Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Deficit [Member]
Balance at Dec. 31, 2019	$ 17,312	$ 1,334	$ 556,587	$ (540,609)
Balance (in shares) at Dec. 31, 2019		13,380
Stock-based compensation	1,722		1,722
Net loss	(3,028)			(3,028)
Balance at Dec. 31, 2020	16,006	$ 1,334	558,309	(543,637)
Balance (in shares) at Dec. 31, 2020		13,380
Exercise of stock options	$ 239		239
Exercise of stock options (in shares)	30	30
Stock-based compensation	$ 397		397
Net loss	(2,455)			(2,455)
Balance at Dec. 31, 2021	$ 14,187	$ 1,334	$ 558,945	$ (546,092)
Balance (in shares) at Dec. 31, 2021		13,410