Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
CURRENT ASSETS:
Allowance for doubtful accounts	$ 14	$ 14
Accumulated amortization	$ 548	$ 548
STOCKHOLDERS' EQUITY:
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, shares authorized (in shares)	20,000,000	20,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0024	$ 0.0024
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	10,088,297	10,575,182
Common stock, shares outstanding (in shares)	8,663,921	9,150,806
Treasury stock, shares (in shares)	1,424,376	1,424,376