CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 8,718	$ 6,961
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)	90,125,838	89,761,305
Treasury stock, shares (in shares)	12,419,025	10,995,361