Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	$ 171	$ (308)	$ 336	$ 80
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	184	(281)	345	68
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	111	(142)	325	(33)
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	8	6	20	5
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	81	(125)	32	132
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Precious metals contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	0	0	0	1
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	0	(3)	0	(3)
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	0	1	0	1
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Income on Derivatives held for other purposes	$ (29)	$ (45)	$ (41)	$ (23)