Derivative Instruments And Hedging Activities (Statement Of Gains and Losses on Derivative Instruments Reported in Statement of Comprehensive Income) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	$ (3,466)	$ (4,309)	$ (4,740)
Servicing asset valuation and hedge activities, net	(8)	(789)	(394)
Gain (loss) on mortgage and automotive loans, net	532	470	1,239
Other income, net of losses	747	493	334
Other operating expenses	(3,498)	(2,936)	(3,078)
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	523	17	35
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(85)	57	31
Gain (Loss) on Derivative Instruments, Net, Pretax	409	118	108
Interest Gain For Qualifying Accounting Hedges Of Debt	123	257	322
Gains on amortization of deferred basis adjustments on the hedged items	231	229	164
Gain (Loss) from Revaulation of Foreign-Denominated Debt or Receivable	75	(77)	(53)
Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Recognized in Income, Ineffective Portion and Amount Excluded from Effectiveness Testing, Net	(29)	44	42
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Gain (Loss) Recognized in Earnings on Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	164	892	161
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Gain (Loss) Recognized in Earnings on Hedged Item [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	(193)	(848)	(119)
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	(3)	(3)	0
Servicing asset valuation and hedge activities, net	669	817	478
Gain (loss) on mortgage and automotive loans, net	(125)	(727)	(332)
Other income, net of losses	(18)	(70)	(102)
Other operating expenses	0	0	(9)
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Gain (Loss) Recognized in Earnings on Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other income, net of losses	0	35	0
Foreign Exchange Contract [Member] | Designated as Hedging Instrument [Member] | Gain (Loss) Recognized in Earnings on Hedged Item [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other income, net of losses	0	(35)	0
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	(39)	61	(127)
Other income, net of losses	(48)	17	158
Other operating expenses	$ 2	$ (21)	$ 0