Consolidated Statements of Changes in Redeemable Convertible Preferred Stock and Stockholders' Equity/(Deficit) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Redeemable convertible preferred stock beginning balance (in shares) at Dec. 31, 2017	0
Redeemable convertible preferred stock beginning balance at Dec. 31, 2017	$ 0
Redeemable convertible preferred stock ending balance (in shares) at Dec. 31, 2018	0
Redeemable convertible preferred stock ending balance at Dec. 31, 2018	$ 0
Balance, beginning of period (in shares) at Dec. 31, 2017		81,468,891
Balance, beginning of period at Dec. 31, 2017	235,430	$ 81	$ 364,352	$ (129,003)	$ 0
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to employee stock purchase plan (in shares)		425,228
Issuance of common stock pursuant to employee stock purchase program	6,588	$ 1	6,587
Issuance of common stock pursuant to exercise of stock options (in shares)		3,203,528
Issuance of common stock pursuant to exercise of stock options	16,820	$ 3	16,817
Issuance of common stock pursuant to settlement restricted stock units (in shares)		306,079
Issuance of common stock pursuant to restricted stock units	0	$ 0	0
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(88,721)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(1,426)	$ 0	(1,426)
Issuance of common stock, net (in shares)		4,836,336
Issuance of common stock, net	107,593	$ 5	107,588
Equity component of convertible senior notes, net	27,951		27,951
Stock-based compensation	20,960		20,960
Net loss	(41,978)			(41,978)
Balance, end of period (in shares) at Dec. 31, 2018		90,151,341
Balance, end of period at Dec. 31, 2018	$ 371,938	$ 90	542,829	(170,981)	0
Redeemable convertible preferred stock ending balance (in shares) at Dec. 31, 2019	0
Redeemable convertible preferred stock ending balance at Dec. 31, 2019	$ 0
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to employee stock purchase plan (in shares)		490,717
Issuance of common stock pursuant to employee stock purchase program	6,732	$ 0	6,732
Issuance of common stock pursuant to exercise of stock options (in shares)		1,666,162
Issuance of common stock pursuant to exercise of stock options	9,570	$ 2	9,568
Issuance of common stock pursuant to settlement restricted stock units (in shares)		966,037
Issuance of common stock pursuant to restricted stock units	0	$ 1	(1)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(272,660)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(5,126)		(5,126)
Stock-based compensation	29,095		29,095
Other comprehensive income	42				42
Net loss	$ (80,805)			(80,805)
Balance, end of period (in shares) at Dec. 31, 2019	93,001,597	93,001,597
Balance, end of period at Dec. 31, 2019	$ 331,446	$ 93	583,097	(251,786)	42
Increase (Decrease) in Temporary Equity [Roll Forward]
Issuance of convertible preferred stock, net (in shares)	40,000
Issuance of convertible preferred stock, net	$ 39,823
Redeemable convertible preferred stock ending balance (in shares) at Dec. 31, 2020	40,000
Redeemable convertible preferred stock ending balance at Dec. 31, 2020	$ 39,823
Increase (Decrease) in Stockholders' Equity
Issuance of common stock pursuant to employee stock purchase plan (in shares)		320,609
Issuance of common stock pursuant to employee stock purchase program	$ 8,174	$ 0	8,174
Issuance of common stock pursuant to exercise of stock options (in shares)	2,011,938	2,011,938
Issuance of common stock pursuant to exercise of stock options	$ 12,705	$ 2	12,703
Issuance of common stock pursuant to settlement restricted stock units (in shares)		1,490,506
Issuance of common stock pursuant to restricted stock units	0	$ 2	(2)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units (in shares)		(439,131)
Common stock surrendered for employees' tax liability upon settlement of restricted stock units	(16,852)		(16,852)
Issuance of common stock in connection with repurchase of convertible senior notes (in shares)		2,056,180
Issuance of common stock in connection with repurchase of convertible senior notes	(699)	$ 2	(701)
Issuance of common stock as dividend on convertible preferred stock (in shares)		61,280
Issuance of common stock, net (in shares)		4,484,305
Issuance of common stock, net	69,701	$ 4	69,697
Equity component of convertible senior notes, net	165,257		165,257
Stock-based compensation	39,321		39,321
Issuance of common stock in connection with conversion of convertible senior notes (in shares)		13,310
Issuance of common stock in connection with conversion of convertible senior notes	(138)	$ 0	(138)
Other comprehensive income	169				169
Net loss	$ (18,527)			(18,527)
Balance, end of period (in shares) at Dec. 31, 2020	103,000,594	103,000,594
Balance, end of period at Dec. 31, 2020	$ 590,557	$ 103	$ 860,556	$ (270,313)	$ 211