CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total		Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjustment	Additional Paid-In Capital	Additional Paid-In Capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjustment	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Beginning Balance at Dec. 31, 2017	$ 40,043			$ 1		$ 217,594		$ 19		$ (177,571)
Beginning Balance (Accounting Standards Update 2017-09) at Dec. 31, 2017			$ 0		$ 0		$ (43)		$ 0		$ 43
Begining balance, Shares at Dec. 31, 2017				101,383,000
Issuance of common stock in connection with initial public offering, net	225,336			$ 0		225,336		0		0
Issuance of common stock in connection with initial public offering, net, Shares				20,583,000
Common stock issued upon vesting of restricted stock units	(25,807)			$ 0		(25,807)		0		0
Common stock issued upon vesting of restricted stock units, Shares				3,771,000
Common stock issued upon stock option exercise	494			$ 0		494		0		0
Common stock issued upon stock option exercise, Shares				82,000
Repurchase of common stock	(16)			$ 0		(16)		0		0
Repurchase of common stock, Shares				(1,159)
Stock-based compensation expense	134,379			$ 0		134,379		0		0
Comprehensive income (loss)	(306)	[1]		0		0		(306)		0
Net loss	(154,740)			0		0		0		(154,740)
Ending balance at Dec. 31, 2018	219,383			$ 1		551,937		(287)		(332,268)
Ending balance (ASC 842) at Dec. 31, 2018			$ 3,411		$ 0		$ 0		$ 0		$ 3,411
Ending balance, Shares at Dec. 31, 2018				125,818,000
Common stock issued upon vesting of restricted stock units	0			$ 0		0		0		0
Common stock issued upon vesting of restricted stock units, Shares				3,661,000
Common stock issued upon stock option exercise	47,678			$ 0		47,678		0		0
Common stock issued upon stock option exercise, Shares				3,733,000
Common stock issued in connection with acquisitions	36,204			$ 0		36,204		0		0
Common stock issued in connection with acquisitions, shares				2,320,000
Common stock issued under employee stock purchase plan	5,344			$ 0		5,344		0		0
Common stock issued under employee stock purchase plan, shares				506,000
Stock-based compensation expense	63,748			$ 0		63,748		0		0
Comprehensive income (loss)	(157)	[1]		0		0		(157)		0
Other	232			$ 0		232		0		0
Other, shares				16,000
Net loss	(73,859)			$ 0		0		0		(73,859)
Ending balance at Dec. 31, 2019	301,984			$ 1		705,143		(444)		(402,716)
Ending balance, Shares at Dec. 31, 2019				136,054,000
Common stock issued upon vesting of restricted stock units	0			$ 0		0		0		0
Common stock issued upon vesting of restricted stock units, Shares				4,115,000
Common stock issued upon stock option exercise	$ 42,172			$ 0		42,172		0		0
Common stock issued upon stock option exercise, Shares	3,088,076			3,088,000
Common stock issued under employee stock purchase plan	$ 6,719			$ 0		6,719		0		0
Common stock issued under employee stock purchase plan, shares				563,000
Stock-based compensation expense	81,410			$ 0		81,410		0		0
Comprehensive income (loss)	5,652	[1]		0		0		5,652		0
Net loss	(91,581)			0		0		0		(91,581)
Ending balance at Dec. 31, 2020	$ 346,356			$ 1		$ 835,444		$ 5,208		$ (494,297)
Ending balance, Shares at Dec. 31, 2020				143,820,000

[1] Net of tax effect which was not material.