CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Shares	Common Shares Open Market Sale Agreement	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2018		37,676,760
Beginning balance at Dec. 31, 2018	$ 279,981	$ 377		$ 575,327	$ 0	$ (295,723)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		12,432,431
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs	431,780	$ 124		431,656
Issuance of common stock under stock option and incentive and employee stock purchase plans (in shares)		1,508,448
Issuance of common stock under stock option and incentive and employee stock purchase plans	6,441	$ 15		6,426
Stock-based compensation expense	20,410			20,410
Other Comprehensive Income (Loss)	111				111
Net loss	(192,256)					(192,256)
Ending balance (in shares) at Dec. 31, 2019		51,617,639
Ending balance at Dec. 31, 2019	546,467	$ 516		1,033,819	111	(487,979)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		3,953,365	294,275
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs	206,276	$ 40	$ 17,900	206,236
Issuance of common stock under stock option and incentive and employee stock purchase plans (in shares)		2,025,140
Issuance of common stock under stock option and incentive and employee stock purchase plans	20,385	$ 20		20,365
Stock-based compensation expense	37,137			37,137
Other Comprehensive Income (Loss)	(100)				(100)
Net loss	(266,489)					(266,489)
Ending balance (in shares) at Dec. 31, 2020		57,596,144
Ending balance at Dec. 31, 2020	543,676	$ 576		1,297,557	11	(754,468)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock sold in public offering, net of underwriting discounts, commissions and offering costs (in shares)		172,094	172,094
Issuance of common stock sold, net of underwriting discounts, commissions, and offering costs	8,549	$ 2	$ 8,500	8,547
Issuance of common stock under stock option and incentive and employee stock purchase plans (in shares)		781,406
Issuance of common stock under stock option and incentive and employee stock purchase plans	6,341	$ 7		6,334
Stock-based compensation expense	46,078			46,078
Other Comprehensive Income (Loss)	40				40
Net loss	(299,964)					(299,964)
Ending balance (in shares) at Dec. 31, 2021		58,549,644
Ending balance at Dec. 31, 2021	$ 304,720	$ 585		$ 1,358,516	$ 51	$ (1,054,432)