Statements of Stockholders' Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2018	$ 2	$ 158,912	$ (133,993)	$ 24,921
Balance (in shares) at Dec. 31, 2018	17,095,456
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans		282		282
Issuance of common stock under stock incentive plans (in shares)	97,310
Issuance of common stock in at-the-market offering, net of issuance costs		4,734		4,734
Issuance of common stock (in shares)	888,987
Modification of warrant in conjunction with 2019 Credit Facility		(19)		(19)
Stock-based compensation expense		3,240		3,240
Net loss			(14,669)	(14,669)
Balance at Dec. 31, 2019	$ 2	167,149	(148,662)	18,489
Balance (in shares) at Dec. 31, 2019	18,081,753
Increase (Decrease) in Stockholders' Equity
Issuance of common stock under stock incentive plans		1,595		1,595
Issuance of common stock under stock incentive plans (in shares)	481,376
Issuance of common stock in at-the-market offering, net of issuance costs		2,084		2,084
Issuance of common stock (in shares)	468,427
Stock-based compensation expense		3,604		3,604
Issuance of warrant		152		152
Net loss			(8,512)	(8,512)
Balance at Dec. 31, 2020	$ 2	$ 174,584	$ (157,174)	$ 17,412
Balance (in shares) at Dec. 31, 2020	19,031,556