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, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	$ 384	$ 17	$ 787	$ 328
Other Income [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	15	494	120	628
Other Income [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	23	23	73	22
Other Income [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	351	(508)	597	(316)
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net		5	(3)	2
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	$ (5)	$ 3		$ (8)