Financial Instruments (Derivatives and hedging) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Notional Amount of Derivatives	$ 329,000
Percentage Of Notional Amount That Is Associated With Reducing Or Eliminating Interest Rate, Currency, Or Market Risk	88.00%
Netting adjustment of derivative gross asset	(3,211)	(3,294)
Netting adjustment of derivative gross liability	(3,188)	(3,281)
Cash collateral assets	(3,731)	(2,310)
Cash collateral liabilities	(616)	(1,027)
Derivative asset, fair value	6,281	10,041
Derivative liability, fair value	1,021	729
Cumulative gain (loss) adjustment for non performance risk	23	13
Excess Collateralization	265	579
Excess Collateral Posted	6
Value Of Securities Pledged That Is Excluded From Cash Collateral	7,442	10,574
Excess Securities Collateral Held	1,116
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	10,940	13,197
Derivative liabilities	2,827	3,385
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,283	2,448
Derivative liabilities	1,998	1,652
Derivatives Associated With Interest Rate, Currency Or Market Risk Reduction Or Elimination [Member]
Derivatives, Fair Value [Line Items]
Notional Amount of Derivatives	290,000
Interest Rate Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	8,824	9,446
Derivative liabilities	995	1,049
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	323	319
Derivative liabilities	188	241
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,115	3,750
Derivative liabilities	1,826	2,325
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,518	1,748
Derivative liabilities	1,714	1,274
Other Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1	1
Derivative liabilities	6	11
Other Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	442	381
Derivative liabilities	$ 96	$ 137