Statements of Stockholders' Equity - USD ($) $ in Thousands	At-the-Market Sales Agreement	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			13		13
Issuance of common stock under stock incentive plans (in shares)		12,607
Stock-based compensation expense			704		704
Net loss				(4,256)	(4,256)
Balance at Mar. 31, 2019		$ 2	159,629	(138,249)	21,382
Balance (in shares) at Mar. 31, 2019		17,108,063
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 in at-the-market offering, net of issuance costs			2,084		2,084
Issuance of common stock (in shares)	468,427	468,427
Issuance of common stock under stock incentive plans			315		315
Issuance of common stock under stock incentive plans (in shares)		88,375
Stock-based compensation expense			805		805
Net loss				(1,732)	(1,732)
Balance at Mar. 31, 2020		$ 2	$ 170,353	$ (150,394)	$ 19,961
Balance (in shares) at Mar. 31, 2020		18,638,555