Derivative Financial Instruments - Fair Value Hedging Information Including Gain Loss Recorded on Derivative (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 (Loss) on Fair Value Hedge Item, Net, Total	$ (1)	$ (11)	$ 17	$ (7)
Gain (Loss) on Fair Value Hedges Recognized in Income on Derivative, Total	1	22	(19)	22
Fixed rate borrowings [Member] | Derivative related income (expense) [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Fair Value Gain (Loss) on Hedge Item	(1)	(16)	(2)	(40)
Interest Rate Derivative Fair value Gain (Loss)	1	19	(2)	43
Fixed rate borrowings [Member] | Derivative related income (expense) [Member] | Currency swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Fair Value Gain (Loss) on Hedge Item		5	19	33
Foreign Currency Derivative Fair Value Gain (Loss)		$ 3	$ (17)	$ (21)