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		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives	$ (27)	$ (164)	$ (208)	$ (102)
Gain (Loss) Reclassified From AOCI into Income	(16)	(22)	(43)	(45)
Foreign exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives	2	6	(1)	5
Foreign exchange contracts | Net interest income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified From AOCI into Income	0	0	0	0
Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Recognized in AOCI on Derivatives	(29)	(170)	(207)	(107)
Interest rate contracts | Net interest income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Reclassified From AOCI into Income	$ (16)	$ (22)	$ (43)	$ (45)