Derivative Financial Instruments - Gains and Losses on Derivative Instruments Designated and Qualifying As Hedging Instruments in Cash Flow Hedges (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives(1)	$ 8
Gain (Loss) Recognized in AOCI on Derivatives(1)		$ (2)
Gain (Loss) Reclassified From AOCI into Income(1)	(10)
Gain (Loss) Reclassified From AOCI into Income(1)		(4)
Foreign exchange contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives(1)	1
Gain (Loss) Recognized in AOCI on Derivatives(1)		(5)
Foreign exchange contracts [Member] | Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified From AOCI into Income(1)	0
Gain (Loss) Reclassified From AOCI into Income(1)		0
Interest rate contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives(1)	7
Gain (Loss) Recognized in AOCI on Derivatives(1)		3
Interest rate contracts [Member] | Interest Income Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified From AOCI into Income(1)	$ (10)
Gain (Loss) Reclassified From AOCI into Income(1)		$ (4)