Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (Detail) - Net interest income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 311	$ 1,554	$ 50
Gain (Loss) on Hedged Items	(188)	(1,437)	(49)
Asset-backed securities available-for-sale | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	348	2,219	129
Gain (Loss) on Hedged Items	386	(1,871)	(29)
Deposits | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(22)	(138)	(49)
Gain (Loss) on Hedged Items	(113)	56	(6)
Long-term debt | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(15)	(527)	(30)
Gain (Loss) on Hedged Items	$ (461)	$ 378	$ (14)