Balance Sheet (Parenthetical) (USD $) In Millions, except Share data	Jun. 30, 2011	Dec. 31, 2010
Balance Sheet [Abstract]
Accounts receivable, less allowance for doubtful accounts	$ 18	$ 17
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	250,000,000	250,000,000
Preferred stock, non-redeemable shares issued (in shares)	0	0
Preferred stock, non-redeemable shares outstanding (in shares)	0	0
Treasury stock (in shares)	4,676,475	176,475
Common Class A [Member]
Balance Sheet [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	900,000,000	900,000,000
Common stock, shares issued (in shares)	114,699,547	112,494,166
Common Class B [Member]
Balance Sheet [Abstract]
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	25,000,000	25,000,000
Common stock, shares issued (in shares)	0	0
Common stock, shares outstanding (in shares)	2,241,299	2,241,299