Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) shares in Thousands	Total	Initial Public Offering	At-the-Market Offerings	Convertible Preferred Stock	Common Stock	Common Stock Initial Public Offering	Common Stock At-the-Market Offerings	Additional Paid-in Capital	Additional Paid-in Capital Initial Public Offering	Additional Paid-in Capital At-the-Market Offerings	Treasury Stock	Accumulated Other Comprehensive Loss	Accumulated Deficit
Balance at Dec. 31, 2016	$ (193,824,000)							$ 26,005,000					$ (219,829,000)
Balance, Shares at Dec. 31, 2016				80,844
Balance at Dec. 31, 2016				$ 213,180,000
Balance, Shares at Dec. 31, 2016					4,819
Issuance of common stock upon exercise of stock options	2,087,000				$ 1,000			2,086,000
Issuance of common stock upon exercise of stock options, Shares					963
Share repurchases	(671,000)										$ (671,000)
Share repurchases, Shares					(92)
Vesting of early exercised stock options	62,000							62,000
Stock-based compensation expense	10,953,000							10,953,000
Issuance of common stock pursuant to an acquisition, Shares					108
Issuance of common stock shares upon exercise of common and preferred warrants, Shares					2,165
Issuance of common stock, net of issuance costs		$ 131,646,000				$ 1,000			$ 131,645,000
Issuance of common stock, net of issuance costs, Shares						10,350
Conversion of preferred stock into common stock pursuant to an initial public offering	213,180,000			$ (213,180,000)	$ 8,000			213,172,000
Conversion of preferred stock into common stock pursuant to an initial public offering, Shares				(80,844)	80,844
Reclassification of preferred stock warrants liability to additional paid-in-capital upon conversion to common stock warrants	52,355,000							52,355,000
Unrealized gain (loss) on short-term investments	0
Net loss	(63,509,000)												(63,509,000)
Balance at Dec. 31, 2017	152,279,000				$ 10,000			436,278,000			(671,000)		(283,338,000)
Balance, Shares at Dec. 31, 2017					99,157
Share repurchases, Shares					(9)
Vesting of early exercised stock options	239,000							239,000
Issuance of common stock pursuant to equity incentive plans, net of taxes	25,034,000				$ 1,000			25,033,000
Issuance of common stock pursuant to equity incentive plans, net of taxes, Shares					10,481
Issuance of common stock pursuant to exercise of common stock warrants, net, Shares					141
Stock-based compensation expense	37,674,000							37,674,000
Cumulative effect change in accounting principle | Accounting Standards Update 2016-16	(40,000)												(40,000)
Cumulative effect change in accounting principle | Accounting Standards Update 2014-09	38,339,000												38,339,000
Unrealized gain (loss) on short-term investments	(17,000)											$ (17,000)
Net loss	(8,857,000)												(8,857,000)
Balance at Dec. 31, 2018	244,651,000				$ 11,000			499,224,000			(671,000)	(17,000)	(253,896,000)
Balance, Shares at Dec. 31, 2018					109,770
Share repurchases, Shares					(2)
Vesting of early exercised stock options	86,000							86,000
Issuance of common stock pursuant to equity incentive plans, net of taxes	28,182,000				$ 1,000			28,181,000
Issuance of common stock pursuant to equity incentive plans, net of taxes, Shares					6,169
Stock-based compensation expense	85,175,000							85,175,000
Issuance of common stock pursuant to an acquisition	69,684,000							69,684,000
Issuance of common stock pursuant to an acquisition, Shares					571
Issuance of common stock, net of issuance costs			$ 330,539,000							$ 330,539,000
Issuance of common stock, net of issuance costs, Shares							3,389
Unrealized gain (loss) on short-term investments	17,000											17,000
Foreign currency translation adjustment	29,000											29,000
Net loss	(59,937,000)												(59,937,000)
Balance at Dec. 31, 2019	$ 698,426,000				$ 12,000			$ 1,012,889,000			$ (671,000)	$ 29,000	$ (313,833,000)
Balance, Shares at Dec. 31, 2019					119,897