficient information to calculate the tax impact for state purposes and has, therefore, not recorded any liability or utilization of state tax attributes. However, the state tax impact of the mandatory repatriation is not expected to be material. The ultimate impact of the mandatory repatriation may differ from the provisional amounts due to additional analysis, changes in interpretations and assumptions the Company has made, or additional regulatory guidance that may be issued. The accounting is expected to be complete when the 2017 U.S. corporate income tax return is filed in 2018. The Company is still in the process of analyzing other provisions (Global Intangible Low-Taxed Income (“GILTI”), base erosion anti-abuse tax (“BEAT”), etc.) of this legislation which may impact the Company’s effective tax rate in future years. For the years ended December 31, 2016 and 2017 , the Company recorded a tax provision of $1.3 million and $1.8 million , respectively, representing effective tax rate of (1.7)% and (2.1)% for the years ended December 31, 2016 and 2017 , respectively. The key components of the income tax provision primarily consist of foreign income taxes, income tax reserves, and U.S. state minimum taxes. The difference in the effective tax rate for the years ended December 31, 2016 and 2017 is primarily due to change in the uncertain tax positions as a result of a statutory income tax and withholding tax audit. A valuation allowance has been provided to reduce the deferred tax asset to an amount management believes is more likely than not to be realized. The valuation allowance increased by $25.0 million and decreased by $4.6 million for the years ended December 31, 2016 and 2017 , respectively. As of December 31, 2017 , the Company had net operating loss carryforwards for federal income tax purposes of approximately $180.1 million , which begin to expire in 2021 if not utilized. The Company also has California net operating loss carryforwards of approximately $22.0 million , which begin to expire in 2028 if not utilized. The Company also has other state net operating loss carryforwards of approximately $76.6 million , which begin to expire in 2018 if not utilized. The Company has federal and California research and development credit carryforwards of $0.7 million and $0.5 million , respectively. The federal research and development credits will begin to expire in 2035 , if not utilized. California research and development credits can be carried forward indefinitely. The Company has an immaterial amount of foreign tax credits. Utilization of the Company’s net operating loss carryforwards may be subject to substantial annual limitation due to the ownership change limitations provided by the Internal Revenue Code and similar state provisions. Such a limitation could result in the expiration of the net operating loss carryforwards before utilization. The Company performed an ownership change analysis from inception to the balance sheet date of December 31, 2017 and $2.8 million of net operating loss carryforwards were written off due to the limitation. The Company provides U.S. income taxes on the earnings of foreign subsidiaries, unless the subsidiaries’ earnings are considered indefinitely reinvested outside the United States. As of December 31, 2017 , U.S. income taxes have been provided for on the cumulative total of $6.9 million of undistributed earnings from its foreign subsidiaries. Any earnings if distributed by the foreign subsidiary would not result in any liability since they would be offset by net operating losses. Uncertain Tax Positions For benefits to be realized, a tax position must be more likely than not to be sustained upon examination. The amount recognized is measured as the largest amount of benefit that is greater than 50 percent likely of being realized upon settlement. As a result of the implementation of these provisions, the Company did not recognize any adjustments to retained earnings for uncertain tax positions. A reconciliation of the gross unrecognized tax benefit is as follows (in thousands): Year Ended December 31, 2016 2017 Unrecognized tax benefits at the beginning of the period $ 254 $ 1,050 Additions for tax positions taken in prior years 185 248 Additions for tax positions taken in current year 611 845 Settlements with taxing authorities — (416 ) Unrecognized tax benefits at the end of the period $ 1,050 $ 1,727 It is the Company’s policy to recognize interest and penalties related to income tax matters in income tax expense. During the years ended December 31, 2016 , and 2017 , the Company did not recognize any significant accrued interest and penalties related to uncertain tax positions. As of December 31, 2016, the Company had $0.4 million of uncertain tax positions relating to a statutory income tax audit which was settled and paid during the six months ended June 30, 2017. The Company does not expect any settlements in the next 12 months. The Company is subject to federal income tax as well as income tax in multiple state and foreign jurisdictions. Due to the Company’s net operating loss carryforwards, all tax years since inception remain subject to examination for United States federal tax returns, and fiscal year 2016 remains subject to examination for Israel. There are tax years which remain subject to examination in various other jurisdictions that are not material to the Company’s financial statements.

Net Loss Per Share

Net Loss Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss Per Share	Net Loss per Share Net loss per share of common stock is computed using the two-class method required for participating securities based on their participation rights. All series of redeemable convertible preferred stock are participating securities as the holders are entitled to participate in common stock dividends with common stock on an as converted basis. Basic net loss per share is computed by dividing net loss attributable to common stockholders by basic weighted-average shares outstanding during the period. All participating securities are excluded from basic weighted-average shares outstanding. In computing diluted net loss attributable to common stockholders, undistributed earnings are re-allocated to reflect the potential impact of dilutive securities. Diluted net loss per share attributable to common stockholders is computed by dividing net loss attributable to common stockholders by diluted weighted-average shares outstanding, including potentially dilutive securities, unless anti-dilutive. The following table presents the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts): Year Ended December 31, 2015 2016 2017 Net loss $ (27,260 ) $ (74,774 ) $ (91,205 ) Deemed dividend on the conversion of Series G redeemable convertible preferred stock — — 12,810 Net loss attributable to common stockholders $ (27,260 ) $ (74,774 ) $ (104,015 ) Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted 4,121,852 5,609,187 11,405,356 Net loss per share attributable to common stockholders, basic and diluted $ (6.61 ) $ (13.33 ) $ (9.12 ) The following securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because their inclusion would reduce the net loss per share. Year Ended December 31, 2015 2016 2017 Options to purchase common stock 8,351,589 9,587,572 9,313,633 Unvested early exercised common shares 474,148 329,957 146,468 Unvested restricted stock units 1,069,524 1,898,621 4,216,001 Shares estimated under ESPP — — 220,721 Warrants to purchase common stock 233,023 233,023 83,237 Redeemable convertible preferred stock 24,620,991 24,788,362 — Warrants to purchase redeemable convertible preferred stock 292,862 292,862 —

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Employee Benefit Plans	Employee Benefit Plans Israeli labor laws and agreements require the Company’s Israeli subsidiary to make severance payments to retired or dismissed Israeli employees, as well as to employees leaving employment under certain other circumstances. The Company’s severance obligations to employees are measured based upon length of service and latest monthly salary amount. The Company has recorded a non-current liability of $2.0 million and $2.6 million as of December 31, 2016 and 2017 , respectively, for the estimated amount of accrued severance benefits. The deposits are held with a severance pay fund in order to fund the obligation, which totaled $1.7 million and $2.1 million as of December 31, 2016 and 2017 , respectively, and are recorded as a non-current asset in the accompanying consolidated balance sheets. A 401(k) tax-deferred savings plan (the “401(k) Plan”) was established that covers substantially all of the Company’s U.S. employees. The 401(k) plan permits participants to make contributions by salary deduction pursuant to Section 401(k) of the Internal Revenue Code. The Company is responsible for administrative costs of the 401(k) Plan. The Company provided for a match of 50% of the first 6% of an eligible employee’s compensation contributed, up to a maximum matching dollar amount of $2,000 for a year. Matching contributions under the 401(k) Plan are 100% vested when made. Pre-tax 401(k) and post-tax Roth 401(k) contributions are allocated to each participant’s individual account and are then invested in selected investment alternatives according to the participants’ directions. The 401(k) Plan is intended to qualify under Sections 401(a) and 501(a) of the Code. As a tax-qualified retirement plan, pre-tax contributions are not taxable to the employees until distributed from the 401(k) Plan, and post-tax contributions are not exempt from taxes at the time of contribution but the earnings accumulated are tax-free and are not taxable upon distribution. All contributions are deductible by the Company when made. The Company’s contributions to the 401(k) Plan were $0.5 million , $1.0 million , and $1.1 million for the years ended December 31, 2015 , 2016 , and 2017 , respectively.

Segment Information

Segment Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Information	Segment Information The Company’s business is conducted globally. The Company’s chief operating decision maker is the Chief Executive Officer who reviews financial information presented on a consolidated basis accompanied by information about revenue by geographic region for purposes of allocating resources and evaluating financial performance. There is one business activity and there are no segment managers who are held accountable for operations, operating results, and plans for levels, components, or types of products or services below the consolidated unit level. Accordingly, there is a single reporting segment and operating unit structure. Revenue by geographic area is attributed based on the billing address of the customer and is as follows (in thousands): Year Ended December 31, 2015 2016 2017 Revenue: Americas United States $ 99,519 $ 133,615 $ 162,479 Other Americas 3,865 4,949 6,176 Total Americas 103,384 138,564 168,655 Europe, Middle East, and Africa (“EMEA”) 15,023 18,918 36,300 Asia Pacific and Japan (“APJ”) 7,552 9,359 15,916 Total revenue $ 125,959 $ 166,841 $ 220,871 Long-lived assets, net by geographic area are attributed based on legal entity structure and are as follows (in thousands): December 31, 2016 2017 Long-lived assets, net: United States $ 21,141 $ 18,989 Israel 3,051 3,453 Other 344 818 Total long-lived assets, net $ 24,536 $ 23,260

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions One member of the Company’s board of directors previously served as an executive of a company that is also one of the Company’s customers and vendors (“Company A”). Another member of the Company’s board of directors is currently serving as Chairman of the Board of Directors of Company A. The Company maintains several on-going commercial relationships with Company A. For the years ended December 31, 2015 , 2016 , and 2017 as part of the on-going commercial relationships with this company, the Company made payments of approximately $77,000 , $591,000 , and $157,000 , respectively, to this company. For the years ended December 31, 2015 , 2016 , and 2017 , the Company sold products, maintenance, and professional services and received payments from this company of approximately $496,000 , $294,000 , and $1,000 , respectively. Also, one member of the Company’s board of directors is currently serving on the board of directors of another of the Company’s vendors (“Company B”). The Company maintains an on-going commercial relationship with this Company B. For the years ended December 31, 2016, and 2017 as part of the on-going commercial relationships with Company B, the Company made payments of approximately $0.2 million , and $0.3 million , respectively to Company B. The Company did not make any payments to Company B for the year ended December 31, 2015 .

