Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 809	$ 520
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	75,000,000	75,000,000
Common stock, shares issued	40,312,000	40,312,000
Common stock, shares outstanding	40,086,000	40,086,000