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, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Interest and Fee Income, Loans and Leases	$ (4,457)	$ (4,529)	$ (4,539)
Interest on long-term debt	(2,067)	(2,602)	(3,336)
Servicing asset valuation and hedge activities, net	0	(213)	(4)
Gain (loss) on mortgage and automotive loans, net	7	55	379
Other income, net of losses	280	383	737
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(37)	(135)	533
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	(160)	118	(87)
Gain (Loss) on Equity Forward Contract Not Designated as Hedging Instruments	(5)	0	0
Gain (Loss) on Derivative Instruments, Net, Pretax	(139)	5	417
Interest Gain For Qualifying Accounting Hedges Of Debt	112	131	119
Gains on amortization of deferred basis adjustments on the hedged items	155	247	226
Gain (Loss) from Revaulation of Foreign-Denominated Debt or Receivable	165	(117)	87
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	63	22	(29)
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Gain (Loss) Recognized in Earnings on Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest and Fee Income, Loans and Leases	(15)	(7)	0
Interest on long-term debt	199	(389)	164
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 and Fee Income, Loans and Leases	(34)	(2)	0
Interest on long-term debt	(185)	402	(193)
Interest Rate Contract [Member] | Designated as Hedging Instrument [Member] | Gain (loss) Excluded from Earnings on Derivatives [Domain]
Derivative Instruments, Gain (Loss) [Line Items]
Interest and Fee Income, Loans and Leases	61	9
Interest Rate Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Servicing asset valuation and hedge activities, net	0	(112)	556
Gain (loss) on mortgage and automotive loans, net	0	(37)	(5)
Other income, net of losses	(37)	14	(18)
Foreign Exchange Contract [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest on long-term debt	(172)	94	(39)
Other income, net of losses	12	24	(48)
Forward Contracts [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other income, net of losses	$ (5)	$ 0	$ 0