Investment Securities - Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
AFS, less than 12 months, fair value	$ 8,966	$ 460
AFS, less than 12 months, gross unrealized losses	107	4
AFS, 12 months or longer, fair value	4,243	9,917
AFS, 12 months or longer, gross unrealized losses	132	247
Total investment securities, less than 12 months, fair value	10,051	2,011
Total investment securities, less than 12 months, gross unrealized losses	127	27
Total investment securities, 12 months or longer, fair value	16,013	21,761
Total investment securities, 12 months or longer, gross unrealized losses	1,361	1,259
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	1,085	1,551
HTM, Less than 12 months, gross unrealized losses	20	23
HTM, 12 months or longer, fair value	11,770	11,844
HTM, 12 months or longer, gross unrealized losses	1,229	1,012
U.S. Treasury
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
AFS, less than 12 months, fair value	1,971	229
AFS, less than 12 months, gross unrealized losses	9	1
AFS, 12 months or longer, fair value	2,554	7,474
AFS, 12 months or longer, gross unrealized losses	18	112
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	50	50
HTM, Less than 12 months, gross unrealized losses	0	0
HTM, 12 months or longer, fair value	951	924
HTM, 12 months or longer, gross unrealized losses	14	31
Commercial
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
AFS, less than 12 months, fair value	2,566	74
AFS, less than 12 months, gross unrealized losses	45	1
AFS, 12 months or longer, fair value	64	330
AFS, 12 months or longer, gross unrealized losses	0	8
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	0	328
HTM, Less than 12 months, gross unrealized losses	0	9
HTM, 12 months or longer, fair value	1,877	1,575
HTM, 12 months or longer, gross unrealized losses	157	121
Residential
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
AFS, less than 12 months, fair value	4,429	151
AFS, less than 12 months, gross unrealized losses	53	2
AFS, 12 months or longer, fair value	1,623	1,959
AFS, 12 months or longer, gross unrealized losses	114	116
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	996	955
HTM, Less than 12 months, gross unrealized losses	19	11
HTM, 12 months or longer, fair value	6,811	7,139
HTM, 12 months or longer, gross unrealized losses	942	791
Other
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract]
AFS, less than 12 months, fair value	0	6
AFS, less than 12 months, gross unrealized losses	0	0
AFS, 12 months or longer, fair value	2	154
AFS, 12 months or longer, gross unrealized losses	0	11
State and political subdivisions
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	39	218
HTM, Less than 12 months, gross unrealized losses	1	3
HTM, 12 months or longer, fair value	2,131	2,172
HTM, 12 months or longer, gross unrealized losses	116	64
Privately issued
Schedule of Held-to-Maturity Securities [Line Items]
HTM, less than 12 months, fair value	0	0
HTM, Less than 12 months, gross unrealized losses	0	0
HTM, 12 months or longer, fair value	0	34
HTM, 12 months or longer, gross unrealized losses	$ 0	$ 5