Derivative Financial Instruments - Gains and Losses on Derivative Instruments Held For Other Purpose (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	$ 221	$ 292
Other Income [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	(62)	(90)
Other Income [Member] | Foreign exchange contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	(31)	14
Other Income [Member] | Equity contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	315	364
Other Income [Member] | Credit contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	0	(3)
Residential mortgage banking revenue [Member] | Interest rate contracts [Member]
Derivatives, Fair Value [Line Items]
Derivative instruments, gain (loss) recognized in income net	$ (1)	$ 7