Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Sep. 30, 2011	Dec. 31, 2010
Consolidated Balance Sheets
Receivables, allowance for doubtful accounts	$ 8,546	$ 9,159
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	59,166,765	59,583,770
Treasury stock, shares	36,178,597	35,761,592