Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets
Allowance for doubtful accounts	$ 117,397	$ 111,707
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	1,000,000,000	1,000,000,000
Common stock, shares issued	761,067,000	729,516,000
Common stock, shares outstanding	687,730,000	656,360,000