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Investment Securities - Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
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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

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