Description of Business and S23

Description of Business and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	The consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The Company’s consolidated financial statements include the results of ForeScout Technologies, Inc. and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	The preparation of financial statements in conformity with GAAP requires management to make use of estimates and assumptions that affect the reported amounts in the consolidated financial statements and accompanying notes. These estimates form the basis of judgments made about carrying values of assets and liabilities, which are not readily apparent from other sources. The areas where management has made estimates requiring judgment include, but are not limited to, the allocation of revenue in multiple element arrangements, sales return reserve, accruals, stock-based compensation including the fair value of common stock, redeemable convertible preferred stock warrant liabilities, and provision for income taxes, including related reserves. Actual results could differ materially from those estimates.
Segment information	The chief operating decision maker (“CODM”) is the Chief Executive Officer who reviews financial information presented on a consolidated basis. The Company has one business activity and there are no segment managers who are held accountable by the CODM for operations, operating results and planning for levels or components below the consolidated level. The Company operates in one segment.
Concentrations	Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash, cash equivalents, marketable securities, accounts receivable, severance pay deposits, and restricted cash. The Company maintains all of its cash and cash equivalents in interest-bearing bank accounts and money market accounts. Management believes that the financial institutions that hold the Company’s cash and cash equivalents are financially sound and exposed to minimal credit risk. Deposits held with banks generally exceed the amount of insurance provided on such deposits. Accounts receivable are primarily derived from the Company’s customers, including distributors and resellers representing various geographical locations. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable, and, if necessary, an allowance for doubtful accounts is maintained for estimated potential credit losses.
Foreign Currency	The functional currency of the Company’s foreign subsidiaries is the U.S. dollar. Monetary assets and liabilities are remeasured using the current exchange rate at the balance sheet date. Non-monetary assets and liabilities and capital accounts are remeasured using historical exchange rates. Revenue and expenses have been remeasured using the average exchange rates in effect during each period. Foreign currency remeasurement gains and losses are recorded in other expense, net.
Cash and Cash Equivalents	The Company considers all highly liquid investments held at financial institutions with original maturities of three months or less at date of purchase to be cash equivalents. Cash and cash equivalents are stated at cost, which approximates fair value.
Marketable Securities	The Company’s marketable securities consist primarily of commercial paper, corporate debt securities, and U.S. government agency securities. The Company’s marketable securities are classified as available-for-sale and are reported at fair value. The Company determines any realized gains or losses on the sale of available-for-sale securities on a specific identification method, and such gains and losses are recorded as a component of other income (expense), net on our consolidated statements of operations. Unrealized gains and losses of the available-for-sale securities are excluded from earnings and reported as a component of accumulated other comprehensive income (loss). The Company has classified and accounted for its marketable securities as available-for-sale. After consideration of the Company’s risk versus reward objectives, as well as the Company’s liquidity requirements, the Company may sell these securities prior to their stated maturities. As the Company views these securities as available to support current operations, the Company classifies highly liquid securities with maturities beyond 12 months as current assets under the caption marketable securities in the Consolidated Balance Sheets. Marketable securities are considered impaired when a decline in fair value is judged to be other-than-temporary. The Company considers available quantitative and qualitative evidence in evaluating potential impairment of the marketable securities on a quarterly basis. If the cost of an individual investment exceeds its fair value, the Company evaluates, among other factors, general market conditions, the duration and extent to which the fair value is less than cost, and the Company’s intent and ability to hold the investment. Once a decline in fair value is determined to be other-than-temporary, the Company will record an impairment charge and establish a new cost basis in the investment.
Accounts Receivable	Trade accounts receivable are recorded at the invoiced amount, net of allowances for doubtful accounts. The Company assesses its trade accounts receivable for doubtful accounts based on the collectability of accounts. Management regularly reviews the adequacy of the allowance for doubtful accounts by considering the age of each outstanding invoice, each customer’s expected ability to pay, and the collection history with each customer, to determine whether a specific allowance is appropriate. Accounts receivable that are deemed uncollectible are charged against the allowance for doubtful accounts.
Inventory	Inventory primarily consists of finished goods hardware appliances and is stated at the lower of cost or market determined using the specific identification method. Inventory that is obsolete or in excess of forecasted demand is written down to its estimated realizable value. Inventory write-downs, once established, are not reversed as they establish a new cost basis for the inventory.
Property and Equipment	Property and equipment is stated at cost. Depreciation is computed using the straight-line method over the estimated useful lives of the assets, generally three to five years. Demonstration units are not resold after use and are depreciated over the estimated useful life of three years or less. Leasehold improvements are depreciated over the shorter of the estimated useful lives of the improvements or the remaining lease term.
Impairment of Long-Lived Assets	Management reviews long-lived assets for events and changes in circumstances that may indicate that carrying amounts of long-lived assets, including property and equipment, may not be recoverable. When such events or circumstances occur, recoverability of these assets is measured by a comparison of the carrying value to the future undiscounted cash flows the assets are expected to generate. If long-lived assets are considered to be impaired, the impairment to be recognized would equal the amount by which the carrying value of the asset exceeds its fair market value. To date, the Company has not recorded any significant impairment to its long-lived assets.
Deferred Offering Costs	Deferred offering costs consisted of fees and expenses incurred in connection with the sale of the Company’s common stock in its IPO, including direct incremental legal, consulting, accounting fees, and other IPO-related costs. Upon completion of the Company’s IPO, these deferred offering costs were reclassified to stockholders’ deficit and offset against the proceeds of the offering.
Product Warranty	The Company provides a standard 90 day warranty on its hardware and software products. The Company also offers its customers post-contract support (“PCS”), which includes a warranty of between one to five -years on hardware. The Company will also provide its customers software releases or updates during the PCS term. The Company accrues for estimated standard warranty costs for those customers that do not purchase PCS at the time of product shipment. These potential warranty claims are accrued as a component of product cost of revenue based on historical experience and other data, which is reviewed periodically for adequacy. Warranty costs associated with PCS are expensed as incurred. To date, the Company has not incurred nor accrued any significant costs associated with product warranty.
Contract Manufacturer Liabilities	Manufacturing, repair, and supply chain management operations are outsourced to a third party contract manufacturer. These costs are a significant portion of product cost of revenue. Although the Company is contractually obligated to purchase manufactured products, the Company generally does not own the manufactured products as product title transfers from the contract manufacturer to the Company and immediately to the customer upon shipment. The contract manufacturer assembles the Company’s products using design specifications, quality assurance programs, and standards that the Company establishes. Components are procured and assembled based on the Company’s demand forecasts. These forecasts represent management’s best estimates of future demand for the products based upon historical trends and analysis from sales and operations functions as adjusted for overall market conditions. The Company accrues for costs for contractual manufacturing commitments in excess of its forecasted demand, including costs incurred for excess components or for the carrying costs incurred by the contract manufacturer. To date, the Company has not accrued any significant contract manufacturer liabilities.
Redeemable Convertible Preferred and Common Stock Warrant Liabilities	Upon completion of the Company's IPO in October 2017, there were no freestanding warrants to purchase shares of convertible preferred stock. As such, no preferred stock warrant liability remained outstanding after the IPO. Before the Company's IPO, freestanding warrants related to shares that are redeemable or contingently redeemable were classified as a liability in the Company’s consolidated balance sheet. The convertible preferred stock warrants were subject to re-measurement at each balance sheet date, and any change in fair value was recognized in the consolidated statements of operations. The Company adjusted the redeemable convertible preferred stock warrant liability to the estimated fair value of the warrants until either the exercise or the completion of the Company’s IPO, at which time the redeemable convertible preferred stock issuable upon exercise of the warrants became warrants to purchase common stock and the related liability was reclassified to additional paid-in capital in stockholders' equity (deficit).
Severance Pay Deposits and Accrued Severance Pay Liability	The Company records a severance pay asset and liability on its consolidated balance sheets related to its employees located in Israel. Under Israeli law and labor agreements, the Company is required to make severance and pension payments to retired or dismissed employees and to employees leaving employment in certain other circumstances. Liabilities for severance pay are calculated pursuant to Israeli severance pay law using the most recent monthly salary for the employees, multiplied by the number of years of employment, and are included in accrued severance pay liability in the Company’s balance sheets. The Company’s liability at each respective balance sheet date for its Israeli employees is fully accrued in the accompanying consolidated financial statements. The severance liability is funded through monthly deposits to the employee’s pension and management insurance carriers. The fair value of this deposit is recorded in severance pay deposits in the Company’s consolidated balance sheets.
Revenue Recognition	The Company derives its revenue from sales of products and associated maintenance and professional services. The Company’s CounterACT and Enterprise Manager products are sold as hardware appliances embedded with the Company’s software, or Physical Appliances, or as software only, or Virtual Appliances. The Company also recently started offering, in limited quantities to a small number of large enterprises, CounterACT and Enterprise Manager together as a software only license (“Enterprise License Software”). The Company’s Enterprise License Software is either sold with separate hardware or without hardware, depending on the end-customer’s selection. The Company’s portfolio of Extended Modules are sold as software add-ons to CounterACT and Enterprise Manager. The Company accounts for the sale of Physical Appliances, and Enterprise License Software sold with separate hardware (“Hardware Products”) pursuant to Financial Accounting Standards Board, or FASB, Accounting Standard Codification Topic (“ASC”) 605-25, Revenue Recognition: Multiple Element Arrangements. The Company accounts for the sale of Virtual Appliances, Enterprise License Software sold without hardware, and Extended Modules as software deliverables (“Software Products”) pursuant to FASB, ASC Topic 985-605, Software Revenue Recognition. All of the Company’s products are sold with a perpetual license. The Company recognizes revenue when all of the following criteria are met: • Persuasive Evidence of an Arrangement Exists. The Company relies upon binding sales agreements and/or purchase orders to provide evidence of an arrangement. • Delivery has Occurred. The Company uses shipping documents and/or electronic transmissions to evidence delivery of products. • The Fee is Fixed or Determinable. The Company determines whether the fee is fixed or determinable based on the payment terms associated with the transaction. • Collectability is Reasonably Assured. The Company evaluates collectability based on credit analysis and payment history. Payments from the Company’s distributors and resellers are not contingent on the distributors’ and resellers’ success in sales to end-customers. The Company’s distributors and resellers do not stock hardware appliances and have no stock rotation rights. Most of the Company’s sales, other than renewals of support and maintenance, are multiple element arrangements with a combination of Physical Appliances, Virtual Appliances, Extended Modules, Enterprise License Software and hardware sold separately, support and maintenance and professional services. For multiple element arrangements, the arrangement consideration is allocated to software deliverables as a group and non-software deliverables as a second group based on a relative selling price hierarchy. The relative selling price hierarchy is based on: (i) vendor-specific objective evidence of fair value (“VSOE”) if available, (ii) third-party evidence of selling price (“TPE”) if VSOE is not available, or (iii) best estimate of the selling price (“BESP”) if neither VSOE nor TPE is available. Hardware Product revenue is recognized at the time of delivery, provided that all other revenue recognition criteria have been met. Software Product revenue is recognized at the time of delivery if VSOE is established for all undelivered related items. If VSOE does not exist for one or more undelivered items, revenue from the software portion of the arrangement is deferred until the delivery of all items has begun and is then recognized ratably over the remaining related support and maintenance service period. Support and maintenance revenue is generally recognized ratably over the contractual service period, which is typically one to three years , but can be up to five years . Professional services revenue is generally recognized as the services are rendered. For Hardware Products, the Company determined that VSOE and TPE cannot be established. As a result, the