CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Receivables, allowance for doubtful accounts	$ 7,114	$ 5,841
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)	89,479,859	89,154,190
Treasury stock, shares (in shares)	9,150,564	7,958,510