Derivative Financial Instruments (Impact of Derivatives on Consolidated Statement of Income) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 165		$ 148		$ 441		$ 465
Derivatives designated as fair value hedges
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	(66)		0		49		(266)
Amount of Gain (Loss) on Hedged Item Recognized in Consolidated Statement of Income	68		(1)		(43)		253
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	18		4		89		10
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	163		147		441		461
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	(82)		20		(22)		(135)
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	82		(20)		22		135
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		0		0		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		(14)		(17)		(146)
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	(8)		(6)		88		15
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	(23)	[1]	7	[1]	15	[1]	(15)	[1]
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	9		12		(80)		133
Credit 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			1				1
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				(1)
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	18		4		89		10
Other Derivative Contracts [Member] | Trading services | Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of Gain (Loss) on Derivative Recognized in Consolidated Statement of Income	$ 1		$ 0		$ 1		$ 0

[1] Represents amounts reclassified out of other comprehensive income, or OCI. For the three and nine months ended September 30, 2014, $14 million of unrealized gains and $9 million of unrealized losses, respectively, on available-for-sale securities designated in fair value hedges were recognized in OCI. For the three and nine months ended September 30, 2013, $1 million and $61 million, respectively, of unrealized gains on available-for-sale securities designated in fair value hedges were recognized in OCI.