Derivative Financial Instruments - Derivative Fair Values in Consolidated Balance Sheet for Our Non-Qualifying Hedges (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Total Derivative Instruments Not Designated As Hedging Instruments Asset At Fair Value	$ (1,091)		$ (888)
Total Derivative Instruments Not Designated As Hedging Instruments Liability At Fair Value	4		9
Interest rate swaps [Member] | Derivative Related Liabilities [Member]
Derivatives, Fair Value [Line Items]
Liability Derivatives Fair Value, non-qualifying hedges	4		5
Interest rate swaps [Member] | Derivative financial assets [Member]
Derivatives, Fair Value [Line Items]
Asset Derivatives Fair Value, non-qualifying hedges	(1,084)	[1]	(926)	[1]
Currency swaps and foreign exchange forward contracts [Member] | Derivative Related Liabilities [Member]
Derivatives, Fair Value [Line Items]
Foreign currency derivative instruments not designated as hedging instruments, liability at fair value			4
Currency swaps and foreign exchange forward contracts [Member] | Derivative financial assets [Member]
Derivatives, Fair Value [Line Items]
Foreign currency derivative instruments not designated as hedging instruments, asset at fair value	$ (7)	[1]	$ 38	[1]

[1] At December 31, 2012 and December 31, 2011, derivative financial assets are reported on our consolidated balance sheet within other assets.