Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Public Offering [Member]	ATM Facility [Member]	Common Stock [Member]	Common Stock [Member] Public Offering [Member]	Common Stock [Member] ATM Facility [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Public Offering [Member]	Additional Paid-in Capital [Member] ATM Facility [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2019	$ 186,013			$ 3			$ 330,714			$ (144,704)
Beginning balance, shares at Dec. 31, 2019				31,643,000
Vesting of restricted stock awards and units, shares				31,000
Exercise of stock options	270						270
Exercise of stock options, shares				148,000
Issuance of common stock, net of offering costs		$ 163,849	$ 8,130		$ 1			$ 163,848	$ 8,130
Issuance of common stock upon public offering, net of offering costs, shares					9,350,000	384,000
Issuance of common stock under 2018 employee stock purchase plan	166						166
Issuance of common stock under 2018 employee stock purchase plan, shares				13,000
Stock-based compensation expense	15,628						15,628
Net loss	(119,712)									(119,712)
Ending balance at Dec. 31, 2020	254,344			$ 4			518,756			(264,416)
Ending balance, shares at Dec. 31, 2020				41,569,000
Vesting of restricted stock awards and units, shares				1,000
Exercise of stock options	$ 920						920
Exercise of stock options, shares	226,180			226,000
Issuance of common stock, net of offering costs			$ 14,550						$ 14,550
Issuance of common stock upon public offering, net of offering costs, shares						1,829,000
Issuance of common stock under 2018 employee stock purchase plan	$ 209						209
Issuance of common stock under 2018 employee stock purchase plan, shares				27,000
Stock-based compensation expense	18,579						18,579
Net loss	(119,126)									(119,126)
Ending balance at Dec. 31, 2021	$ 169,476			$ 4			$ 553,014			$ (383,542)
Ending balance, shares at Dec. 31, 2021				43,652,000