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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	$ 19	$ 21	$ 24	$ 47
Trading Derivatives [Member] | Interest rate derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	10	7	9	21
Trading Derivatives [Member] | Equity Derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	3	4	6	9
Trading Derivatives [Member] | Foreign exchange derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	5	6	8	13
Trading Derivatives [Member] | Commodity derivative contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments	1	4		4
Trading Derivatives [Member] | Other contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain or (Loss) Recognized in Income on Derivative Instruments			$ 1