Financial Instruments (Derivatives and hedging) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	$ 302,000
Derivative asset, fair value	659	506
Derivative liability, fair value	499	988
Cumulative gain (loss) adjustment for non performance risk	29	(7)
Excess Collateralization	177	160
Excess Collateral Posted	56	37
Excess Securities Collateral Held	41	286
Netting Adjustment Including Collateral [Member] | Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	(6,106)	(6,546)
Derivative liabilities	(3,716)	(4,162)
Recognized In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	8,284	8,890
Derivative liabilities	4,215	5,150
Netting Adjustment [Member] | Amounts Offset In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	(3,378)	(3,927)
Derivative liabilities	(3,407)	(3,920)
Cash Collateral [Member] | Amounts Offset In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	(2,728)	(2,619)
Derivative liabilities	(309)	(242)
Securities Pledged as Collateral [Member] | Not Offset In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	(1,519)	(1,838)
Derivative liabilities	0	0
Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	5,451	5,583
Derivative liabilities	2,485	2,947
Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,650	2,080
Derivative liabilities	1,689	1,962
Derivatives Associated With Interest Rate, Currency Or Market Risk Reduction Or Elimination [Member]
Derivatives, Fair Value [Line Items]
Derivative, Notional Amount	293,000
Percentage Of Notional Amount That Is Associated With Reducing Or Eliminating Interest Rate, Currency, Or Market Risk	97.01987%
Gross Derivatives [Member] | Recognized In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	7,101	7,663
Derivative liabilities	4,174	4,909
Gross Accrued Interest [Member] | Recognized In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,183	1,227
Derivative liabilities	41	241
Net Derivative [Member] | Recognized In Statement Of Financial Position [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	2,178	2,344
Derivative liabilities	499	988
Interest Rate Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	4,187	3,837
Derivative liabilities	1,350	1,989
Interest Rate Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	288	270
Derivative liabilities	151	175
Foreign Exchange Contract [Member] | Derivatives Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,264	1,746
Derivative liabilities	1,135	958
Foreign Exchange Contract [Member] | Derivatives Not Accounted For As Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative assets	1,318	1,753
Derivative liabilities	1,516	1,765
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	44	57
Derivative liabilities	$ 22	$ 22