Derivative Financial Instruments (Impact of Derivatives on Consolidated Statement of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 171	$ 128	$ 317	$ 257
Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(256)	(1)	(266)	38
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	244	5	254	(39)
Foreign exchange contracts | Trading services | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	169	129	314	346
Foreign exchange contracts | Processing fees and other revenue | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	(1)	0	(3)
Foreign exchange contracts | Processing fees and other revenue | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(159)	(26)	(155)	4
Foreign exchange contracts | Processing fees and other revenue | Investment securities [Member] | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	159	26	155	(4)
Interest-rate contracts | Trading services | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	2	0	3	(88)
Interest-rate contracts | Processing fees and other revenue | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	0	0	0	2
Interest-rate contracts | Processing fees and other revenue | Contract one [Member] | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(117)	(31)	(132)	(6)
Interest-rate contracts | Processing fees and other revenue | Contract two [Member] | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	20	56	21	40
Interest-rate contracts | Processing fees and other revenue | Long-term debt | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	105	29	121	2
Interest-rate contracts | Processing fees and other revenue | Investment securities available for sale | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	$ (20)	$ (50)	$ (22)	$ (37)