Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (Detail) - Net interest income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 220	$ 638	$ 95	$ 996
Gain (Loss) on Hedged Items	(194)	(607)	(19)	(972)
Asset-backed securities available-for-sale | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	399	748	192	1,407
Gain (Loss) on Hedged Items	(220)	(679)	166	(1,321)
Deposits | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(33)	(20)	(27)	(85)
Gain (Loss) on Hedged Items	(1)	3	(38)	54
Long-term debt | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(146)	(90)	(70)	(326)
Gain (Loss) on Hedged Items	$ 27	$ 69	$ (147)	$ 295