Condensed Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Series A Convertible Preferred Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2020	$ 23,692	$ 1		$ 287,218	$ (263,527)
Beginning balance, shares at Dec. 31, 2020		13,397,041	2,111
Stock-based compensation expense	460			460
Shares issued upon exercise of common stock warrants	19			19
Shares issued upon exercise of common stock warrants, shares		5,304
Shares issued upon conversion of preferred stock, shares		23
Shares issued upon exercise of options	1			1
Shares issued upon exercise of options, shares		194
Net income (loss)	2,599				2,599
Ending balance at Mar. 31, 2021	26,771	$ 1		287,698	(260,928)
Ending balance, shares at Mar. 31, 2021		13,402,562	2,111
Beginning balance at Dec. 31, 2020	23,692	$ 1		287,218	(263,527)
Beginning balance, shares at Dec. 31, 2020		13,397,041	2,111
Net income (loss)	(2,800)
Ending balance at Dec. 31, 2021	37,480	$ 2		303,829	(266,351)
Ending balance, shares at Dec. 31, 2021		16,849,805	2,106
Stock-based compensation expense	2,317			2,317
Shares issued upon conversion of preferred stock, shares		356	(16)
Net income (loss)	(2,768)				(2,768)
Ending balance at Mar. 31, 2022	$ 37,029	$ 2		$ 306,146	$ (269,119)
Ending balance, shares at Mar. 31, 2022		16,850,161	2,090