Company uses BESP to determine the relative selling price at which a transaction would take place if the hardware product was sold on a stand-alone basis. For Hardware Product related maintenance and professional services, the Company uses either VSOE or BESP when VSOE and TPE cannot be established. In determining the BESP for a product or service, the Company considers historical data including, but not limited to, product family, pricing practices, standalone sales, the nature and size of the customer, contractually stated prices, and geographical region. The Company limits the amount of revenue recognized for delivered elements to an amount that is not contingent upon future delivery of additional products or services or meeting of any specified performance conditions. In multiple-element arrangements that include software, revenue is allocated to each separate unit of accounting for the non-software deliverables, as well as the software deliverables as a group, using the relative estimated selling prices of each of the deliverables in the arrangement based on the aforementioned selling price hierarchy. The arrangement consideration allocated to the software deliverables as a group is then allocated to each software deliverable separately using the residual method based on the fair value of each of the undelivered deliverables, using VSOE. The Company typically determines VSOE based on its normal pricing and discounting practices for the specific service when sold separately. The Company establishes VSOE on software related support and maintenance using the bell-shaped curve approach. Under this approach, the Company concludes that VSOE exists if a substantial majority of recent stand-alone renewal transactions are priced within a narrow range. For Enterprise License Software, the Company established VSOE on support and maintenance prior to the occurrence of actual renewals, based on management’s ability to establish support and maintenance renewal rates. The Company ensures that such established VSOE is supported by contractually stated renewal rates. Beginning on January 1, 2016, the Company has established VSOE for professional services, and support and maintenance on Software Products, except Extended Modules. Revenue is reported net of sales taxes. Sales commissions and other incremental costs to acquire contracts are expensed to sales and marketing expense as incurred.
Deferred Revenue and Deferred Cost of Revenue	After receipt of a customer order, any amounts billed in excess of revenue recognized are recorded as deferred revenue. Deferred revenue consists of amounts that have been invoiced but that have not been recognized as revenue. Deferred revenue that is expected to be recognized within the succeeding 12 month period is recorded as current deferred revenue and the remaining amount is recorded as non-current deferred revenue. Deferred cost of revenue includes direct and incremental costs related to product sales provided for contracts under which revenue has been deferred as the earnings process has not been completed. Deferred cost of revenue that is expected to be realized within the succeeding 12 month period is recorded as current deferred cost of revenue and the remaining amount is recorded as non-current other assets.
Customer Deposits	Customer deposits represents amounts received from customers in advance for future orders of goods or services.
Software Development Costs	Software development costs are not capitalized as the software development process is essentially completed concurrent with the establishment of technological feasibility. As such, all software development costs are expensed as incurred and included in research and development expense in the accompanying consolidated statements of operations.
Advertising Costs	Advertising costs include costs incurred on print, broadcast, and online advertising. Advertising costs are expensed as incurred and included in sales and marketing expense in the accompanying consolidated statements of operations.
Stock-Based Compensation	Stock-based compensation for employees is measured based on the grant date fair value of the award and is expensed over the requisite service period, which is generally the vesting period. The Company accounts for stock-based compensation to non-employees using the fair value approach. Equity awards to non-employees are subject to remeasurement at each reporting period over their vesting terms. The fair value of option awards is determined on the date of grant using the Black-Scholes option pricing model. In applying the Black-Scholes option pricing model, the Company’s determination of the fair value of the option award on the grant date is affected by the Company’s estimated fair value of the underlying common stock, as well as assumptions relating to subjective variables. These variables include the expected term of the award, the expected volatility of the common stock price, the risk-free interest rate, and the expected dividend yield of common stock. The fair value of restricted stock units (“RSUs”) is determined on the date of grant using the Company’s estimated fair value of the underlying common stock. Prior to January 1, 2017, for awards with a service condition only, the Company recognized stock-based compensation expense over the service period on a straight-line basis, net of forfeitures. For awards with both a service and performance condition, stock-based compensation expense is recognized over the service period using an accelerated attribution method once the performance conditions become probable. Beginning January 1, 2017 with the adoption of ASU 2016-09, the Company elected to recognize forfeitures as they occur, and no longer estimates a forfeiture rate when calculating the stock-based compensation for equity awards. Stock-based compensation for the years ended December 31, 2015 and 2016 was calculated using an estimated forfeiture rate based on an analysis of the Company’s actual historical forfeitures.
Income Taxes	Deferred income taxes are recognized using the asset and liability method, whereby deferred tax assets and liabilities are recognized for the expected future tax consequences attributable to differences between the Company’s (1) financial statement carrying amounts and their respective tax bases and (2) operating loss and tax credit carryforwards. Valuation allowances are provided when the expected realization of tax assets does not meet a more-likely-than-not criterion. Due to the Company’s lack of earnings history, the U.S. net deferred tax assets have been fully offset by a valuation allowance. The Company recognizes tax benefits from uncertain tax positions if it is more likely than not that the tax position will be sustained upon examination by a taxing authority based on the technical merits of the position. The tax benefits recognized from such positions are measured based on the largest benefit that has a greater than 50% likelihood to be realized upon settlement. The Company recognizes accrued interest and penalties related to unrecognized tax benefits in income tax expense in the accompanying consolidated statements of operations, when and if incurred. On December 22, 2017, the President of the United States signed the Tax Cuts and Jobs Act (the “Act”) into law. The legislation significantly changes U.S. tax law by, among other things, lowering corporate income tax rates, implementing a territorial tax system and imposing a mandatory repatriation tax on earnings of foreign subsidiaries. The Tax Reform Act permanently reduces the U.S. corporate income tax rate from a maximum of 35% to a flat 21% rate, effective January 1, 2018.
Recent Accounting Pronouncements	In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-09 (Topic 606), Revenue from Contracts with Customers (“ASU 2014-09”), related to revenue from contracts with customers, which, along with amendments issued in 2015 and 2016, will supersede nearly all current GAAP guidance on this topic and eliminate industry-specific guidance. Under the new standard, revenue is recognized when a customer obtains control of promised goods or services and is recognized in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. In addition, the standard requires disclosure of the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The guidance permits two methods of adoption: retrospectively to each prior reporting period presented (“full retrospective method,”) or retrospectively with the cumulative effect of applying the guidance recognized in retained earnings as of the date of adoption (“modified retrospective method”). The Company will adopt the new standard using the full retrospective method effective January 1, 2018. To date, the Company has evaluated the impacts of adoption of the new standard on its accounting policies, processes, and system requirements and has assigned internal resources, in addition to the engagement of third party service providers, to assist in the evaluation. The most significant impact relates to the accounting for Software Products as VSOE for support and maintenance on Software Products prior to January 1, 2016 was not established, and recorded all Software Product related revenue ratably over the contractually committed support and maintenance period. Under the new standard the requirement to have VSOE for undelivered elements is eliminated and an entity may be required to recognize Software Product revenue at the time of delivery, and any related professional services revenue as services are provided to the customers. The Company expects revenue allocated from future deliverables (primarily support and maintenance) to Physical Appliances to be recognized upon delivery under the new guidance when the standalone selling price is different from the contract price. Currently, such differences are recognized over the contractual support and maintenance period. Additionally, the new standard requires the capitalization of costs to obtain a contract, primarily sales commissions, and amortization of these costs over the contract period or estimated customer life which will result in the recognition of a deferred charge on our balance sheets. The Company currently expenses all sales commissions and other incremental costs to acquire contracts as incurred. The Company estimates the impacts to the following account balances after the adoption of Topic 606. Adoption of the standard will result in: • A net increase in revenue for the years ended December 31, 2016 and 2017, respectively, due to the changes in accounting for Software Products revenue recognition and for revenue allocated from future deliverables to Physical Appliances; • A decrease in sales and marketing expense for the years ended December 31, 2016 and 2017, respectively, due to a change in the accounting for commissions; • A decrease in loss from operations for the years ended December 31, 2016 and 2017, respectively, due to the changes above related to sales and marketing expense and revenue; • An increase of deferred commissions as of December 31, 2016 and 2017, respectively, driven by the change in the accounting for commissions; • A reduction of deferred revenue as of December 31, 2016 and 2017, respectively, driven primarily by the upfront recognition of Software Products revenue. In July 2015, the FASB issued ASU No. 2015-11 (Topic 330), Simplifying the Measurement of Inventory . The guidance simplifies the measurement of inventory by requiring inventory to be measured at the lower of cost and net realizable value. The standard is effective for annual and interim periods within those fiscal years, beginning after December 15, 2016, and should be applied prospectively. The Company adopted this standard in the first quarter of 2017. The adoption of this standard did not have a material impact on the Company’s consolidated financial statements. In February 2016, the FASB issued ASU No. 2016-02 (Topic 842), Leases . The new guidance requires lessees to recognize right-of-use assets and lease liabilities for those leases classified as operating leases under previous U.S. GAAP. The standard is effective for annual and interim periods within those fiscal years, beginning after December 15, 2018, and will be applied on a modified retrospective basis, with the option to elect certain practical expedients. Early adoption is permitted. The Company plans to adopt this standard on January 1, 2019. The Company is currently evaluating the impact of the adoption of this standard on its consolidated financial statements. In March 2016, the FASB issued ASU No. 2016-09 (Topic 718), Improvements to Employee Share-Based Payment Accounting (“ASU 2016-09”). This standard is intended to simplify several areas of accounting for stock-based compensation arrangements, including the income tax impact, classification on the statement of cash flows and forfeitures. ASU 2016-09 is effective for annual and interim periods within those fiscal years, beginning after December 15, 2016. The Company adopted this standard in the first quarter of 2017 and elected to account for forfeitures as they occur, rather than estimate expected forfeitures. The change has been applied on a modified retrospective basis that resulted in a $34,000 cumulative-effect adjustment to accumulated deficit as of January 1, 2017, the date of adoption. The adoption of this guidance also requires that excess tax benefits and tax deficiencies be recorded in the statement of operations as opposed to additional paid-in capital when the awards vest or are settled, and has been applied on a prospective basis. As a result, deferred tax assets increased by $2.3 million as of January 1, 2017, offset by valuation allowance, due to tax deductions related to equity compensation greater than compensation recognized for financial reporting. In November 2016, the FASB issued ASU No. 2016-18 (Topic 230), Statement of Cash Flows: Restricted Cash . The new standard requires an entity to show the changes in the total of cash, cash equivalents, restricted cash and restricted cash equivalents in the statement of cash flows, and an entity will no longer present transfers between cash and cash equivalents and restricted cash and restricted cash equivalents in the statement of cash flows. The standard is effective for annual and interim periods within those fiscal years, beginning after December 15, 2017, and should be applied retrospectively. The Company will adopt this standard on January 1, 2018.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Assets and Liabilities	The following table presents the fair value of the Company’s financial assets and liabilities according to the fair value hierarchy (in thousands): December 31, 2016 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Financial Assets Cash and cash equivalents: Cash $ 42,499 $ — $ — $ 24,526 $ — $ — Money market accounts 37,166 — — 38,483 — — Total cash and cash equivalents 79,665 — — 63,009 — — Marketable securities: Commercial paper — — — — 40,610 — Corporate debt securities — — — — 58,948 — U.S. government securities — — — — 23,826 — Total marketable securities — — — — 123,384 — Restricted cash 4,212 — — 4,348 — — Total financial assets $ 83,877 $ — $ — $ 67,357 $ 123,384 $ — Financial Liabilities Warrant liabilities $ — $ — $ 4,874 $ — $ — $ —
Schedule of Activity for Warrant Liabilities	The following table presents the summary of the changes in the fair value of the Company’s Level 3 financial instruments as follows (in thousands): Level 3 Balance as of December 31, 2015 $ 5,978 Revaluation of warrant liabilities (1,104 ) Balance as of December 31, 2016 4,874 Revaluation of warrant liabilities 727 Reclassification of preferred stock warrants to common stock warrants upon IPO (4,173 ) Exercise of preferred stock warrants (1,428 ) Balance as of December 31, 2017 $ —

