Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Current assets
Allowance for doubtful accounts	$ 400	$ 400
Stockholders' equity
Preferred stock, par value	$ .01	$ .01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ .01	$ .01
Common stock, shares authorized	8,000,000	8,000,000
Common stock, shares issued	5,279,411	5,279,411
Common stock, shares outstanding	5,202,158	5,202,158
Treasury shares	40,920	40,920