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Securities - Additional Information (Details) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2024 USD ($) Segment Security | Mar. 31, 2023 USD ($) | Dec. 31, 2023 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 | 0.90% |  |
Securities in Unrealized Loss Positions Qualitative Disclosure Number of Positions Greater Than or Equal to One Year | Security | 1,028 |  | 941
Gain (loss) on sale of securities | $ 298,000 | $ 0 |
Available for Sale Securities, Amortized Cost Basis | 318,253,000 |  | $ 440,358,000
Debt Securities, Available-for-Sale | 315,300,000 |  | 438,588,000
Collateralized Securities [Member] |  |  |
Schedule Of Held To Maturity Securities [Line Items] |  |  |
Available for Sale Securities, Amortized Cost Basis | 10,990,000,000 |  | 11,340,000,000
Debt Securities, Available-for-Sale | $ 9,600,000,000 |  | $ 10,090,000,000.00
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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