Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Common Stock	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Adjustment	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated Deficit Cumulative Effect, Period of Adoption, Adjustment
Balance at (in shares) at Dec. 31, 2018			30,913,000
Balances at at Dec. 31, 2018	$ 36,869		$ 3	$ 428,162		$ (40)	$ (391,256)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock net of issuance costs (in shares)			3,175,000
Issuance of common stock net of issuance costs	68,273			68,273
Issuance of common stock warrants	3,197		$ 1	3,196
Common stock issued for stock options and restricted stock units	18,387			18,387
Issuance of common stock for employee stock purchase plan (in shares)			203,000
Common stock issued for employee stock purchase plan	1,952			1,952
Tax withholdings related to net share settlements of restricted stock units	(1,474)			(1,474)
Stock-based compensation	17,458			17,458
Net loss	(40,696)						(40,696)
Other comprehensive loss	185					185
Balance at (in shares) at Dec. 31, 2019			36,298,000
Balances at at Dec. 31, 2019	104,151		$ 4	535,954		145	(431,952)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock net of issuance costs (in shares)			5,750,000
Issuance of common stock net of issuance costs	215,765			215,765
Equity component of convertible notes, net	58,543			58,543
Issuance of common stock warrants	737			737
Common stock issued for stock options and restricted stock units	18,751			18,751
Issuance of common stock for employee stock purchase plan (in shares)			89,000
Common stock issued for employee stock purchase plan	2,190			2,190
Exercise of common stock warrant, net (in shares)			414,000
Net exercise of common stock warrants	0
Tax withholdings related to net share settlements of restricted stock units	(2,012)			(2,012)
Stock-based compensation	18,963			18,963
Net loss	(110,078)						(110,078)
Other comprehensive loss	(62)					(62)
Balance at (in shares) at Dec. 31, 2020			44,441,000
Balances at at Dec. 31, 2020	$ 306,948	$ (51,012)	$ 4	848,891	$ (58,543)	83	(542,030)	$ 7,531
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options (in shares)	570,403
Common stock issued for stock options and restricted stock units	$ 6,453		$ 1	6,452
Issuance of common stock for employee stock purchase plan (in shares)			65,000
Common stock issued for employee stock purchase plan	2,428			2,428
Tax withholdings related to net share settlements of restricted stock units	(2,585)			(2,585)
Stock-based compensation	30,385			30,385
Net loss	(115,254)						(115,254)
Other comprehensive loss	(401)					(401)
Balance at (in shares) at Dec. 31, 2021			45,729,000
Balances at at Dec. 31, 2021	$ 176,962		$ 5	$ 827,028		$ (318)	$ (649,753)