Stockholders' Equity (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Common Stock
Balance, beginning	$ 365,093	$ 398,101	$ 419,476	$ 182,282	$ 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	2,306	71	$ 304	2,004		74
Shares issued under stock option and employee stock purchase plans					(25)
Shares issued in underwritten offering, net				269,893
Stock-based compensation	4,496	3,454	3,153	3,029	1,509	1,275
Unrealized gain (loss) on marketable securities	305	(529)	(1,782)	(44)	5	(2)	$ (2,006)	(41)
Net loss	(26,784)	(36,004)	(23,050)	(20,452)	(13,373)	(16,538)	(85,838)	(50,363)
Balance, ending	$ 345,416	365,093	398,101	436,712	182,282	194,166	$ 345,416	436,712
Balance (in shares)	47,096,063						47,096,063
Aggregate gross offering price available	$ 50,000						$ 50,000
Common Stock
Common Stock
Balance, beginning	$ 47	$ 47	$ 47	$ 40	$ 40	$ 40	$ 47	$ 40
Balance (in shares)	46,764,703	46,754,348	46,730,198	39,616,696	39,614,638	39,603,771	46,730,198	39,603,771
Shares issued under stock option and employee stock purchase plans (in shares)	331,360	10,355	24,150	201,406	2,058	10,867
Shares issued in underwritten offering, net				$ 7
Shares issued in underwritten offering, net (in shares)				6,845,238
Balance, ending	$ 47	$ 47	$ 47	$ 47	$ 40	$ 40	$ 47	$ 47
Balance (in shares)	47,096,063	46,764,703	46,754,348	46,663,340	39,616,696	39,614,638	47,096,063	46,663,340
Additional Paid-In Capital
Common Stock
Balance, beginning	$ 1,568,124	$ 1,564,599	$ 1,561,142	$ 1,282,657	$ 1,281,173	$ 1,279,824	$ 1,561,142	$ 1,279,824
Shares issued under stock option and employee stock purchase plans	2,306	71	304	2,004		74
Shares issued under stock option and employee stock purchase plans					(25)
Shares issued in underwritten offering, net				269,886
Stock-based compensation	4,496	3,454	3,153	3,029	1,509	1,275
Balance, ending	1,574,926	1,568,124	1,564,599	1,557,576	1,282,657	1,281,173	1,574,926	1,557,576
Accumulated Other Comprehensive Income.
Common Stock
Balance, beginning	(417)	112	1,894	2,592	2,587	2,589	1,894	2,589
Unrealized gain (loss) on marketable securities	305	(529)	(1,782)	(44)	5	(2)
Balance, ending	(112)	(417)	112	2,548	2,592	2,587	(112)	2,548
Accumulated Deficit
Common Stock
Balance, beginning	(1,202,661)	(1,166,657)	(1,143,607)	(1,103,007)	(1,089,634)	(1,073,096)	(1,143,607)	(1,073,096)
Net loss	(26,784)	(36,004)	(23,050)	(20,452)	(13,373)	(16,538)
Balance, ending	$ (1,229,445)	$ (1,202,661)	$ (1,166,657)	$ (1,123,459)	$ (1,103,007)	$ (1,089,634)	$ (1,229,445)	$ (1,123,459)