CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Receivables, allowance for doubtful accounts	$ 6,269	$ 5,596
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)	89,050,455	87,732,405
Treasury stock, shares (in shares)	7,551,016	5,005,518