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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	$ 638	$ (308)	$ 996	$ 146
Gain (Loss) on Hedged Items	(607)	308	(972)	(143)
Securities available-for-sale | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	748	(382)	1,407	192
Gain (Loss) on Hedged Items	(679)	407	(1,321)	(140)
Deposits | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(20)	11	(85)	(32)
Gain (Loss) on Hedged Items	3	(21)	54	8
Long-term debt | Interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) on Derivatives	(90)	63	(326)	(14)
Gain (Loss) on Hedged Items	$ 69	$ (78)	$ 295	$ (11)