Derivative Financial Instruments (Effect of Derivative Instruments on the Consolidated Statements of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Cash Flow Hedges [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income, Effective Portion, Net	$ (28)	$ (120)	$ (72)	$ (201)
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	13	9	32	23
Cash Flow Hedges [Member] | Interest Rate Contract [Member] | Interest Income [Member]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	(1)	(7)	(9)	(20)
Cash Flow Hedges [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Derivative Instruments, (Gain) Loss Reclassified from Accumulated OCI into Income, Effective Portion, Net	14	16	41	43
Net Investment Hedging [Member] | Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income, Effective Portion, Net	(3)	6	(3)	3
Fair Value Hedges [Member] | Interest Rate Contract [Member]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	66	79	230	205
Fair Value Hedges [Member] | Interest Rate Contract [Member] | Interest Income [Member]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	(6)	(6)	(16)	(16)
Fair Value Hedges [Member] | Interest Rate Contract [Member] | Interest Expense [Member]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	72	85	246	221
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) Recognized in Income, Net	33	315	192	275
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Interest Rate Contract [Member] | Other Income [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	10	6	27	4
Not Designated as Hedging Instrument [Member] | Client-Related and Other Risk Management [Member] | Foreign Exchange Contract [Member] | Other Income [Member]
Gain (Loss) on Foreign Currency Derivative Instruments Not Designated as Hedging Instruments	2	1	6	5
Not Designated as Hedging Instrument [Member] | Mortgage Banking [Member] | Interest Rate Contract [Member] | Mortgage Banking Income [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	(28)	(21)	11	(83)
Not Designated as Hedging Instrument [Member] | Mortgage Servicing Rights [Member] | Interest Rate Contract [Member] | Mortgage Banking Income [Member]
Gain (Loss) on Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 49	$ 329	$ 148	$ 349