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Securities - Additional Information (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2025 USD ($) Security | Sep. 30, 2024 USD ($) | Jun. 30, 2024 USD ($) shares | Sep. 30, 2025 USD ($) Security Segment | Sep. 30, 2024 USD ($) | Dec. 31, 2024 USD ($) Security
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Number of Investment Securities Segments | Segment |  |  |  | 2 |  |
Credit losses |  |  |  | $ 0 |  |
Municipal securities percentage of securities portfolio | 0.70% |  |  | 0.70% |  |
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year | Security | 756 |  |  | 756 |  | 949
Gain (loss) on sale of investment securities | $ 0 | $ 0 |  | $ 0 | $ (9,400,000) |
Available for Sale Securities, Amortized Cost Basis | 334,356,000 |  |  | 334,356,000 |  | $ 339,016,000
Debt Securities, Available-for-Sale | 332,369,000 |  |  | 332,369,000 |  | 336,960,000
Collateralized Securities [Member] |  |  |  |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Available for Sale Securities, Amortized Cost Basis | 7,510,000,000 |  |  | 7,510,000,000 |  | 10,260,000,000
Debt Securities, Available-for-Sale | $ 6,780,000,000 |  |  | $ 6,780,000,000 |  | $ 8,910,000,000
Visa Stock Exchange [Member] |  |  |  |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Conversion of stock, description |  |  |  | During the second quarter of 2024, the Bank tendered all of its shares of Visa Class B-1 common stock in exchange for a combination of Visa Class B-2 common stock and Visa Class C common stock, pursuant to the terms and subject to the conditions of the public offering of Visa to exchange its Class B-1 common stock for a combination of shares of its Class B-2 common stock and Class C common stock, which expired on May 3, 2024. |  |
Gain on stock exchange |  |  | $ 20,600,000 |  |  |
Class B-2 Common Stock [Member] | Visa Stock Exchange [Member] |  |  |  |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Conversion of stock, shares converted | shares |  |  | 48,492 |  |  |
Cost basis |  |  | $ 0 |  |  |
Common Class C [Member] | Visa Stock Exchange [Member] |  |  |  |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Conversion of stock, shares converted | shares |  |  | 19,245 |  |  |
Securities Concentration Risk [Member] | Stockholders' Equity, Total [Member] | Other Than U.S. Government and Agencies [Member] |  |  |  |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |  |  |  |
Concentration Risk, Percentage |  |  |  | 10.00% |  | 10.00%

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