CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data	Sep. 30, 2011	Dec. 31, 2010
Balance sheet (Parenthetical)
Allowance for doubtful accounts	$ 242,444	$ 228,917
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600,000	600,000
Common stock, shares, issued	214,604	214,173
Treasury stock, shares	57,183	43,456