Condensed 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	484		484
Net income (loss)	249			249
Balance at Mar. 31, 2020	18,045	$ 1,334	557,071	(540,360)
Balance (in shares) at Mar. 31, 2020		13,380
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
Stock-based compensation	208		208
Net income (loss)	(696)			(696)
Balance at Mar. 31, 2021	$ 15,757	$ 1,334	$ 558,756	$ (544,333)
Balance (in shares) at Mar. 31, 2021		13,410