CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Trade accounts receivable, allowance	$ 4,394	$ 3,719
Preferred stock, authorized shares (in shares)	15,000,000	15,000,000
Preferred stock, outstanding shares (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, authorized shares (in shares)	240,000,000	240,000,000
Common stock, issued shares (in shares)	88,351,000	88,044,000
Treasury stock, shares (in shares)	2,869,000	2,881,000