CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Trade accounts receivable, allowances	$ 6,023	$ 5,572
Preferred stock, par value (in dollars per share)	$ 0	$ 0
Preferred stock, authorized shares (in shares)	15,000,000	15,000,000
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	60,000,000	60,000,000
Common stock, shares issued (in shares)	46,238,000	45,857,000
Treasury stock, shares (in shares)	8,915,000	8,915,000