Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Balances at Dec. 31, 2019	$ 33,150	$ 1	$ 150,280	$ 26	$ (117,157)
Balance (in shares) at Dec. 31, 2019		551
Common stock issued, net	11,625	$ 5	11,620
Common stock issued (in shares)		2,551
Warrants issued, net	7,492		7,492
Exercise of warrants	827	$ 1	826
Exercise of warrants (in shares)		74
Common stock issued pursuant to the vesting of restricted stock units and purchases under employee stock purchase plan	42		42
Common stock issued pursuant to the vesting of restricted stock units and purchases under employee stock purchase plan (in shares)		13
Stock-based compensation	4,082		4,082
Other comprehensive income (loss)	(26)			$ (26)
Net loss	(36,045)				(36,045)
Balances at Dec. 31, 2020	21,147	$ 7	174,342		(153,202)
Balance (in shares) at Dec. 31, 2020		3,189
Common stock issued, net	15,153	$ 1	15,152
Common stock issued (in shares)		3,901
Warrants issued, net	132		132
Restricted stock awards cancelled (shares)		(113)
Common stock issued pursuant to the vesting of restricted stock units and purchases under employee stock purchase plan	74		74
Common stock issued pursuant to the vesting of restricted stock units and purchases under employee stock purchase plan (in shares)		33
Stock-based compensation	2,237		2,237
Net loss	(25,070)				(25,070)
Balances at Dec. 31, 2021	$ 13,673	$ 8	$ 191,937		$ (178,272)
Balance (in shares) at Dec. 31, 2021		7,010