Statements of Stockholders' Equity - USD ($) $ in Thousands	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2019	48,503	518,233
Balance at Dec. 31, 2019	$ 0	$ 10	$ 355,220	$ (348,335)	$ 6,895
Issuance of common stock in public offerings, net of commissions and issuance costs (in shares)	0	3,707,016
Issuance of common stock in public offerings, net of commissions and issuance costs	$ 0	$ 74	23,572	0	23,646
Employee stock-based compensation	$ 0	$ 0	1,513	0	1,513
Issuance of common stock under officers and directors purchase plan and vesting of restricted stock units (in shares)	0	21,059
Issuance of common stock under officers and directors purchase plan and vesting of restricted stock units	$ 0	$ 1	27	0	28
Issuance of Series A preferred stock to pay dividends (in shares)	3,866	0
Issuance of Series A preferred stock to pay dividends	$ 0	$ 0	3,866	0	3,866
Accretion of Series A preferred stock dividends	0	0	(3,866)	0	(3,866)
Net and comprehensive loss	0	0	0	(19,006)	(19,006)
Net loss	$ 0	$ 0	0	(19,006)	(19,006)
Balance (in shares) at Dec. 31, 2020	52,369	4,246,308
Balance at Dec. 31, 2020	$ 0	$ 85	380,332	(367,341)	13,076
Issuance of common stock in public offerings, net of commissions and issuance costs (in shares)	0	500,000
Issuance of common stock in public offerings, net of commissions and issuance costs	$ 0	$ 10	13,033	0	13,043
Employee stock-based compensation	$ 0	$ 0	1,015	0	1,015
Issuance of Series A preferred stock to pay dividends (in shares)	4,175	0
Issuance of Series A preferred stock to pay dividends	$ 0	$ 0	4,175	0	4,175
Accretion of Series A preferred stock dividends	0	0	(4,175)	0	(4,175)
Net and comprehensive loss	$ 0	$ 0	0	(17,412)	(17,412)
Conversion of Series B preferred stock into common stock (in shares)	(93)	18,600
Issuance of common stock upon vesting of restricted stock units (in shares)	0	13,355
Issuance of common stock upon vesting of restricted stock units	$ 0	$ 1	0	0	1
Net loss	$ 0	$ 0	0	(17,412)	(17,412)
Balance (in shares) at Dec. 31, 2021	56,451	4,778,263
Balance at Dec. 31, 2021	$ 0	$ 96	$ 394,380	$ (384,753)	$ 9,723