Marketable Securities (Tables)

Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Schedule of Unrealized Losses and Fair Value of Available-for-Sale Securities	The following table summarizes the unrealized losses and fair value of the Company’s marketable securities as of December 31, 2017 (in thousands): December 31, 2017 Amortized Cost Unrealized Losses Fair Value Marketable securities: Available-for-sale: Commercial paper $ 40,610 $ — $ 40,610 Corporate debt securities 59,031 (83 ) 58,948 U.S. government securities 23,855 (29 ) 23,826 Total marketable securities $ 123,496 $ (112 ) $ 123,384
Investments Classified by Contractual Maturity Date	The following table summarizes the amortized cost and fair value of the Company’s available-for-sale securities as of December 31, 2017 , by the contractual maturity date (in thousands): December 31, 2017 Amortized Cost Fair Value Due within one year $ 83,419 $ 83,374 Due between one and five years 40,077 40,010 Total $ 123,496 $ 123,384
Schedule of Unrealized Loss on Marketable Securities	For individual marketable securities that have been in a continuous unrealized loss position, the fair value and gross unrealized loss for these securities aggregated by investment category and length of time in an unrealized position are presented in the following tables (in thousands): December 31, 2017 Less Than 12 Months Greater Than 12 Months Total Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss Corporate debt securities $ 58,581 $ (83 ) $ — $ — $ 58,581 $ (83 ) U.S. government securities 23,771 (29 ) — — 23,771 (29 ) Total $ 82,352 $ (112 ) $ — $ — $ 82,352 $ (112 )

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Schedule of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): December 31, 2016 2017 Leasehold improvements $ 18,158 $ 18,617 Computer, equipment and software 7,246 9,835 Furniture and fixtures 3,609 3,577 Demonstration units 1,824 2,528 Construction in progress 111 14 Total property and equipment 30,948 34,571 Less: accumulated depreciation (6,412 ) (11,311 ) Total property and equipment, net $ 24,536 $ 23,260

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments	As of December 31, 2017 , the future minimum lease payments by fiscal year under non-cancelable leases are as follows (in thousands): Years Ending December 31, Operating 2018 $ 6,100 2019 4,882 2020 3,255 2021 3,356 2022 3,460 2023 and thereafter 14,254 Total $ 35,307

Debt Agreements (Tables)

Debt Agreements (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Carrying Value of Notes Payable	The following table presents the carrying value of the Company’s notes payable (in thousands): December 31, 2016 2017 Principal amount of notes payable $ 30,825 $ 23,325 Unamortized debt discount (838 ) (501 ) Net carrying amount of notes payable 29,987 22,824 Less current portion (7,163 ) (7,245 ) Non-current portion of notes payable $ 22,824 $ 15,579

Redeemable Convertible Prefer29

Redeemable Convertible Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2017
Temporary Equity Disclosure [Abstract]
Schedule of Redeemable Convertible Preferred Stock	Redeemable convertible preferred stock consists of the following as of December 31, 2016 and as of immediately prior to the automatic conversion of redeemable convertible preferred stock into common stock (in thousands, except share amounts): December 31, 2016 Shares Shares Liquidation Original Issuance Carrying Value Series A Preferred 14,742 14,736 $ 1,327 $ 1,327 $ 5,777 Series B Preferred 63,339 63,329 12,288 12,288 32,693 Series C Preferred 47,137 47,132 9,899 9,899 24,539 Series D and D-1 Preferred 7,537,780 7,537,753 16,063 16,063 70,904 Series E Preferred 3,627,391 3,627,381 8,102 8,102 34,306 Series E-1 Preferred 626,195 333,333 2,000 2,000 3,524 Series E-2 Preferred 257,756 257,756 1,933 1,933 5,171 Series F Preferred 3,242,963 3,242,957 30,000 30,000 29,201 Series G Preferred 3,344,544 3,344,540 79,379 79,379 77,739 Total 18,761,847 18,468,917 $ 160,991 $ 160,991 $ 283,854

Preferred and Common Stock Wa30

Preferred and Common Stock Warrants (Tables)	12 Months Ended
	Dec. 31, 2017
Warrants and Rights Note Disclosure [Abstract]
Schedule of Preferred Stock Warrants Outstanding	The redeemable convertible preferred stock warrants outstanding prior to the IPO were as follows: Issuance Date Exercisable Date Expiration Shares Exercise Price Per Share Series E-1 warrants 10/24/2012 10/24/2012 10/24/2019 292,862 $ 6.00
Schedule of Fair Value Assumptions	The following table summarizes the assumptions used to determine the fair value of the Company’s redeemable convertible preferred stock warrants as of December 31, 2016 : December 31, 2016 Fair value of Series E-1 redeemable convertible preferred stock $20.46 Risk-free interest rate 0.7% Expected term 0.8 Expected volatility 61% Dividend yield —%

Common Stock Reserved for Iss31

Common Stock Reserved for Issuance (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Common Stock Reserved	As of December 31, 2017 , common stock reserved, on an as-if converted basis for issuance are as follows: Shares Reserved for future issuance under equity award plans 3,732,143 Common stock options outstanding 9,313,633 Restricted stock units outstanding 4,216,001 Common stock warrants outstanding 83,237 Total common stock reserved for issuance 17,345,014

