CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Trade accounts receivable, allowances	$ 6,319	$ 5,572
Preferred Stock, par value (in dollars per share)
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)	240,000,000	240,000,000
Common stock, shares issued (in shares)	77,666,000	91,714,000
Treasury stock, shares (in shares)	2,946,000	17,830,000