CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Trade accounts receivable, allowances	$ 3,719	$ 8,882
Preferred Stock, par value (in dollars per share)	$ 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)	240,000,000	240,000,000
Common stock, shares issued (in shares)	88,044,000	81,306,000
Treasury stock, shares (in shares)	2,881,000	2,912,000