Derivative Financial Instruments - Location of Derivative Fair Values in Consolidated Balance Sheet (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Derivative related assets at fair value	$ 7		$ 64
Derivative related liabilities at fair value	0		7
Derivative financial assets [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Asset Derivatives Fair Value	7	[1]	11	[1]
Derivative financial assets [Member] | Currency swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Asset Derivatives Fair Value	0	[1]	53	[1]
Derivative Related Liabilities [Member] | Interest rate swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative related liabilities at fair value	0		7
Derivative Related Liabilities [Member] | Currency swaps [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Liability Derivatives Fair Value	$ 0		$ 0

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