Derivative Financial Instruments - Gains and Losses on Derivative Instruments Designated and Qualifying As Hedging Instruments in Cash Flow Hedges (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion)	$ (35)	$ 34
Gain (Loss) Reclassed From AOCI into Income (Effective Portion)	(1)	(4)
Gain (Loss) Recognized in Income on the Derivative (Ineffective Portion)	0	0
Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on the Derivative (Ineffective Portion)	(6)	(4)
Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion)	1	0
Foreign exchange contracts [Member] | Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassed From AOCI into Income (Effective Portion)	0	0
Foreign exchange contracts [Member] | Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on the Derivative (Ineffective Portion)	0	0
Interest rate contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivative (Effective Portion)	(36)	34
Interest rate contracts [Member] | Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassed From AOCI into Income (Effective Portion)	(1)	(4)
Interest rate contracts [Member] | Other Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in Income on the Derivative (Ineffective Portion)	$ 0	$ 0