Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Trade accounts receivable, allowances (in dollars)	$ 845	$ 964
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, Authorized shares	1,000,000	0
Preferred stock, issued shares	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, Authorized shares	80,000,000	80,000,000
Common stock, issued shares	46,441,428	45,680,042
Treasury stock, shares	16,151	12,420