CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 33	$ 29
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	62,877,530	60,621,338
Common stock, shares outstanding	62,877,530	60,621,338