Derivative Financial Instruments - Impact of Derivatives on Consolidated Statement of Income (Details) - Derivatives not designated as hedging instruments - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	$ 161	$ 176	$ 469	$ 546
Foreign exchange contracts | Trading services
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	161	177	477	546
Interest-rate contracts | Trading services
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	(1)	0	(6)	(1)
Interest-rate contracts | Processing fees and other revenue
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	0	0	1	0
Credit derivative contracts | Trading services
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	0	0	(1)
Other derivative contracts | Trading services
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	1	(1)	(2)	1
Other derivative contracts | Compensation and employee benefits
Derivative [Line Items]
Amount of gain (loss) on derivative recognized in income	$ (41)	$ (28)	$ (168)	$ (121)