Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ (297)	$ (30)	$ (217)	$ 563
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(405)	(50)	(337)	520
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	164	42	131	269
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(18)	5	(13)	18
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(533)	(67)	(401)	272
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Precious metals contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(1)	(12)	0	12
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	0	(1)	(3)	0
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(1)	0	0	0
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ 92	$ 3	$ 69	$ (8)