Statements of Convertible Preferred Stock and Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Convertible Preferred Stock Series A [Member]	Convertible Preferred Stock Series B [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Total
Beginning balance, value at Dec. 31, 2020	$ 5,605	$ 6	$ 74	$ 522,710	$ (206)	$ (487,960)	$ 34,624
Beginning balance, shares at Dec. 31, 2020	22,513	5,610,121	73,694,203
Issuance of common stock				253			253
Issuance of common stock, shares			154,806
Share-based compensation				1,371			1,371
Share-based compensation, shares			30,250
Components of net loss						(1,532)	(1,532)
Employee stock purchase plan				29			29
Employee stock purchase plan, shares			6,003
Preferred stock conversion	$ (27)			26			26
Preferred stock conversion, shares	(105)		204,397
Ending balance, value at Mar. 31, 2021	$ 5,578	$ 6	$ 74	524,389	(206)	(489,492)	34,771
Ending balance, shares at Mar. 31, 2021	22,408	5,610,121	74,089,659
Beginning balance, value at Dec. 31, 2021	$ 5,584	$ 6	$ 75	532,641	(206)	(498,676)	33,840
Beginning balance, shares at Dec. 31, 2021	22,387	5,610,121	74,618,240
Issuance of common stock				18			18
Issuance of common stock, shares			10,294
Share-based compensation				2,514			2,514
Share-based compensation, shares			10,699
Components of net loss						(4,086)	(4,086)
Employee stock purchase plan				36			36
Employee stock purchase plan, shares			6,071
Preferred stock conversion
Preferred stock conversion, shares	(1)		2,025
Ending balance, value at Mar. 31, 2022	$ 5,584	$ 6	$ 75	$ 535,209	$ (206)	$ (502,762)	$ 32,322
Ending balance, shares at Mar. 31, 2022	22,386	5,610,121	74,647,329