Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Condensed Consolidated Balance Sheets [Abstract]
Allowance for doubtful accounts, accounts receivable (in dollars)	$ 26,118	$ 28,323
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	33,323,963	32,281,847