Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Common Stock
Balance	$ 398,101	$ 419,476	$ 194,166	$ 209,357	$ 419,476	$ 209,357
Balance (in shares)		46,730,198			46,730,198
Shares issued under stock option and employee stock purchase plans	71	$ 304	25	74
Stock-based compensation	3,454	3,153	1,509	1,275
Unrealized loss on marketable securities	(529)	(1,782)	5	(2)	$ (2,311)	3
Net loss	(36,004)	(23,050)	(13,373)	(16,538)	(59,054)	(29,911)
Balance	$ 365,093	398,101	182,282	194,166	$ 365,093	182,282
Balance (in shares)	46,764,703				46,764,703
Aggregate gross offering price available	$ 50,000				$ 50,000
Common Stock
Common Stock
Balance	$ 47	$ 47	$ 40	$ 40	$ 47	$ 40
Balance (in shares)	46,754,348	46,730,198	39,614,638	39,603,771	46,730,198	39,603,771
Shares issued under stock option and employee stock purchase plans (in shares)	10,355	24,150	2,058	10,867
Balance	$ 47	$ 47	$ 40	$ 40	$ 47	$ 40
Balance (in shares)	46,764,703	46,754,348	39,616,696	39,614,638	46,764,703	39,616,696
Additional Paid-In Capital
Common Stock
Balance	$ 1,564,599	$ 1,561,142	$ 1,281,173	$ 1,279,824	$ 1,561,142	$ 1,279,824
Shares issued under stock option and employee stock purchase plans	71	304	25	74
Stock-based compensation	3,454	3,153	1,509	1,275
Balance	1,568,124	1,564,599	1,282,657	1,281,173	1,568,124	1,282,657
Accumulated Other Comprehensive Income.
Common Stock
Balance	112	1,894	2,587	2,589	1,894	2,589
Unrealized loss on marketable securities	(529)	(1,782)	5	(2)
Balance	(417)	112	2,592	2,587	(417)	2,592
Accumulated Deficit
Common Stock
Balance	(1,166,657)	(1,143,607)	(1,089,634)	(1,073,096)	(1,143,607)	(1,073,096)
Net loss	(36,004)	(23,050)	(13,373)	(16,538)
Balance	$ (1,202,661)	$ (1,166,657)	$ (1,103,007)	$ (1,089,634)	$ (1,202,661)	$ (1,103,007)