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Relationship with Bayview Lending Group LLC and Bayview Financial Holdings, L.P. - Additional Information (Detail) - USD ($) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2024 | Sep. 30, 2023 | Dec. 31, 2023
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Revenue from contract with customer | $ 394,000,000 | $ 360,000,000 | $ 1,149,000,000 | $ 1,119,000,000 |
Loan facility carrying amount | $ 11,583,000,000 |  | $ 11,583,000,000 |  | $ 8,201,000,000
Bayview Lending Group |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership percentage (as a percent) | 20.00% |  | 20.00% |  |
Equity method investments | $ 0 |  | $ 0 |  |
Bayview Lending Group | Other Revenues From Operations |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Income from equity method investments |  |  | 25,000,000 | 20,000,000 |
Bayview Lending Group and Bayview Financial |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Outstanding principal balances of mortgage servicing rights | 1,100,000,000 |  | 1,100,000,000 |  | 1,200,000,000
Revenue from contract with customer | 1,000,000 | 1,000,000 | 4,000,000 | 5,000,000 |
Bayview Financial |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Outstanding principal balances of residential mortgage loans from Bayview Financial | 112,700,000,000 |  | 112,700,000,000 |  | 115,300,000,000
Revenues from sub-servicing | 29,000,000 | $ 30,000,000 | 92,000,000 | $ 94,000,000 |
Investment securities in held-to-maturity portfolio securitized by Bayview Financial | 38,000,000 |  | 38,000,000 |  | $ 42,000,000
Bayview Financial | Syndicated Loan Facility |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Loan facility carrying amount | 3,000,000,000.0 |  | 3,000,000,000.0 |  |
Bayview Financial | Syndicated Loan Facility | M&T Bank |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Loan facility carrying amount | $ 510,000,000 |  | $ 510,000,000 |  |

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