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	$ 293,000
Netting adjustment of derivative gross asset	(3,194)	(3,009)
Netting adjustment of derivative gross liability	(3,173)	(2,998)
Cash collateral assets	(3,939)	(2,310)
Cash collateral liabilities	(710)	(1,027)
Derivative asset, fair value	4,898	9,671
Derivative liability, fair value	622	498
Cumulative gain (loss) adjustment for non performance risk	21	11
Excess Collateralization	69	579
Excess Collateral Posted	13
Value Of Securities Pledged That Is Excluded From Cash Collateral	5,953	10,346
Excess Securities Collateral Held	327
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	9,772	13,165
Derivative liabilities	3,837	3,288
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,259	1,825
Derivative liabilities	668	1,235
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	98.00%
Interest Rate Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	8,967	9,445
Derivative liabilities	768	1,049
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	364	314
Derivative liabilities	195	241
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	805	3,720
Derivative liabilities	3,069	2,239
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,830	1,440
Derivative liabilities	454	972
Other Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Other Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	65	71
Derivative liabilities	$ 19	$ 22