Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data	Jun. 30, 2011	Dec. 31, 2010
Condensed Consolidated Balance Sheets
Accounts receivable, allowance for doubtful accounts	$ 26	$ 29
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	62,607,743	60,621,338
Common stock, shares outstanding	62,607,743	60,621,338