Financial Derivatives (Derivatives Designated in GAAP Hedge Relationships - Fair Value Hedges) (Details) (Fair Value Hedging [Member], Designated as Hedging Instrument [Member], Interest Rate Contracts [Member], USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivatives	$ (357)	$ 121	$ (466)	$ 51
Gain (Loss) on Related Hedged Items Recognized in Income	348	(126)	453	(76)
US Treasury and Government Agencies Securities [Member] | Investment Securities Interest Income [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivatives	41	(48)	63	(29)
Gain (Loss) on Related Hedged Items Recognized in Income	(43)	50	(66)	26
Other Debt Securities [Member] | Investment Securities Interest Income [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivatives	3	(2)	5	(2)
Gain (Loss) on Related Hedged Items Recognized in Income	(3)	2	(5)	2
Subordinated Debts [Member] | Borrowed Funds Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(195)	44	(263)	8
Gain (Loss) on Related Hedged Items Recognized in Income	190	(50)	256	(24)
Bank Notes And Senior Debt [Member] | Borrowed Funds Interest Expense [Member]
Derivatives, Fair Value [Line Items]
Gain (Loss) Recognized in Income on Derivatives	(206)	127	(271)	74
Gain (Loss) on Related Hedged Items Recognized in Income	$ 204	$ (128)	$ 268	$ (80)