Equity Award Plans (Tables)

Equity Award Plans (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Option Activity under the Plan	The following table summarizes option activity under the Plan and related information (in thousands, except share, per share and contractual life amounts): Options Outstanding Shares Number Weighted- Weighted- Aggregate Balance—December 31, 2015 833,319 8,352,659 $7.72 8.4 $ 93,575 Additional shares authorized 2,030,000 — — Options granted (2,319,385 ) 2,319,385 $17.42 Restricted stock units granted (1,042,000 ) — — Options forfeited 653,434 (653,434 ) $10.10 Options exercised — (431,095 ) $2.53 Balance—December 31, 2016 155,368 9,587,515 $10.13 8.0 $ 61,865 Additional shares authorized 5,926,134 — — Options granted (549,236 ) 549,236 $20.05 Restricted stock units granted (2,354,793 ) — — Restricted stock units forfeited 37,415 — — Options forfeited 517,255 (517,255 ) $14.58 Options exercised — (305,863 ) $5.32 Balance—December 31, 2017 3,732,143 9,313,633 $10.63 7.2 $ 198,012 Options vested and expected to vest—December 31, 2017 9,313,633 $10.63 7.2 $ 198,012 Options vested and exercisable—December 31, 2017 5,675,785 $8.40 6.5 $ 133,316
Schedule of RSU Activity under the Plan	The following table summarizes RSU activity under the Plan and related information (in thousands, except share, per share and contractual life amounts): RSUs Outstanding Number Weighted- Weighted- Aggregate Balance—December 31, 2015 1,069,526 $ 9.06 2.7 $ 20,235 RSUs granted 1,042,000 $ 19.44 RSUs vested (212,903 ) $ 8.39 Balance—December 31, 2016 1,898,623 $ 14.83 1.7 $ 30,720 RSUs granted 2,354,793 $ 25.20 RSUs forfeited (37,415 ) $ 20.44 Balance—December 31, 2017 4,216,001 $ 20.57 1.7 $ 134,448 RSUs vested and expected to vest—December 31, 2017 4,216,001 $ 20.57 1.7 $ 134,448
Schedule of Stock-based Compensation Expense for Employees and Non-Employees	Stock-based compensation expense for both employees and non-employees included in the accompanying consolidated statements of operations is as follows (in thousands): Year Ended December 31, 2015 2016 2017 Cost of revenue: Product $ 16 $ 30 $ 103 Maintenance and professional services 391 1,123 2,291 Research and development 1,101 2,311 6,213 Sales and marketing 2,245 8,084 14,451 General and administrative 4,959 5,286 19,538 Total $ 8,712 $ 16,834 $ 42,596
Schedule of Assumptions Used to Determine Grant Date Fair Value of Employee Stock Options	The assumptions used to determine the grant date fair value of employee stock options and ESPP purchase rights for the periods presented are as follows: Year Ended December 31, 2015 2016 2017 Employee Stock Options Fair value of common stock $8.32 – $18.92 $15.78 – $21.56 $16.73 – $31.16 Risk-free interest rate 0.0% – 2.0% 1.2% – 2.1% 1.9% – 2.2% Expected term (in years) 0.1 – 6.2 6.0 – 8.1 6.0 – 6.1 Volatility 24% – 50% 47% – 51% 46% – 49% Dividend yield —% —% —% Employee Stock Purchase Plan Fair value of common stock $— $— $6.86 Risk-free interest rate —% —% 1.4% Expected term (in years) 0 0 0.52 Volatility —% —% 29.9% Dividend yield —% —% —%

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of loss before provision for income taxes, domestic and foreign	The components of loss before provision for income taxes are as follows (in thousands): Year Ended December 31, 2016 2017 Domestic $ (76,105 ) $ (92,777 ) Foreign 2,581 3,411 Total $ (73,524 ) $ (89,366 )
Schedule of components of income tax expense	The provision for income taxes consists of the following (in thousands): Year Ended December 31, 2016 2017 Current Federal $ 4 $ 17 State 66 50 Foreign 1,273 1,788 Total current 1,343 1,855 Deferred Foreign (95 ) (16 ) Total deferred $ (95 ) $ (16 ) Total $ 1,248 $ 1,839
Schedule of deferred tax assets and liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows (in thousands): December 31, 2016 2017 Deferred tax assets: Federal and state net operating losses $ 50,312 $ 43,410 Research/other credits 862 1,060 Non-deductible and accrued expenses 5,932 4,485 Deferred revenue 12,590 10,438 Stock options 3,400 9,507 Other 1,003 609 Gross deferred tax assets 74,099 69,509 Valuation allowance (73,939 ) (69,320 ) Net deferred tax assets 160 189 Deferred tax liabilities: Property and equipment — (13 ) Net deferred tax liabilities — (13 ) Total $ 160 $ 176
Schedule of effective income tax rate reconciliation	Reconciliation of the statutory federal income tax to the Company’s effective tax (in thousands): Year Ended December 31, 2016 2017 Tax at federal statutory rate $ (24,998 ) $ (30,385 ) State, net of federal benefit 61 60 Stock options 3,225 4,097 Non-deductible warrant expenses (365 ) 272 Tax Reform federal rate change — 36,460 Change in valuation allowance 22,385 (10,512 ) Other 940 1,847 Total $ 1,248 $ 1,839
Schedule of Unrecognized Tax Benefits Roll Forward	A reconciliation of the gross unrecognized tax benefit is as follows (in thousands): Year Ended December 31, 2016 2017 Unrecognized tax benefits at the beginning of the period $ 254 $ 1,050 Additions for tax positions taken in prior years 185 248 Additions for tax positions taken in current year 611 845 Settlements with taxing authorities — (416 ) Unrecognized tax benefits at the end of the period $ 1,050 $ 1,727

Net Loss Per Share (Tables)

Net Loss Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss Per Share	The following table presents the computation of basic and diluted net loss per share attributable to common stockholders (in thousands, except share and per share amounts): Year Ended December 31, 2015 2016 2017 Net loss $ (27,260 ) $ (74,774 ) $ (91,205 ) Deemed dividend on the conversion of Series G redeemable convertible preferred stock — — 12,810 Net loss attributable to common stockholders $ (27,260 ) $ (74,774 ) $ (104,015 ) Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted 4,121,852 5,609,187 11,405,356 Net loss per share attributable to common stockholders, basic and diluted $ (6.61 ) $ (13.33 ) $ (9.12 )
Schedule of Securities Excluded from Computation of Diluted Net Loss Per Share	The following securities were excluded from the computation of diluted net loss per share attributable to common stockholders for the periods presented because their inclusion would reduce the net loss per share. Year Ended December 31, 2015 2016 2017 Options to purchase common stock 8,351,589 9,587,572 9,313,633 Unvested early exercised common shares 474,148 329,957 146,468 Unvested restricted stock units 1,069,524 1,898,621 4,216,001 Shares estimated under ESPP — — 220,721 Warrants to purchase common stock 233,023 233,023 83,237 Redeemable convertible preferred stock 24,620,991 24,788,362 — Warrants to purchase redeemable convertible preferred stock 292,862 292,862 —

Segment Information (Tables)

Segment Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Revenue by Geographic Area	Revenue by geographic area is attributed based on the billing address of the customer and is as follows (in thousands): Year Ended December 31, 2015 2016 2017 Revenue: Americas United States $ 99,519 $ 133,615 $ 162,479 Other Americas 3,865 4,949 6,176 Total Americas 103,384 138,564 168,655 Europe, Middle East, and Africa (“EMEA”) 15,023 18,918 36,300 Asia Pacific and Japan (“APJ”) 7,552 9,359 15,916 Total revenue $ 125,959 $ 166,841 $ 220,871
Schedule of Long-lived Assets by Geographical Area	Long-lived assets, net by geographic area are attributed based on legal entity structure and are as follows (in thousands): December 31, 2016 2017 Long-lived assets, net: United States $ 21,141 $ 18,989 Israel 3,051 3,453 Other 344 818 Total long-lived assets, net $ 24,536 $ 23,260

Description of Business and S36

Description of Business and Summary of Significant Accounting Policies - Company Background (Details)	12 Months Ended
	Dec. 31, 2017product
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of products	3

Description of Business and S37

Description of Business and Summary of Significant Accounting Policies - IPO Transaction (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Subsidiary, Sale of Stock [Line Items]
Offering costs		$ 4,245	$ 8	$ 0
IPO
Subsidiary, Sale of Stock [Line Items]
Number of shares issued in IPO (in shares)	6,072,000
IPO price per share (in usd per share)	$ 22
Consideration received from IPO	$ 124,200
Offering costs	$ 4,500
Common stock
Subsidiary, Sale of Stock [Line Items]
Shares converted into common stock (in shares)	25,370,616	24,844,349

Description of Business and S38

Description of Business and Summary of Significant Accounting Policies - Stock Split (Details)	Oct. 16, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Reverse stock split conversion ratio	0.5

Description of Business and S39

Description of Business and Summary of Significant Accounting Policies - Segment Information (Details)	12 Months Ended
	Dec. 31, 2017segmentbusiness_activity
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of business activities | business_activity	1
Number of segments | segment	1

