Financial Instruments (Derivatives and hedging) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 292,000
Netting adjustment of derivative gross asset	(2,532)	(3,009)
Netting adjustment of derivative gross liability	(2,517)	(2,998)
Cash collateral assets	(5,125)	(2,310)
Cash collateral liabilities	(391)	(1,027)
Derivative asset, fair value	3,557	9,671
Derivative liability, fair value	152	498
Excess Collateralization	42	579
Securities Held as Collateral, at Fair Value	10,185
Excess Collateral Posted	10
Excess Securities Collateral Held	359
Securities Held By Third Parties [Member]
Derivatives, Fair Value [Line Items]
Securities Held as Collateral, at Fair Value	5,060
Value Of Securities Pledged That Is Excluded From Cash Collateral	5,419	10,346
Cash [Member]
Derivatives, Fair Value [Line Items]
Securities Held as Collateral, at Fair Value	5,125
Derivatives [Member]
Derivatives, Fair Value [Line Items]
Cumulative gain (loss) adjustment for non performance risk	(15)	(11)
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	9,270	13,165
Derivative liabilities	2,481	3,288
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,944	1,825
Derivative liabilities	579	1,235
Derivatives Associated With Interest Rate, Currency Or Market Risk Reduction Or Elimination [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	282,000
Percentage Of Notional Amount That Is Associated With Reducing Or Eliminating Interest Rate, Currency, Or Market Risk	96.00%
Interest Rate Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	8,443	9,445
Derivative liabilities	719	1,049
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	452	314
Derivative liabilities	195	241
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	827	3,720
Derivative liabilities	1,762	2,239
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,457	1,440
Derivative liabilities	358	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	35	71
Derivative liabilities	$ 26	$ 22