Derivative Financial Instruments - Gain or Loss Recorded on Our Non-Qualifying Hedges (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	$ (317)	$ 315	$ (227)
Interest Rate Contracts [Member] | Derivative related income (expense) [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	(317)	315	(221)
Currency Contracts [Member] | Derivative related income (expense) [Member]
Derivatives, Fair Value [Line Items]
Amount of Gain (Loss) Recognized in Derivative Related Income (Expense)	$ 0	$ 0	$ (6)