Derivative Financial Instruments - Gain or Loss Recorded on Our Non-Qualifying Hedges (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
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	$ 180	$ (424)	$ 263	$ (216)
Interest Rate Contracts [Member] | Derivative related income (expense) [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	181	(424)	264	(212)
Currency contracts [Member] | Derivative related income (expense) [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	$ (1)	$ 0	$ (1)	$ (4)