CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Receivables,allowance for doubtful accounts	$ 5,758	$ 5,596
Preferred stock , Authorized shares	5,000,000	5,000,000
Preferred stock , par value	$ 0.01	$ 0.01
Preferred stock , Issued
Common stock, Authorized shares	150,000,000	150,000,000
Common stock, par value	$ 0.01	$ 0.01
Common stock, Issued shares	88,360,659	87,732,405
Treasury stock, shares	5,713,071	5,005,518