Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Consolidated Balance Sheets
Receivables, allowance for doubtful accounts	$ 10,885	$ 9,979
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	160,000,000	160,000,000
Common stock, shares issued	95,345,362	95,345,362
Common stock, shares outstanding	58,053,476	58,277,646
Treasury stock, shares	37,291,886	37,067,716