Derivative Financial Instruments (Schedule of Outstanding Hedges: (Notional Amount)) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 4,970	$ 3,153
Swap agreements and forwards | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	1,355	1,578
Options and caps purchased | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	46	68
Options and caps written | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	46	68
Futures | Interest-rate contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	2,434	1,910
Futures | Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	3	0
Forward, swap and spot | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	1,182,949	897,354
Options purchased | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	3,785	9,454
Options written | Foreign exchange contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	3,418	8,734
Credit swap agreements | Credit derivative contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	105	27
Stable value contracts | Other contracts | Derivatives not designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	28,440	33,512
Swap agreements | Interest-rate contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	4,970	3,153
Forward and swap | Foreign exchange contracts | Derivatives designated as hedging instruments
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount of derivatives	$ 3,002	$ 3,477