CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 30	$ 33
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares issued (in shares)	63,771,860	62,877,530
Common stock, shares outstanding (in shares)	63,771,860	62,877,530