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v3.25.0.1

Relationship with BLG and Bayview Financial - Additional Information (Detail) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Feb. 19, 2025
Schedule of Equity Method Investments [Line Items] |  |  |  |
Long-term borrowings | $ 12,605,000,000 | $ 8,201,000,000 |  |
Loans and leases | 135,581,000,000 | 134,068,000,000 |  |
Commercial Portfolio Segment |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Loans and leases | $ 61,481,000,000 | 57,010,000,000 |  |
Bayview Lending Group |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Ownership percentage (as a percent) | 20.00% |  |  |
Equity method investments | $ 0 |  |  |
Bayview Lending Group | Other Revenues From Operations |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Income from BLG | 48,000,000 | 20,000,000 | $ 30,000,000 |
Bayview Lending Group and Bayview Financial |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Outstanding principal balances of mortgage servicing rights | 1,000,000,000.0 | 1,200,000,000 |  |
Revenue from contract with customer | 5,000,000 | 6,000,000 | 8,000,000 |
Bayview Financial |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Outstanding principal balances of residential mortgage loans from Bayview Financial | 111,500,000,000 | 115,300,000,000 |  |
Revenues from sub-servicing | 123,000,000 | 125,000,000 | $ 154,000,000 |
Investment securities in held-to-maturity portfolio securitized by Bayview Financial | 37,000,000 | $ 42,000,000 |  |
Bayview Financial | Subsequent Event |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Outstanding principal balances of residential mortgage loans from Bayview Financial |  |  |  | $ 51,700,000,000
Bayview Financial | Subsequent Event | Commercial Portfolio Segment |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Loans and leases |  |  |  | $ 333,000,000
Bayview Financial | Syndicated Loan Facility |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Long-term borrowings | 2,700,000,000 |  |  |
Bayview Financial | Syndicated Loan Facility | M&T Bank |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |
Long-term borrowings | $ 404,000,000 |  |  |

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