CONDENSED CONSOLIDATED STATEMENTS OF REDEEMABLE CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS’ EQUITY (DEFICIT) (unaudited) - USD ($) shares in Thousands, $ 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	Restricted stock units Common Stock
Redeemable convertible preferred stock, shares outstanding at of beginning period (in shares) at Dec. 31, 2018	58,615
Redeemable convertible preferred stock, outstanding at beginning of period at Dec. 31, 2018	$ 236,929
Temporary Equity
Accretion of redeemable convertible preferred stock	$ 41
Redeemable convertible preferred stock, shares outstanding at end of period (in shares) at Mar. 31, 2019	58,615
Redeemable convertible preferred stock, outstanding at end of period at Mar. 31, 2019	$ 236,970
Common stock, shares outstanding at beginning of period (in shares) at Dec. 31, 2018		17,691
Stockholders' equity (deficit) at beginning of period at Dec. 31, 2018	(91,806)	$ 18	$ 21,789	$ (113,613)
Stockholders' Equity
Accretion of redeemable convertible preferred stock	(41)		(41)
Issuance of common stock upon exercise of stock options (in shares)		454
Issuance of common stock upon exercise of stock options	314		314
Issuance of stock awards (in shares)		491				982
Issuance of stock awards	0	$ 1	(1)		$ 0	$ 1	$ (1)
Stock-based compensation expense	5,526		5,526
Net loss	(14,371)			(14,371)
Common stock, shares outstanding at end of period (in shares) at Mar. 31, 2019		19,618
Stockholders' equity (deficit) at end of period at Mar. 31, 2019	$ (95,693)	$ 20	27,586	(123,299)
Redeemable convertible preferred stock, shares outstanding at of beginning period (in shares) at Dec. 31, 2019	0
Redeemable convertible preferred stock, outstanding at beginning of period at Dec. 31, 2019	$ 0
Temporary Equity
Accretion of redeemable convertible preferred stock	$ 0
Redeemable convertible preferred stock, shares outstanding at end of period (in shares) at Mar. 31, 2020	0
Redeemable convertible preferred stock, outstanding at end of period at Mar. 31, 2020	$ 0
Common stock, shares outstanding at beginning of period (in shares) at Dec. 31, 2019		95,301
Stockholders' equity (deficit) at beginning of period at Dec. 31, 2019	$ 507,364	$ 95	671,467	(164,198)
Stockholders' Equity
Issuance of common stock upon exercise of stock options (in shares)	1,247	1,247
Issuance of common stock upon exercise of stock options	$ 1,722	$ 1	1,721
Issuance of stock awards (in shares)								1,120
Issuance of stock awards	0	$ 1	(1)
Tax withholding on releasing of restricted stock units (in shares)		(375)
Tax withholding on releasing of stock awards	(10,564)		(10,564)
Stock-based compensation expense	8,339		8,339
Net loss	(5,573)			(5,573)
Common stock, shares outstanding at end of period (in shares) at Mar. 31, 2020		97,293
Stockholders' equity (deficit) at end of period at Mar. 31, 2020	$ 501,288	$ 97	$ 670,962	$ (169,771)