Debt - Term Loans Narrative (Details) (USD $)	9 Months Ended		3 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2012 Unsecured Debt [Member]	Sep. 30, 2014 Unsecured Debt [Member]	Nov. 07, 2012 Unsecured Debt [Member]	Sep. 30, 2014 Unsecured Debt [Member] Premium on Extinguishment of Term Loan Debt [Member]	Sep. 30, 2014 Unsecured Debt [Member] Unamortized Discount on Extinguishment of Term Loan Debt [Member]	Sep. 30, 2014 Unsecured Debt [Member] Unamortized Deferred Charges on Extinguishment of Term Loan Debt [Member]	Sep. 30, 2014 Senior Notes [Member]	Apr. 24, 2014 Senior Notes [Member]
Long-Term Debt Instrument [Line Items]
Credit Facility Commitment Period			five-year
Unsecured Debt					$ 2,000,000,000
Proceeds from Issuance of Unsecured Debt			1,935,000,000
Long-term Debt, Gross	1,500,000,000								3,000,000,000	3,000,000,000
Gains (Losses) on Extinguishment of Debt	$ (61,000,000)	$ (37,000,000)		$ 90,000,000		$ 40,000,000	$ 30,000,000	$ 20,000,000