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Investment Securities - Investment Securities in Continuous Unrealized Loss Position (Detail) - USD ($) $ in Millions | Jun. 30, 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 | $ 4,786 | $ 460
AFS, less than 12 months, gross unrealized losses | 36 | 4
AFS, 12 months or longer, fair value | 6,655 | 9,917
AFS, 12 months or longer, gross unrealized losses | 215 | 247
Total investment securities, less than 12 months, fair value | 5,621 | 2,011
Total investment securities, less than 12 months, gross unrealized losses | 50 | 27
Total investment securities, 12 months or longer, fair value | 19,270 | 21,761
Total investment securities, 12 months or longer, gross unrealized losses | 1,492 | 1,259
Schedule of Held-to-Maturity Securities [Line Items] |  |
HTM, less than 12 months, fair value | 835 | 1,551
HTM, Less than 12 months, gross unrealized losses | 14 | 23
HTM, 12 months or longer, fair value | 12,615 | 11,844
HTM, 12 months or longer, gross unrealized losses | 1,277 | 1,012
U.S. Treasury and federal agencies |  |
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
AFS, less than 12 months, fair value | 2,586 | 229
AFS, less than 12 months, gross unrealized losses | 15 | 1
AFS, 12 months or longer, fair value | 4,400 | 7,474
AFS, 12 months or longer, gross unrealized losses | 70 | 112
Schedule of Held-to-Maturity Securities [Line Items] |  |
HTM, less than 12 months, fair value | 0 | 50
HTM, Less than 12 months, gross unrealized losses | 0 | 0
HTM, 12 months or longer, fair value | 980 | 924
HTM, 12 months or longer, gross unrealized losses | 30 | 31
Commercial |  |
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
AFS, less than 12 months, fair value | 1,061 | 74
AFS, less than 12 months, gross unrealized losses | 10 | 1
AFS, 12 months or longer, fair value | 317 | 330
AFS, 12 months or longer, gross unrealized losses | 6 | 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 | 1,880 | 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 | 1,129 | 151
AFS, less than 12 months, gross unrealized losses | 11 | 2
AFS, 12 months or longer, fair value | 1,874 | 1,959
AFS, 12 months or longer, gross unrealized losses | 137 | 116
Schedule of Held-to-Maturity Securities [Line Items] |  |
HTM, less than 12 months, fair value | 790 | 955
HTM, Less than 12 months, gross unrealized losses | 13 | 11
HTM, 12 months or longer, fair value | 7,510 | 7,139
HTM, 12 months or longer, gross unrealized losses | 959 | 791
Other debt securities |  |
Debt Securities, Available-for-Sale, Unrealized Loss Position, Accumulated Loss [Abstract] |  |
AFS, less than 12 months, fair value | 10 | 6
AFS, less than 12 months, gross unrealized losses | 0 | 0
AFS, 12 months or longer, fair value | 64 | 154
AFS, 12 months or longer, gross unrealized losses | 2 | 11
Obligations of states and political subdivisions |  |
Schedule of Held-to-Maturity Securities [Line Items] |  |
HTM, less than 12 months, fair value | 45 | 218
HTM, Less than 12 months, gross unrealized losses | 1 | 3
HTM, 12 months or longer, fair value | 2,214 | 2,172
HTM, 12 months or longer, gross unrealized losses | 126 | 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 | 31 | 34
HTM, 12 months or longer, gross unrealized losses | $ 5 | $ 5

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