Description of Business and S40

Description of Business and Summary of Significant Accounting Policies - Concentrations (Details) - manufacturer	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration Risk [Line Items]
Number of contract manufacturers	1
Customer Concentration Risk | Accounts receivable | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	32.00%	20.00%
Customer Concentration Risk | Accounts receivable | Customer Two
Concentration Risk [Line Items]
Concentration risk percentage	17.00%	17.00%
Customer Concentration Risk | Accounts receivable | Customer Three
Concentration Risk [Line Items]
Concentration risk percentage		16.00%
Customer Concentration Risk | Accounts receivable | Customer Four
Concentration Risk [Line Items]
Concentration risk percentage		12.00%
Customer Concentration Risk | Total revenue | Customer One
Concentration Risk [Line Items]
Concentration risk percentage	30.00%	24.00%	14.00%
Customer Concentration Risk | Total revenue | Customer Two
Concentration Risk [Line Items]
Concentration risk percentage	21.00%	14.00%	11.00%
Customer Concentration Risk | Total revenue | Customer Three
Concentration Risk [Line Items]
Concentration risk percentage	17.00%	13.00%	10.00%

Description of Business and S41

Description of Business and Summary of Significant Accounting Policies - Foreign Currency, Restricted Cash, and Deferred Offering Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Net foreign currency remeasurement losses	$ 100	$ 900	$ 400
Restricted cash, current	200	200
Restricted cash, noncurrent	4,146	4,011
Deferred offering costs		$ 1,400
Deferred offering costs recognized through IPO completion	$ 4,500

Description of Business and S42

Description of Business and Summary of Significant Accounting Policies - Property and Equipment, Product Warranty, and Revenue Recognition (Details)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Standard product warranty period	90 days
Maximum support and maintenance contractual service period (up to)	5 years
Minimum
Property, Plant and Equipment [Line Items]
Useful life	3 years
Extended product warranty period	1 year
Typical support and maintenance contractual service period	1 year
Maximum
Property, Plant and Equipment [Line Items]
Useful life	5 years
Extended product warranty period	5 years
Typical support and maintenance contractual service period	3 years
Demonstration units
Property, Plant and Equipment [Line Items]
Useful life	3 years

Description of Business and S43

Description of Business and Summary of Significant Accounting Policies - Redeemable Convertible Preferred and Common Stock Warrant Liabilities (Details) - Common Stock Warrants - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Class of Warrant or Right [Line Items]
Warrants to purchase common stock (in shares)	83,237	233,023
Exercise Price Per Share (in dollars per share)		$ 6.62
Warrants to purchase common stock (in shares)	149,786
Shares issued, price per share (in dollars per share)	$ 25.28
Shares issued for warrant exercise (in shares)	111,147

Description of Business and S44

Description of Business and Summary of Significant Accounting Policies - Customer Deposits and Advertising Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Customer deposits	$ 1,008	$ 718
Advertising expenses	$ 430	$ 291	$ 7

Description of Business and S45

Description of Business and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle		$ 34
Deferred tax assets, valuation allowance	$ 69,320	73,939
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle		34
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred tax assets		2,300
Deferred tax assets, valuation allowance		2,300
Accounting Standards Update 2016-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle		$ 34

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financial Assets
Marketable securities	$ 123,384
Commercial paper
Financial Assets
Marketable securities	40,610
Corporate debt securities
Financial Assets
Marketable securities	58,948
U.S. government securities
Financial Assets
Marketable securities	23,826
Recurring | Level 1
Financial Assets
Cash and cash equivalents	63,009	$ 79,665
Restricted cash	4,348	4,212
Total financial assets	67,357	83,877
Financial Liabilities
Warrant liabilities	0	0
Recurring | Level 1 | Debt Securities
Financial Assets
Marketable securities	0	0
Recurring | Level 1 | Commercial paper
Financial Assets
Marketable securities	0	0
Recurring | Level 1 | Corporate debt securities
Financial Assets
Marketable securities	0	0
Recurring | Level 1 | U.S. government securities
Financial Assets
Marketable securities	0	0
Recurring | Level 1 | Cash
Financial Assets
Cash and cash equivalents	24,526	42,499
Recurring | Level 1 | Money market accounts
Financial Assets
Cash and cash equivalents	38,483	37,166
Recurring | Level 2
Financial Assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Total financial assets	123,384	0
Financial Liabilities
Warrant liabilities	0	0
Recurring | Level 2 | Debt Securities
Financial Assets
Marketable securities	123,384	0
Recurring | Level 2 | Commercial paper
Financial Assets
Marketable securities	40,610	0
Recurring | Level 2 | Corporate debt securities
Financial Assets
Marketable securities	58,948	0
Recurring | Level 2 | U.S. government securities
Financial Assets
Marketable securities	23,826	0
Recurring | Level 2 | Cash
Financial Assets
Cash and cash equivalents	0	0
Recurring | Level 2 | Money market accounts
Financial Assets
Cash and cash equivalents	0	0
Recurring | Level 3
Financial Assets
Cash and cash equivalents	0	0
Restricted cash	0	0
Total financial assets	0	0
Financial Liabilities
Warrant liabilities	0	4,874
Recurring | Level 3 | Debt Securities
Financial Assets
Marketable securities	0	0
Recurring | Level 3 | Commercial paper
Financial Assets
Marketable securities	0	0
Recurring | Level 3 | Corporate debt securities
Financial Assets
Marketable securities	0	0
Recurring | Level 3 | U.S. government securities
Financial Assets
Marketable securities	0	0
Recurring | Level 3 | Cash
Financial Assets
Cash and cash equivalents	0	0
Recurring | Level 3 | Money market accounts
Financial Assets
Cash and cash equivalents	$ 0	$ 0

Fair Value Measurements - Activ

Fair Value Measurements - Activity for Warrant Liabilities (Details) - Warrant liabilities - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 4,874	$ 5,978
Revaluation of warrant liabilities	727	(1,104)
Reclassification of preferred stock warrants to common stock warrants upon IPO	(4,173)
Exercise of preferred stock warrants	(1,428)
Ending balance	$ 0	$ 4,874

Marketable Securities - Summary

Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 123,496
Unrealized Losses	(112)	$ 0	$ 0
Fair Value	123,384
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	40,610
Unrealized Losses	0
Fair Value	40,610
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	59,031
Unrealized Losses	(83)
Fair Value	58,948
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,855
Unrealized Losses	(29)
Fair Value	$ 23,826

Marketable Securities - Maturit

Marketable Securities - Maturities (Details) $ in Thousands	Dec. 31, 2017USD ($)
Amortized Cost
Due within one year	$ 83,419
Due between one and five years	40,077
Amortized Cost	123,496
Fair Value
Due within one year	83,374
Due between one and five years	40,010
Total	$ 123,384

Marketable Securities - Continu

Marketable Securities - Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2017USD ($)
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	$ 82,352
Less Than 12 Months, Unrealized Loss	(112)
Greater Than 12 Months, Fair Value	0
Greater Than 12 Months, Unrealized Loss	0
Total, Fair Value	82,352
Total, Unrealized Loss	(112)
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	58,581
Less Than 12 Months, Unrealized Loss	(83)
Greater Than 12 Months, Fair Value	0
Greater Than 12 Months, Unrealized Loss	0
Total, Fair Value	58,581
Total, Unrealized Loss	(83)
U.S. government securities
Schedule of Available-for-sale Securities [Line Items]
Less Than 12 Months, Fair Value	23,771
Less Than 12 Months, Unrealized Loss	(29)
Greater Than 12 Months, Fair Value	0
Greater Than 12 Months, Unrealized Loss	0
Total, Fair Value	23,771
Total, Unrealized Loss	$ (29)

Marketable Securities - Narrati

Marketable Securities - Narrative (Details)	12 Months Ended
	Dec. 31, 2017USD ($)
Investments, Debt and Equity Securities [Abstract]
Other than temporary impairment	$ 0

Property and Equipment, Net (De

Property and Equipment, Net (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 34,571	$ 30,948
Less: accumulated depreciation	(11,311)	(6,412)
Total property and equipment, net	23,260	24,536
Depreciation expense	6,068	3,610	$ 1,788
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment	18,617	18,158
Computer equipment and software
Property, Plant and Equipment [Line Items]
Total property and equipment	9,835	7,246
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment	3,577	3,609
Demonstration units
Property, Plant and Equipment [Line Items]
Total property and equipment	2,528	1,824
Construction in progress
Property, Plant and Equipment [Line Items]
Total property and equipment	$ 14	$ 111

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) $ in Thousands	1 Months Ended	12 Months Ended
	Oct. 31, 2015renewal_option	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Operating Leased Assets [Line Items]
Total property and equipment		$ 34,571	$ 30,948
Rent expense		5,600	5,300	$ 2,400
Purchase obligations		2,600
Leasehold improvements
Operating Leased Assets [Line Items]
Total property and equipment		18,617	$ 18,158
Corporate Office
Operating Leased Assets [Line Items]
Lease agreement	11 years
Number of operating leases | renewal_option	1
Lease renewal term	5 years
Lease rent free period	1 year
Incentive for tenant improvements		4,800
Corporate Office | Maximum
Operating Leased Assets [Line Items]
Incentive for tenant improvements		4,800
Corporate Office | Leasehold improvements
Operating Leased Assets [Line Items]
Total property and equipment		15,700
Contract manufacturer commitments
Operating Leased Assets [Line Items]
Contract manufacturer commitments		$ 6,000

Commitments and Contingencies54

Commitments and Contingencies - Future Minimum Lease Payments (Details) $ in Thousands	Dec. 31, 2017USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,018	$ 6,100
2,019	4,882
2,020	3,255
2,021	3,356
2,022	3,460
2023 and thereafter	14,254
Total	$ 35,307

Debt Agreements - Narrative (De

Debt Agreements - Narrative (Details)	Dec. 22, 2016USD ($)	Dec. 01, 2016USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Debt Instrument [Line Items]
Repayments of notes payable		$ 20,100,000	$ 7,500,000	$ 20,130,000	$ 172,000
Amortization of debt discount (premium)			300,000	700,000	$ 700,000
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding revolving line of credit			$ 0	$ 0
Line of Credit | Amended Loan and Security Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Percentage of qualified accounts receivable	80.00%
Face amount	$ 30,000,000
Maximum credit available for borrowing	$ 40,000,000
Quick ratio required	1.25
Monthly installments of principal	$ 625,000
Stated interest rate	3.25%
Additional payment at maturity	$ 825,000

