Derivative Financial Instruments - Gains and Losses on Hedged Items in Fair Value Hedges (Detail) - Net interest income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 358	$ 454
Gain (Loss) on Hedged Items	(365)	(451)
Securities available-for-sale ("AFS") | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	659	574
Gain (Loss) on Hedged Items	(642)	(547)
Deposits | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(65)	(43)
Gain (Loss) on Hedged Items	51	29
Long-term debt | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(236)	(77)
Gain (Loss) on Hedged Items	$ 226	$ 67