Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Cumulative Effect of Adoption of ASU 2016-02 [Member]	Private Placement [Member]	Common Stock [Member]	Common Stock [Member] Private Placement [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Private Placement [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member] Cumulative Effect of Adoption of ASU 2016-02 [Member]
Beginning Balances at Dec. 31, 2018	$ 59,945	$ (1,328)		$ 1		$ 510,509		$ (450,565)	$ (1,328)
Beginning Balances, shares at Dec. 31, 2018				11,266,151
Issuance of common stock, net of issuance costs	25,128			$ 1		25,127
Issuance of common stock, net of issuance costs, shares				3,633,334
Issuance of common stock upon exercise of options	$ 95					95
Issuance of common stock upon exercise of options, shares	39,686			39,686
Issuance of common stock under employee benefit plans	$ 28					28
Issuance of common stock under employee benefit plans, shares				62,624
Stock-based compensation	3,399					3,399
Net loss	(18,218)							(18,218)
Ending Balances at Dec. 31, 2019	69,049			$ 2		539,158		(470,111)
Ending Balances, shares at Dec. 31, 2019				15,001,795
Issuance of common stock, net of issuance costs			$ 4,922				$ 4,922
Issuance of common stock, net of issuance costs, shares					931,098
Issuance of common stock upon exercise of options	$ 315					315
Issuance of common stock upon exercise of options, shares	114,515			114,515
Issuance of common stock under employee benefit plans	$ 80					80
Issuance of common stock under employee benefit plans, shares				56,291
Issuance of common stock, net of issuance costs	2,266					2,266
Issuance of common stock, net of issuance costs				377,400
Stock-based compensation	1,966					1,966
Net loss	(30,543)							(30,543)
Ending Balances at Dec. 31, 2020	$ 48,055			$ 2		$ 548,707		$ (500,654)
Ending Balances, shares at Dec. 31, 2020				16,481,099