CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Preferred Stock	Additional Paid-In Capital	Accumulated Deficit	Total
Beginning balance (shares) at Dec. 31, 2018	12,960,450	0
Beginning balance, amount at Dec. 31, 2018	$ 13	$ 0	$ 361,218	$ (327,716)	$ 33,515
Share-based compensation			551		$ 551
Issuance of common stock upon exercise of stock options (shares)	156,012				156,012
Issuance of common stock upon exercise of stock options, amount			307		$ 307
Net loss				(5,360)	(5,360)
Ending balance (shares) at Mar. 31, 2019	13,116,462	0
Ending balance, amount at Mar. 31, 2019	$ 13	$ 0	362,076	(333,076)	29,013
Beginning balance (shares) at Dec. 31, 2019	13,146,831	0
Beginning balance, amount at Dec. 31, 2019	$ 13	$ 0	364,028	(342,945)	21,096
Share-based compensation			509		$ 509
Issuance of common stock upon exercise of stock options (shares)					0
Net loss				(4,061)	$ (4,061)
Ending balance (shares) at Mar. 31, 2020	13,146,831	0
Ending balance, amount at Mar. 31, 2020	$ 13	$ 0	$ 364,537	$ (347,006)	$ 17,544