Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Allowance for doubtful accounts, accounts receivable (in dollars)	$ 27,687	$ 29,079
Common stock, par value (in dollars per share)	$ 0.1	$ 0.1
Common stock, authorized shares	100,000,000	100,000,000
Common stock, issued shares	74,435,628	74,435,628
Treasury stock, shares	29,659,783	28,247,906