Debt Agreements - Carrying Valu

Debt Agreements - Carrying Value of Notes Payable (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Less current portion	$ (7,245)	$ (7,163)
Non-current portion of notes payable	15,579	22,824
Notes Payable to Banks
Debt Instrument [Line Items]
Principal amount of notes payable	23,325	30,825
Unamortized debt discount	(501)	(838)
Net carrying amount of notes payable	22,824	29,987
Less current portion	(7,245)	(7,163)
Non-current portion of notes payable	$ 15,579	$ 22,824

Redeemable Convertible Prefer57

Redeemable Convertible Preferred Stock (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Shares Authorized (shares)		18,761,847
Shares Issued (shares)		18,468,917
Shares Outstanding (shares)	0	18,468,917	18,300,383	14,826,324
Liquidation Preference		$ 160,991
Original Issuance		160,991
Carrying Value	$ 0	$ 283,854	$ 279,913	$ 200,501
Series A Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		14,742
Shares Issued (shares)		14,736
Shares Outstanding (shares)		14,736
Liquidation Preference		$ 1,327
Original Issuance		1,327
Carrying Value		$ 5,777
Series B Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		63,339
Shares Issued (shares)		63,329
Shares Outstanding (shares)		63,329
Liquidation Preference		$ 12,288
Original Issuance		12,288
Carrying Value		$ 32,693
Series C Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		47,137
Shares Issued (shares)		47,132
Shares Outstanding (shares)		47,132
Liquidation Preference		$ 9,899
Original Issuance		9,899
Carrying Value		$ 24,539
Series D and D-1 Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		7,537,780
Shares Issued (shares)		7,537,753
Shares Outstanding (shares)		7,537,753
Liquidation Preference		$ 16,063
Original Issuance		16,063
Carrying Value		$ 70,904
Series E Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		3,627,391
Shares Issued (shares)		3,627,381
Shares Outstanding (shares)		3,627,381
Liquidation Preference		$ 8,102
Original Issuance		8,102
Carrying Value		$ 34,306
Series E-1 Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		626,195
Shares Issued (shares)		333,333
Shares Outstanding (shares)		333,333
Liquidation Preference		$ 2,000
Original Issuance		2,000
Carrying Value		$ 3,524
Series E-2 Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		257,756
Shares Issued (shares)		257,756
Shares Outstanding (shares)		257,756
Liquidation Preference		$ 1,933
Original Issuance		1,933
Carrying Value		$ 5,171
Series F Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		3,242,963
Shares Issued (shares)		3,242,957
Shares Outstanding (shares)		3,242,957
Liquidation Preference		$ 30,000
Original Issuance		30,000
Carrying Value		$ 29,201
Series G Preferred
Temporary Equity [Line Items]
Shares Authorized (shares)		3,344,544
Shares Issued (shares)		3,344,540
Shares Outstanding (shares)		3,344,540
Liquidation Preference		$ 79,379
Original Issuance		79,379
Carrying Value		$ 77,739

Redeemable Convertible Prefer58

Redeemable Convertible Preferred Stock - Narrative (Details) - $ / shares	Oct. 31, 2017	Dec. 31, 2017
Temporary Equity [Line Items]
Shares issued as stock dividend (in shares)	582,254
IPO
Temporary Equity [Line Items]
IPO price per share (in usd per share)	$ 22
Common stock
Temporary Equity [Line Items]
Shares converted into common stock (in shares)	25,370,616	24,844,349
Shares issued as stock dividend (in shares)		582,254

Preferred and Common Stock Wa59

Preferred and Common Stock Warrants - Redeemable Convertible Preferred Stock Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2017
Class of Warrant or Right [Line Items]
Fair value adjustment on conversion of warrants		$ 300
Conversion of preferred stock warrants to common stock warrants in connection with initial public offering		$ 4,200	$ 4,173
Fair value adjustment on exercise of warrants	$ 100
Series E-1 warrants
Class of Warrant or Right [Line Items]
Shares (in shares)		292,862
Exercise Price Per Share (in dollars per share)		$ 6
Redeemable Convertible Preferred Stock Warrant
Class of Warrant or Right [Line Items]
Shares issued, price per share (in dollars per share)	$ 25.12		$ 25.12
Shares issued for warrant exercise (in shares)			224,691

Preferred and Common Stock Wa60

Preferred and Common Stock Warrants - Fair Value Assumptions (Details) - Series E-1 warrants	12 Months Ended
	Dec. 31, 2016$ / shares
Class of Warrant or Right [Line Items]
Fair value of Series E-1 redeemable convertible preferred stock (in dollars per share)	$ 20.46
Risk-free interest rate	0.70%
Expected term	9 months 18 days
Expected volatility	61.00%
Dividend yield	0.00%

Preferred and Common Stock Wa61

Preferred and Common Stock Warrants - Common Stock Warrants (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Oct. 31, 2017	Dec. 31, 2016	Sep. 30, 2014
Class of Warrant or Right [Line Items]
IPO stated per share threshold (in dollars per share)				$ 17
Common Stock Warrants
Class of Warrant or Right [Line Items]
Warrants to purchase common stock (in shares)	83,237		233,023
Exercise price (in dollars per share)			$ 6.62
Warrants to purchase common stock (in shares)	149,786
Shares issued, price per share (in dollars per share)	$ 25.28
Shares issued for warrant exercise (in shares)	111,147
IPO
Class of Warrant or Right [Line Items]
IPO price per share (in usd per share)		$ 22

Common Stock Reserved for Iss62

Common Stock Reserved for Issuance (Details)	Dec. 31, 2017shares
Class of Stock [Line Items]
Common stock reserved for issuance (shares)	17,345,014
Common stock warrants
Class of Stock [Line Items]
Common stock reserved for issuance (shares)	83,237
Equity award plans
Class of Stock [Line Items]
Common stock reserved for issuance (shares)	3,732,143
Stock options | Common stock
Class of Stock [Line Items]
Common stock reserved for issuance (shares)	9,313,633
Restricted stock units
Class of Stock [Line Items]
Common stock reserved for issuance (shares)	4,216,001

Equity Award Plans - Narrative

Equity Award Plans - Narrative (Details) $ / shares in Units, $ in Millions	Oct. 31, 2017USD ($)shares	Oct. 31, 2017shares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)employee$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (shares)			17,345,014	17,345,014
Early exercises, compensation cost | $				$ 1.2	$ 2.3
Common stock, shares outstanding including early exercises (shares)			38,266,450	38,266,450	6,184,187
Number of shares available for grant (in shares)			3,732,143	3,732,143	155,368	833,319
Options grants in period, weighted average grant date fair value (in dollars per share) | $ / shares				$ 9.79	$ 8.24	$ 5.82
Aggregate intrinsic value of employee options exercised | $				$ 4.4	$ 6	$ 10
Unrecognized compensation cost related to unvested options | $			$ 25.8	$ 25.8
Option exercise price (in dollars per share) | $ / shares			$ 10.63	$ 10.63	$ 10.13	$ 7.72
Number of employees with separation agreements | employee					3
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option expiration period				10 years
Straight-line basis weighted-average amortization period				2 years 1 month 6 days
Equity award plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (shares)			3,732,143	3,732,143
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percent of market price		85.00%
Annual increase to shares available for future issuance (in shares)	800,000	800,000
Percentage of common stock outstanding annual increase to shares available for issuance	1.00%	1.00%
Number of shares available for grant (in shares)	800,000	800,000
Stock purchase offering period		6 months
Participants maximum percentage of annual salary	15.00%	15.00%
Shares purchased during period (in shares)				0
Unrecognized compensation cost | $			$ 1.1	$ 1.1
Straight-line basis weighted-average amortization period				4 months 24 days
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
Common stock reserved for issuance (shares)			4,216,001	4,216,001
Unrecognized compensation cost | $			$ 67.2	$ 67.2
Straight-line basis weighted-average amortization period				2 years 2 months 12 days
Restricted stock units outstanding (shares)			4,216,001	4,216,001	1,898,623	1,069,526
Award requisite service period				181 days
Stock options and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense | $	$ 21.2
CEO
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Incremental stock-based compensation cost over service period | $				$ 7.6
Incremental stock-based compensation expense | $			$ 6.5
2000 Stock Option and Incentive Plan | Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percent of market price				100.00%
Outstanding common stock ownership threshold, percentage				10.00%
Purchase price of common stock for executive officers that own more than 10%, percent of market price				110.00%
Option expiration period				10 years
2000 Stock Option and Incentive Plan | Stock options and RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period				4 years
2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares authorized to be added to the Plan (shares)	12,500,000	12,500,000
Annual increase to shares available for future issuance (in shares)	3,800,000	3,800,000
Percentage of common stock outstanding annual increase to shares available for issuance	5.00%	5.00%
2017 Equity Incentive Plan | Equity award plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance (shares)	3,800,000	3,800,000

