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, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 143	$ 171	$ 276	$ 317
Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	41	(256)	115	(266)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(40)	244	(111)	254
Compensation and employee benefits | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(22)	3	(70)	6
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	144	169	278	314
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	18	(159)	60	(155)
Foreign exchange contracts | Processing fees and other revenue | Investment securities | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	(18)	159	(60)	155
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	(1)	2	(1)	3
Interest-rate contracts | Processing fees and other revenue | Contract one | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(24)	(117)	(41)	(132)
Interest-rate contracts | Processing fees and other revenue | Contract two | Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	47	20	96	21
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	22	105	38	121
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	(44)	(20)	(89)	(22)
Other derivative 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	(1)	0
Other derivative contracts | Compensation and employee benefits | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ (22)	$ 3	$ (70)	$ 6