CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accounts receivable, allowance for doubtful accounts, current	$ 10	$ 174
Preferred stock, par value (per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares, issued (in shares)	3,672,000	3,663,000
Common stock, shares, outstanding (in shares)	2,685,000	2,936,000
Treasury stock, shares (in shares)	987,000	726,000