CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accounts receivable, allowances	$ 132	$ 178
Debt instrument debt issuance costs, current	$ 136	$ 59
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	19,581,000	19,450,000
Common stock, shares outstanding	18,161,000	18,055,000
Treasury stock, shares	1,420,000	1,395,000
Series B Convertible Preferred Stock
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, issued	5,000,000	5,000,000
Preferred stock, outstanding	5,000,000	5,000,000