Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	At The Market Facility Member	Common Stock [Member]	Common Stock [Member] At The Market Facility Member	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] At The Market Facility Member	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 254,344		$ 4		$ 518,756		$ (264,416)
Beginning balance, shares at Dec. 31, 2020			41,569,000
Stock-based compensation expense	9,326				9,326
Exercise of stock options, shares			197,000
Exercise of stock options	850				850
Issuance of common stock under ATM facility, net of offering costs of $67, shares				1,829,000
Issuance of common stock under ATM facility, net of offering costs of $67		$ 14,550				$ 14,550
Issuance of common stock under 2018 employee stock purchase plan	208				208
Issuance of common stock under 2018 employee stock purchase plan, shares			28,000
Net loss	(58,286)						(58,286)
Ending balance at Jun. 30, 2021	220,992		$ 4		543,690		(322,702)
Ending balance, shares at Jun. 30, 2021			43,623,000
Beginning balance at Mar. 31, 2021	232,930		$ 4		524,241		(291,315)
Beginning balance, shares at Mar. 31, 2021			41,766,000
Stock-based compensation expense	4,691				4,691
Issuance of common stock under ATM facility, net of offering costs of $67, shares				1,829,000
Issuance of common stock under ATM facility, net of offering costs of $67		$ 14,550				$ 14,550
Issuance of common stock under 2018 employee stock purchase plan	208				208
Issuance of common stock under 2018 employee stock purchase plan, shares			28,000
Net loss	(31,387)						(31,387)
Ending balance at Jun. 30, 2021	220,992		$ 4		543,690		(322,702)
Ending balance, shares at Jun. 30, 2021			43,623,000
Beginning balance at Dec. 31, 2021	169,476		$ 4		553,014		(383,542)
Beginning balance, shares at Dec. 31, 2021			43,652,000
Stock-based compensation expense	$ 6,611				6,611
Exercise of stock options, shares	0
Issuance of common stock under 2018 employee stock purchase plan	$ 143				143
Issuance of common stock under 2018 employee stock purchase plan, shares			44,000
Net loss	(57,887)						(57,887)
Ending balance at Jun. 30, 2022	118,343		$ 4		559,768		(441,429)
Ending balance, shares at Jun. 30, 2022			43,696,000
Beginning balance at Mar. 31, 2022	143,163		$ 4		556,534		(413,375)
Beginning balance, shares at Mar. 31, 2022			43,696,000
Stock-based compensation expense	3,234				3,234
Net loss	(28,054)						(28,054)
Ending balance at Jun. 30, 2022	$ 118,343		$ 4		$ 559,768		$ (441,429)
Ending balance, shares at Jun. 30, 2022			43,696,000