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Loans and leases and allowance for credit losses - Summary of Payment Status of Loans Modified (Detail) - USD ($) $ in Millions | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | $ 1,130 | $ 1,586
Current |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 953 | 1,414
30-89 Days Past Due |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 117 | 123
Accruing Loans Past Due 90 Days or More |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 60 | 49
Commercial and industrial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 303 | 198
Commercial and industrial | Current |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 276 | 182
Commercial and industrial | 30-89 Days Past Due |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 14 | 7
Commercial and industrial | Accruing Loans Past Due 90 Days or More |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 13 | 9
Commercial Real Estate | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 515 | 651
Commercial Real Estate | Residential builder and developer |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 2 | 71
Commercial Real Estate | Other commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 130 | 488
Commercial Real Estate | Current | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 478 | 618
Commercial Real Estate | Current | Residential builder and developer |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 1 | 71
Commercial Real Estate | Current | Other commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 101 | 440
Commercial Real Estate | 30-89 Days Past Due | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 37 | 21
Commercial Real Estate | 30-89 Days Past Due | Residential builder and developer |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Commercial Real Estate | 30-89 Days Past Due | Other commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 25 | 48
Commercial Real Estate | Accruing Loans Past Due 90 Days or More | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 12
Commercial Real Estate | Accruing Loans Past Due 90 Days or More | Residential builder and developer |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 1 | 0
Commercial Real Estate | Accruing Loans Past Due 90 Days or More | Other commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 4 | 0
Residential Real Estate | Residential |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 177 | 177
Residential Real Estate | Current | Residential |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 94 | 102
Residential Real Estate | 30-89 Days Past Due | Residential |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 41 | 47
Residential Real Estate | Accruing Loans Past Due 90 Days or More | Residential |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 42 | 28
Consumer: | Home equity lines and loans |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 2 | 1
Consumer: | Recreational finance |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 1 | 0
Consumer: | Automobile |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Other |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Current | Home equity lines and loans |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 2 | 1
Consumer: | Current | Recreational finance |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 1 | 0
Consumer: | Current | Automobile |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Current | Other |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | 30-89 Days Past Due | Home equity lines and loans |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | 30-89 Days Past Due | Recreational finance |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | 30-89 Days Past Due | Automobile |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | 30-89 Days Past Due | Other |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Accruing Loans Past Due 90 Days or More | Home equity lines and loans |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Accruing Loans Past Due 90 Days or More | Recreational finance |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Accruing Loans Past Due 90 Days or More | Automobile |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | 0 | 0
Consumer: | Accruing Loans Past Due 90 Days or More | Other |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Amortized cost | $ 0 | $ 0

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