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	$ 296,000
Percentage Of Notional Amount That Is Associated With Reducing Or Eliminating Interest Rate, Currency, Or Market Risk	98.00%
Netting adjustment of derivative gross asset	(2,922)	(3,009)
Netting adjustment of derivative gross liability	(2,900)	(2,998)
Cash collateral assets	(3,731)	(2,310)
Cash collateral liabilities	(616)	(1,027)
Derivative asset, fair value	5,760	9,671
Derivative liability, fair value	715	498
Cumulative gain (loss) adjustment for non performance risk	22	11
Excess Collateralization	265	579
Excess Collateral Posted	6
Value Of Securities Pledged That Is Excluded From Cash Collateral	7,178	10,346
Excess Securities Collateral Held	1,060
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	10,919	13,165
Derivative liabilities	2,712	3,288
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,494	1,825
Derivative liabilities	1,519	1,235
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	9,445
Derivative liabilities	995	1,049
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	319	314
Derivative liabilities	188	241
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,095	3,720
Derivative liabilities	1,717	2,239
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,112	1,440
Derivative liabilities	1,315	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	63	71
Derivative liabilities	$ 16	$ 22