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Securities (Securities Moody's and Standard & Poor's Bond Rating) (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
--- | --- | ---
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | $ 3,534,085 | $ 3,619,738
States and Political Subdivisions [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 2,338,745 | 2,367,807
States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 799,508 |
States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 1,504,951 |
States and Political Subdivisions [Member] | Guaranteed by Third Party |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 19,755 |
States and Political Subdivisions [Member] | Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 14,531 |
Other [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 1,500 | $ 1,500
Aaa/AAA [Member] | States and Political Subdivisions [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 1,834,432 |
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 301,310 |
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 1,504,951 |
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 13,640 |
Aaa/AAA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 14,531 |
Aaa/AAA [Member] | Other [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Aa/AA [Member] | States and Political Subdivisions [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 504,313 |
Aa/AA [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 498,198 |
Aa/AA [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Aa/AA [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 6,115 |
Aa/AA [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Aa/AA [Member] | Other [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | States and Political Subdivisions [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | States and Political Subdivisions [Member] | Not Guaranteed or Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | States and Political Subdivisions [Member] | Guaranteed by the Texas PSF [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | States and Political Subdivisions [Member] | Guaranteed by Third Party |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | States and Political Subdivisions [Member] | Pre-Refunded [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | 0 |
Not rated [Member] | Other [Member] |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Held to Maturity, Amortized Cost | $ 1,500 |

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