Fair Value Measurements (Details 1) (USD $) In Millions	Jun. 30, 2011	Dec. 31, 2010
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	$ (2,909)	$ (1,954)
Subtotal	(2,051)	1,172
Net derivative liabilities	(1,058)	(363)
Total	(1,058)	(363)
Interest rate swaps [Member] | Quoted prices in active markets (Level 1) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Floor Income Contracts [Member] | Quoted prices in active markets (Level 1) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Cross currency interest rate swaps [Member] | Quoted prices in active markets (Level 1) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Other [Member] | Quoted prices in active markets (Level 1) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	(1)
Quoted prices in active markets (Level 1) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	(1)
Total	0	(1)
Interest rate swaps [Member] | Other Observable Inputs (Level 2) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(135)	(183)
Floor Income Contracts [Member] | Other Observable Inputs (Level 2) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(2,390)	(1,315)
Cross currency interest rate swaps [Member] | Other Observable Inputs (Level 2) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(37)	(43)
Other [Member] | Other Observable Inputs (Level 2) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Other Observable Inputs (Level 2) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(2,562)	(1,541)
Total	(2,562)	(1,541)
Interest rate swaps [Member] | Unobservable Inputs (Level 3) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(199)	(240)
Floor Income Contracts [Member] | Unobservable Inputs (Level 3) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Cross currency interest rate swaps [Member] | Unobservable Inputs (Level 3) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(148)	(172)
Other [Member] | Unobservable Inputs (Level 3) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	0
Unobservable Inputs (Level 3) [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(347)	(412)
Total	(347)	(412)
Interest rate swaps [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(334)	(423)
Floor Income Contracts [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(2,390)	(1,315)
Cross currency interest rate swaps [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	(185)	(215)
Other [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Total derivative instruments	0	(1)
Counterparty Netting [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Net derivative liabilities	858	782
Cash Collateral Pledged [Member]
Valuation of financial instruments that are marked-to-market on a recurring basis
Net derivative liabilities	$ 993	$ 809