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Investment Securities - Additional Information (Details) - USD ($) |  |  | 3 Months Ended | 9 Months Ended
--- | --- | --- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024 | Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |
Accrued interest receivable | $ 302,000,000 | $ 262,000,000 |  |  |  |
Proceeds from sales of securities related to the Transaction |  |  | $ 0 |  | $ 9,696,000,000 | $ 0
Debt securities, available-for-sale, gain (loss) |  |  | 0 | $ (35,000,000) | 0 | (35,000,000)
Proceeds from sales |  |  |  | $ 175,000,000 | 1,000,000 | $ 175,000,000
Investment securities | 37,400,000,000 | 39,400,000,000 | 37,400,000,000 |  | 37,400,000,000 |
Securities received as collateral | $ 1,000,000 | $ 18,000,000 | $ 1,000,000 |  | $ 1,000,000 |
Investment securities available for sale | Government Contracts Concentration Risk | US Treasury and Agency securities |  |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |  |
Percentage of portfolio | 97.00% | 96.00% |  |  |  |

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