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, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 50	$ (418)	$ (541)
Gain (Loss) on Hedged Items	(49)	378	383
Securities available-for-sale ("AFS") | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	129	(731)	(776)
Gain (Loss) on Hedged Items	(29)	900	1,086
Deposits | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(49)	148
Gain (Loss) on Hedged Items	(6)	(261)
Long-term Debt | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(30)	165	235
Gain (Loss) on Hedged Items	$ (14)	$ (261)	$ (703)