CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Restricted Stock Awards	Restricted Stock Awards Common Stock	Restricted Stock Awards Additional Paid-in Capital
Redeemable convertible preferred stock, shares outstanding at of beginning period (in shares) at Dec. 31, 2016	34,186,000
Redeemable convertible preferred stock, outstanding at beginning of period at Dec. 31, 2016	$ 79,528
Temporary Equity
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)	11,774,000
Issuance of redeemable convertible preferred stock, net of issuance costs	$ 52,346
Accretion of redeemable convertible preferred stock	$ 143
Redeemable convertible preferred stock, shares outstanding at end of period (in shares) at Dec. 31, 2017	45,960,000
Redeemable convertible preferred stock, outstanding at end of period at Dec. 31, 2017	$ 132,017
Common stock, shares outstanding at beginning of period (in shares) at Dec. 31, 2016		14,233,000
Stockholders' equity (deficit) at beginning of period at Dec. 31, 2016	(52,907)	$ 14	$ 10,452	$ (63,373)
Stockholders' Equity
Accretion of redeemable convertible preferred stock	$ (143)		(143)
Issuance of common stock upon exercise of warrants (in shares)	361,425	361,000
Issuance of common stock upon exercise of warrants	$ 286	$ 1	285
Conversion of redeemable convertible preferred stock to common stock	$ 0
Issuance of common stock upon exercise of stock options, net (in shares)	1,372,000	1,372,000
Issuance of common stock upon exercise of stock options, net	$ 1,069	$ 1	1,068
Issuance of stock awards (in shares)						1,064,000
Issuance of stock awards					$ 0	$ 1	$ (1)
Stock-based compensation expense	2,145		2,145
Net loss	(16,858)			(16,858)
Common stock, shares outstanding at end of period (in shares) at Dec. 31, 2017		17,030,000
Stockholders' equity (deficit) at end of period at Dec. 31, 2017	$ (66,408)	$ 17	13,806	(80,231)
Temporary Equity
Issuance of redeemable convertible preferred stock, net of issuance costs (in shares)	12,655,000
Issuance of redeemable convertible preferred stock, net of issuance costs	$ 104,750
Accretion of redeemable convertible preferred stock	$ 162
Redeemable convertible preferred stock, shares outstanding at end of period (in shares) at Dec. 31, 2018	58,615,000
Redeemable convertible preferred stock, outstanding at end of period at Dec. 31, 2018	$ 236,929
Stockholders' Equity
Accretion of redeemable convertible preferred stock	$ (162)		(162)
Issuance of common stock upon exercise of warrants (in shares)	0
Conversion of redeemable convertible preferred stock to common stock	$ 0
Issuance of common stock upon exercise of stock options, net (in shares)	1,454,000	1,415,000
Issuance of common stock upon exercise of stock options, net	$ 1,658	$ 2	1,656
Cancellation of restricted stock awards (in shares)		(754,000)
Cancellation of restricted stock awards		$ (1)	1
Stock-based compensation expense	6,488		6,488
Net loss	(33,382)			(33,382)
Common stock, shares outstanding at end of period (in shares) at Dec. 31, 2018		17,691,000
Stockholders' equity (deficit) at end of period at Dec. 31, 2018	(91,806)	$ 18	21,789	(113,613)
Temporary Equity
Accretion of redeemable convertible preferred stock	$ 96
Conversion of redeemable convertible preferred stock to common stock (in shares)	(58,615,000)
Conversion of redeemable convertible preferred stock to common stock	$ (237,025)
Redeemable convertible preferred stock, shares outstanding at end of period (in shares) at Dec. 31, 2019	0
Redeemable convertible preferred stock, outstanding at end of period at Dec. 31, 2019	$ 0
Stockholders' Equity
Accretion of redeemable convertible preferred stock	$ (96)		(96)
Issuance of common stock upon exercise of warrants (in shares)	90,000	90,000
Issuance of common stock upon exercise of warrants	$ 60		60
Conversion of redeemable convertible preferred stock to common stock (in shares)		58,615,000
Conversion of redeemable convertible preferred stock to common stock	237,025	$ 59	236,966
Issuance of common stock upon IPO (in shares)		14,590,000
Issuance of common stock upon IPO, net of issuance costs	$ 377,501	$ 14	377,487
Issuance of common stock upon exercise of stock options, net (in shares)	2,766,000	2,767,000
Issuance of common stock upon exercise of stock options, net	$ 3,096	$ 2	3,094
Issuance of stock awards (in shares)		601,000				982,000
Issuance of stock awards	0	$ 1	(1)		$ 0	$ 1	$ (1)
Tax withholding on releasing of restricted stock units (in shares)		(35,000)
Tax withholding on releasing of equity awards	(1,035)		(1,035)
Stock-based compensation expense	33,204		33,204
Net loss	(55,270)			(55,270)
Common stock, shares outstanding at end of period (in shares) at Dec. 31, 2019		95,301,000
Stockholders' equity (deficit) at end of period at Dec. 31, 2019	$ 507,364	$ 95	$ 671,467	$ (164,198)