Derivative Instruments and Other Financial Instruments Used For Hedging - Gain or (Loss) Recognized in Income on Derivative Instruments (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
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	$ 21	$ 26	$ 68	$ 79
Trading Account Activities [Member] | Interest rate derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	17	12	39	31
Trading Account Activities [Member] | Equity derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	3	8	11	21
Trading Account Activities [Member] | Foreign exchange derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	4	7	17	20
Trading Account Activities [Member] | Commodity derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	(1)		3	2
Trading Account Activities [Member] | Other Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	$ (2)	$ (1)	$ (2)	$ 5