CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 13	$ 9
Stockholders' equity:
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	19,438,178	19,211,826
Common stock, shares outstanding	18,955,264	18,728,192
Treasury stock	482,914	482,914