CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 8,268	$ 8,078
Preferred stock, authorized (in shares)	5,000,000	5,000,000
Preferred stock , par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, issued (in shares)	0	0
Common stock, authorized (in shares)	150,000,000	150,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, issued (in shares)	90,171,307	90,200,951
Treasury stock, shares (in shares)	13,512,162	13,760,266