CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Balance sheet (Parenthetical)
Allowance for doubtful accounts	$ 235,747	$ 237,339
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	600,000,000	600,000,000
Common stock, shares, issued	215,075,000	214,607,000
Treasury stock, shares	56,744,000	57,187,000