Derivative Financial Instruments - Gain or Loss Recorded on Derivatives Related to Fair Value Option Debt Primarily Due to Changes in Interest Rates (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]
Total	$ 52	$ 297	$ 118	$ 446
Interest rate component [Member] | Gain (loss) on debt designated at fair value and related derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest Rate Derivative Fair value Gain (Loss)	30	128	70	264
Currency contracts [Member] | Gain (loss) on debt designated at fair value and related derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Foreign Currency Derivative Fair Value Gain (Loss)	$ 22	$ 169	$ 48	$ 182