CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income [Member]
Balance at Dec. 31, 2019	$ 8,330	$ 11	$ 472,765	$ (465,286)	$ 840
Balance, shares at Dec. 31, 2019		10,941,659
Net loss	(13,174)			(13,174)
Issuance of stock, net of issue costs	19,990	$ 15	19,975
Issuance of stock, net of issue costs, shares		1,500,000
Employee stock purchase plan	187	$ 1	186
Employee stock purchase plan, shares		16,166
Vesting of stock units	(19)		(19)
Vesting of stock units, shares		16,285
Stock-based compensation	1,160		1,160
Balance at Mar. 31, 2020	16,474	$ 27	494,067	(478,460)	840
Balance, shares at Mar. 31, 2020		12,474,110
Balance at Dec. 31, 2020	$ 18,541	$ 18	528,362	(510,680)	841
Balance, shares at Dec. 31, 2020	18,139,981	18,139,981
Net loss	$ (12,280)			(12,280)
Issuance of stock, net of issue costs	108,403	$ 11	108,392
Issuance of stock, net of issue costs, shares		10,513,538
Employee stock purchase plan	173		173
Employee stock purchase plan, shares		27,713
Exercise of stock options	10		10
Exercise of stock options, shares		827
Vesting of stock units	(128)		(128)
Vesting of stock units, shares		59,416
Stock-based compensation	988		988
Balance at Mar. 31, 2021	$ 115,707	$ 29	$ 637,797	$ (522,960)	$ 841
Balance, shares at Mar. 31, 2021	28,741,475	28,741,475