Equity Award Plans - Option Act

Equity Award Plans - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
Balance beginning of the period (shares)	9,587,515	8,352,659
Options granted (shares)	549,236	2,319,385
Restricted stock units granted (shares)	2,354,793	1,042,000
Options forfeited (shares)	(517,255)	(653,434)
Options exercised (shares)	(305,863)	(431,095)
Balance end of the period (shares)	9,313,633	9,587,515	8,352,659
Weighted- Average Exercise Price
Balance beginning of the period (in dollars per share)	$ 10.13	$ 7.72
Options granted (in dollars per share)	20.05	17.42
Options forfeited (in dollars per share)	14.58	10.10
Options exercised (in dollars per share)	5.32	2.53
Balance end of the period (in dollars per share)	$ 10.63	$ 10.13	$ 7.72
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures
Shares available for grant (shares)	3,732,143	155,368	833,319
Additional shares authorized (shares)	5,926,134	2,030,000
Restricted stock units forfeited (shares)	37,415
Options vested and expected to vest at end of period (shares)	9,313,633
Options vested and exercisable at end of period (shares)	5,675,785
Options vested and expected to vest at end of period (in dollars per share)	$ 10.63
Options vested and exercisable at end of period (in dollars per share)	$ 8.40
Balance, Weighted-Average Remaining Contractual Life (Years)	7 years 2 months 12 days	8 years	8 years 4 months 24 days
Options vested and expected to vest at end of period, Weighted-Average Remaining Contractual Life (Years)	7 years 2 months 12 days
Options vested and exercisable, Weighted Average-Remaining Contractual Life (Years)	6 years 6 months
Balance, Aggregate Intrinsic Value	$ 198,012	$ 61,865	$ 93,575
Options vested and expected to vest at end of period, Aggregate Intrinsic Value	198,012
Options vested and exercisable at end of period, Aggregate Intrinsic Value	$ 133,316

Equity Award Plans - RSU Activi

Equity Award Plans - RSU Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Shares
RSUs granted (shares)	2,354,793	1,042,000
RSUs forfeited (shares)	(37,415)
RSUs
Number of Shares
Balance at beginning of period (shares)	1,898,623	1,069,526
RSUs granted (shares)	2,354,793	1,042,000
RSUs vested (shares)		(212,903)
RSUs forfeited (shares)	(37,415)
Balance at end of period (shares)	4,216,001	1,898,623	1,069,526
Weighted- Average Grant Date Fair Value Per Share
Balance at beginning of period (in dollars per share)	$ 14.83	$ 9.06
RSUs granted (in dollars per share)	25.20	19.44
RSUs vested (in dollars per share)		8.39
RSUs forfeited (in dollars per share)	20.44
Balance at end of period (in dollars per share)	$ 20.57	$ 14.83	$ 9.06
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures
RSUs vested and expected to vest at end of period (shares)	4,216,001
RSUs vested and expected to vest at end of period (in dollars per share)	$ 20.57
Balance, Weighted-Average Remaining Contractual Live (Years)	1 year 8 months 12 days	1 year 8 months 12 days	2 years 8 months 12 days
RSUs vested and expected to vest, Weighted-Average Remaining Contractual Life (Years)	1 year 8 months 12 days
Balance, Aggregate Intrinsic Value	$ 134,448	$ 30,720	$ 20,235
RSUs vested and expected to vest at end of period, Aggregate Intrinsic Value	$ 134,448

Equity Award Plans - Stock-Base

Equity Award Plans - Stock-Based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 42,596	$ 16,834	$ 8,712
Product
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	103	30	16
Maintenance and professional services
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	2,291	1,123	391
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	6,213	2,311	1,101
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	14,451	8,084	2,245
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 19,538	$ 5,286	$ 4,959

Equity Award Plans - Assumption

Equity Award Plans - Assumptions (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate, minimum	1.90%	1.20%	0.00%
Risk-free interest rate, maximum	2.20%	2.10%	2.00%
Volatility, minimum	46.00%	47.00%	24.00%
Volatility, maximum	49.00%	51.00%	50.00%
Dividend yield	0.00%	0.00%	0.00%
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in dollars per share)	$ 6.86	$ 0	$ 0
Risk-free interest rate	1.40%	0.00%	0.00%
Expected term (in years)	6 months 7 days	0 years	0 years
Volatility	29.90%	0.00%	0.00%
Dividend yield	0.00%	0.00%	0.00%
Minimum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years	6 years	1 month 6 days
Maximum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (in years)	6 years 1 month 6 days	8 years 1 month 6 days	6 years 2 months 12 days
Common stock | Minimum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in dollars per share)	$ 16.73	$ 15.78	$ 8.32
Common stock | Maximum | Employee Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of common stock (in dollars per share)	$ 31.16	$ 21.56	$ 18.92

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Domestic	$ (92,777)	$ (76,105)
Foreign	3,411	2,581
Loss before income taxes	$ (89,366)	$ (73,524)	$ (26,932)

Income Taxes - Schedule of Prov

Income Taxes - Schedule of Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current
Federal	$ 17	$ 4
State	50	66
Foreign	1,788	1,273
Total current	1,855	1,343
Deferred
Foreign	(16)	(95)
Total deferred	(16)	(95)
Total	$ 1,839	$ 1,250	$ 328

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Federal and state net operating losses	$ 43,410	$ 50,312
Research/other credits	1,060	862
Non-deductible and accrued expenses	4,485	5,932
Deferred revenue	10,438	12,590
Stock options	9,507	3,400
Other	609	1,003
Gross deferred tax assets	69,509	74,099
Valuation allowance	(69,320)	(73,939)
Net deferred tax assets	189	160
Deferred tax liabilities:
Property and equipment	(13)	0
Net deferred tax liabilities	(13)	0
Total	$ 176	$ 160

Income Taxes - Effective Income

Income Taxes - Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Tax at federal statutory rate	$ (30,385)	$ (24,998)
State, net of federal benefit	60	61
Stock options	4,097	3,225
Non-deductible warrant expenses	272	(365)
Tax Reform federal rate change	36,460	0
Change in valuation allowance	(10,512)	22,385
Other	1,847	940
Total	$ 1,839	$ 1,250	$ 328

Income Taxes - Narrative (Detai

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Tax reform federal rate change		$ 36,460	$ 0
Provisional undistributed accumulated earnings of foreign subsidiary		6,900
Income tax provision		$ 1,839	$ 1,250	$ 328
Effective tax rate		(2.10%)	(1.70%)
Increase (decrease) in valuation allowance		$ (4,600)	$ 25,000
Operating loss carryforward written off due to limitation		2,800
Undistributed earnings of foreign subsidiaries		6,900
Settlements with taxing authorities	$ 400	416	$ 0
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		180,100
Research and development tax credit carryforward | Federal
Operating Loss Carryforwards [Line Items]
Tax credit carryforward		700
Research and development tax credit carryforward | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Tax credit carryforward		500
California | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		22,000
Other states excluding California | State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards		$ 76,600

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits at the beginning of the period	$ 1,050	$ 1,050	$ 254
Additions for tax positions taken in prior years		248	185
Additions for tax positions taken in current year		845	611
Settlements with taxing authorities	$ (400)	(416)	0
Unrecognized tax benefits at the end of the period		$ 1,727	$ 1,050

Net Loss Per Share - Basic and

Net Loss Per Share - Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net loss	$ (91,205)	$ (74,774)	$ (27,260)
Deemed dividend on the conversion of Series G redeemable convertible preferred stock	12,810	0	0
Net loss attributable to common stockholders	$ (104,015)	$ (74,774)	$ (27,260)
Weighted-average shares used to compute net loss per share attributable to common stockholders, basic and diluted (in shares)	11,405,356	5,609,187	4,121,852
Net loss per share attributable to common stockholders, basic and diluted (in dollars per share)	$ (9.12)	$ (13.33)	$ (6.61)

Net Loss Per Share - Securities

Net Loss Per Share - Securities Excluded from Diluted Net Loss Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	9,313,633	9,587,572	8,351,589
Unvested early exercised common shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	146,468	329,957	474,148
Unvested restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	4,216,001	1,898,621	1,069,524
Shares estimated under ESPP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	220,721	0	0
Warrants to purchase | Common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	83,237	233,023	233,023
Warrants to purchase | Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	0	292,862	292,862
Redeemable convertible preferred stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from computation of diluted net loss per share (shares)	0	24,788,362	24,620,991

Employee Benefit Plans (Details

Employee Benefit Plans (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Estimated accrued severance benefits, noncurrent liability	$ 2,617,000	$ 2,033,000
Deposits in severance pay fund	$ 2,118,000	1,704,000
Company percent of match	50.00%
Employee percent contributed for company match	6.00%
Maximum matching dollar amount	$ 2,000
Matching contributions vesting percentage	100.00%
Company contributions to the 401(k)	$ 1,100,000	$ 1,000,000	$ 500,000

Segment Information - Narrative

Segment Information - Narrative (Details)	12 Months Ended
	Dec. 31, 2017segmentbusiness_activity
Segment Reporting [Abstract]
Number of business activities | business_activity	1
Single reportable segment	1
Single operating unit structure	1

Segment Information - Revenue (

Segment Information - Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 220,871	$ 166,841	$ 125,959
Total Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	168,655	138,564	103,384
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	162,479	133,615	99,519
Other Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	6,176	4,949	3,865
Europe, Middle East, and Africa (“EMEA”)
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	36,300	18,918	15,023
Asia Pacific and Japan (“APJ”)
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 15,916	$ 9,359	$ 7,552

Segment Information - Long-live

Segment Information - Long-lived Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, net	$ 23,260	$ 24,536
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, net	18,989	21,141
Israel
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, net	3,453	3,051
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, net	$ 818	$ 344

Related Party Transactions (Det

Related Party Transactions (Details) - Affiliated Entity	12 Months Ended
	Dec. 31, 2017USD ($)director	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)
Company A
Related Party Transaction [Line Items]
Number of directors who previously served as executive of related party company | director	1
Payments to related party	$ 157,000	$ 591,000	$ 77,000
Payments received from related party	$ 1,000	294,000	496,000
Company B
Related Party Transaction [Line Items]
Number of directors who previously served as executive of related party company | director	1
Payments to related party	$ 300,000	$ 200,000	$ 0