Derivative Financial Instruments - Impact of Derivatives on Consolidated Statement of Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	$ 691	$ 611	$ 589
Compensation and employee benefits \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	149	106	14
Foreign exchange contracts \| Trading services \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	686	612	586
Interest-rate contracts \| Trading services \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(2)	1	2
Credit derivative contracts \| Trading services \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(1)	1	0
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 income	0	(1)	1
Other derivative contracts \| Trading services \| Derivatives not designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	8	(2)	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 income	149	106	14
Fair Value Hedges \| Derivatives designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(265)	14	(343)
Gain (loss) on fair value hedges recognized in earnings	271	(7)	328
Fair Value Hedges \| Investment securities available for sale \| Foreign exchange contracts \| Processing fees and other revenue \| Derivatives designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(101)	(92)	(183)
Gain (loss) on fair value hedges recognized in earnings	101	92	183
Fair Value Hedges \| Investment securities available for sale \| Interest-rate contracts \| Processing fees and other revenue \| Derivatives designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	16	(44)	32
Gain (loss) on fair value hedges recognized in earnings	(17)	39	(30)
Fair Value Hedges \| Deposits \| Foreign exchange contracts \| Processing fees and other revenue \| Derivatives designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(241)	0	0
Gain (loss) on fair value hedges recognized in earnings	241	0	0
Fair Value Hedges \| Long-term debt \| Interest-rate contracts \| Processing fees and other revenue \| Derivatives designated as hedging instruments
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	61	150	(192)
Gain (loss) on fair value hedges recognized in earnings	$ (54)	$ (138)	$ 175

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624171-113959

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