Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,920	$ 2,087
Common stock, par value
Common stock, shares authorized	40,000,000	40,000,000
Common stock, shares issued	24,052,000	23,948,000
Common Stock, shares outstanding	24,052,000	23,948,000