Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) (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, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ (30)	$ 246	$ 563	$ 159
Gain (Loss) on Instruments Designated at Fair Value and Related Derivatives [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	(50)	241	520	115
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	42	(15)	269	(253)
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	5	(2)	18	(57)
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	(67)	234	272	474
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	(12)	42	12	0
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	(1)	(1)	0	0
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	0	(9)	0	(5)
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Mark-to-market on the related derivatives	$ 3	$ (3)	$ (8)	$ 0