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, Common [Member]	Retained Earnings [Member]	Total
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
Stock-based compensation				5,211			5,211
Components of net loss						(9,220)	(9,220)
Employee stock purchase plan				66			66
Employee stock purchase plan, shares			14,569
Stock issued for the exercise of stock options				45			45
Stock issued for the exercise of stock options, shares			40,523
Preferred stock conversion
Preferred stock conversion, shares	(1)		2,025
Share-based compensation, shares			10,699
Ending balance, value at Jun. 30, 2022	$ 5,584	$ 6	$ 75	537,963	(206)	(507,896)	29,942
Ending balance, shares at Jun. 30, 2022	22,386	5,610,121	74,686,056
Beginning balance, value at Mar. 31, 2022	$ 5,584	$ 6	$ 75	535,209	(206)	(502,762)	32,322
Beginning balance, shares at Mar. 31, 2022	22,386	5,610,121	74,647,329
Stock issued for the exercise of stock options				26			26
Stock issued for the exercise of stock options and stock appreciation rights, shares			30,229
Stock-based compensation				2,698			2,698
Components of net loss						(5,134)	(5,134)
Employee stock purchase plan				30			30
Employee stock purchase plan, shares			8,498
Ending balance, value at Jun. 30, 2022	$ 5,584	$ 6	$ 75	537,963	(206)	(507,896)	29,942
Ending balance, shares at Jun. 30, 2022	22,386	5,610,121	74,686,056
Beginning balance, value at Dec. 31, 2022	$ 5,583	$ 6	$ 75	543,438	(206)	(516,967)	26,346
Beginning balance, shares at Dec. 31, 2022	22,383	5,610,121	74,874,459
Stock-based compensation				5,314			5,314
Components of net loss						(10,304)	(10,304)
Employee stock purchase plan				48			48
Employee stock purchase plan, shares			24,568
Stock issued for the exercise of stock options				(18)			$ (18)
Stock issued for the exercise of stock options, shares			29,384				29,188
Preferred stock conversion		$ (6)	$ 6
Preferred stock conversion, shares		(5,610,121)	5,610,121
Share-based compensation, shares			144,054
Ending balance, value at Jun. 30, 2023	$ 5,583		$ 81	548,782	(206)	(527,271)	21,386
Ending balance, shares at Jun. 30, 2023	22,383		80,682,586
Beginning balance, value at Mar. 31, 2023	$ 5,583	$ 6	$ 75	546,149	(206)	(522,314)	23,710
Beginning balance, shares at Mar. 31, 2023	22,383	5,610,121	75,059,499
Stock-based compensation				2,660			2,660
Components of net loss						(4,957)	(4,957)
Employee stock purchase plan				25			25
Employee stock purchase plan, shares			12,770
Stock issued for the exercise of stock options				(52)			(52)
Stock issued for the exercise of stock options, shares			196
Preferred stock conversion		$ (6)	$ 6
Preferred stock conversion, shares		(5,610,121)	5,610,121
Ending balance, value at Jun. 30, 2023	$ 5,583		$ 81	$ 548,782	$ (206)	$ (527,271)	$ 21,386
Ending balance, shares at Jun. 30, 2023	22,383		80,682,586