Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock Series A Convertible Preferred Stock	Preferred Stock Series A and B Convertible Preferred Stock	Preferred Stock	Common stock At-the-market sales	Common stock Series A Convertible Preferred Stock	Common stock	Additional Paid in Capital. At-the-market sales	Additional Paid in Capital. Series A Convertible Preferred Stock	Additional Paid in Capital.	Accumulated Other Comprehensive Income	Accumulated Deficit	At-the-market sales	Series A and B Convertible Preferred Stock	Total
Balance at Dec. 31, 2020									$ 361,548	$ 3	$ (312,223)			$ 49,328
Balance (in shares) at Dec. 31, 2020						2,189,094
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs									742					742
Issuance of common stock							$ 960					$ 960
Issuance of common stock (in shares)				13,023
Issuance of common stock upon exercise of options									75					75
Issuance of common stock upon exercise of options (in shares)						3,160
Vesting of RSUs (in shares)						1,316
Warrants issued in connection with long-term debt									1,080					1,080
Unrealized net gain on marketable securities										$ (3)				(3)
Net loss											(17,128)			(17,128)
Balance at Mar. 31, 2021									364,405		(329,351)			35,054
Balance (in shares) at Mar. 31, 2021						2,206,593
Balance at Dec. 31, 2021									396,388		(387,117)			9,271
Balance (in shares) at Dec. 31, 2021						3,034,901
Increase (decrease) in stockholders' equity
Share-based compensation - stock options and RSUs									764					764
Issuance of common stock							$ 348					$ 348
Issuance of common stock (in shares)				25,623
Registered direct financing costs, inclusive of warrants			$ (965)						244					(721)
Conversion of convertible preferred stock	$ (897)	$ 4,850						$ 897					$ 4,850
Conversion of convertible preferred stock (in shares)	(2,425)	4,850			303,125
Vesting of RSUs (in shares)						1,773
Warrants issued in connection with registered direct offering			(2,101)						2,101
Net loss											(11,769)			(11,769)
Balance at Mar. 31, 2022			$ 887						$ 400,742		$ (398,886)			$ 2,743
Balance (in shares) at Mar. 31, 2022			2,425			3,365,422