Financial Instruments (Derivatives and hedging) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 330,000
Netting adjustment of derivative gross asset	(3,444)	(3,294)
Netting adjustment of derivative gross liability	(3,423)	(3,281)
Cash collateral assets	(3,939)	(2,310)
Cash collateral liabilities	(710)	(1,027)
Derivative asset, fair value	5,334	10,041
Derivative liability, fair value	863	729
Cumulative gain (loss) adjustment for non performance risk	(21)	(13)
Excess Collateralization	69	579
Excess Collateral Posted	13
Value Of Securities Pledged That Is Excluded From Cash Collateral	6,241	10,574
Excess Securities Collateral Held	347
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	9,805	13,197
Derivative liabilities	3,973	3,385
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,912	2,448
Derivative liabilities	1,023	1,652
Derivatives Associated With Interest Rate, Currency Or Market Risk Reduction Or Elimination [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	287,000
Percentage Of Notional Amount That Is Associated With Reducing Or Eliminating Interest Rate, Currency, Or Market Risk	87.00%
Interest Rate Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	8,967	9,446
Derivative liabilities	768	1,049
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	364	319
Derivative liabilities	195	241
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	836	3,750
Derivative liabilities	3,204	2,325
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,140	1,748
Derivative liabilities	761	1,274
Other Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2	1
Derivative liabilities	1	11
Other Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	408	381
Derivative liabilities	$ 67	$ 137