Debt (Details 2) (USD $)	0 Months Ended	3 Months Ended	9 Months Ended
	Sep. 19, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Long-term Debt
Gross Carrying Amount		$ 2,250,000,000	$ 2,250,000,000
Unamortized Discount		(39,000,000)	(39,000,000)
Net Carrying Amount		2,211,000,000	2,211,000,000		0
Maturites of Debt
2013 (remaining three months)		0	0
2014		0	0
2015		0	0
2016		0	0
2017		0	0
Thereafter		2,250,000,000	2,250,000,000
Total		2,250,000,000	2,250,000,000
Deferred Financing Costs
Deferred Financing Costs		7,000,000	7,000,000
Proceeds From Issuance of Unsecured Notes	2,211,000,000
Fees paid	39,000,000	39,000,000	39,000,000
Deposit in escrow			(71,000,000)	0
Percentage of principal repayable to option holders upon certain criteria		101.00%	101.00%
Maximum percentage of outstanding Notes that can be redeemed with net cash proceeds from one or more qualified equity offerings		35.00%	35.00%
2021 Notes
Long-term Debt
Gross Carrying Amount	1,500,000,000	1,500,000,000	1,500,000,000
Unamortized Discount		(26,000,000)	(26,000,000)
Net Carrying Amount		1,474,000,000	1,474,000,000
Maturites of Debt
Total	1,500,000,000	1,500,000,000	1,500,000,000
Interest payable		3,000,000	3,000,000
Deferred Financing Costs
Interest rate	5.625%
2021 Notes | Fair value measurements using significant other observable inputs (Level 2)
Deferred Financing Costs
Fair Value of Notes		1,500,000,000	1,500,000,000
2023 Notes
Long-term Debt
Gross Carrying Amount	750,000,000	750,000,000	750,000,000
Unamortized Discount		(13,000,000)	(13,000,000)
Net Carrying Amount		737,000,000	737,000,000
Maturites of Debt
Total	750,000,000	750,000,000	750,000,000
Interest payable		1,000,000	1,000,000
Deferred Financing Costs
Interest rate	6.125%
2023 Notes | Fair value measurements using significant other observable inputs (Level 2)
Deferred Financing Costs
Fair Value of Notes		$ 750,000,000	$ 750,000,000