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Investment Securities - Schedule of HTM Portfolio (Details) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
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Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | $ 3,594,745 | $ 3,639,850
State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 1,855,816 | 1,857,373
Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 257,388 | $ 256,576
Aaa/AAA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 476,277 |
Aaa/AAA | Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Aa/AA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 1,160,822 |
Aa/AA | Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
A | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 198,951 |
A | Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 103,765 |
Baa/BBB | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 4,391 |
Baa/BBB | Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 153,623 |
Not Rated | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 15,375 |
Not Rated | Other securities |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Not Guaranteed or Pre-Refunded | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 862,320 |
Not Guaranteed or Pre-Refunded | Aaa/AAA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 182,733 |
Not Guaranteed or Pre-Refunded | Aa/AA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 626,037 |
Not Guaranteed or Pre-Refunded | A | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 38,175 |
Not Guaranteed or Pre-Refunded | Baa/BBB | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Not Guaranteed or Pre-Refunded | Not Rated | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 15,375 |
Other Credit Enhancement or Insurance | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 993,496 |
Other Credit Enhancement or Insurance | Aaa/AAA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 293,544 |
Other Credit Enhancement or Insurance | Aa/AA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 534,785 |
Other Credit Enhancement or Insurance | A | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 160,776 |
Other Credit Enhancement or Insurance | Baa/BBB | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 4,391 |
Other Credit Enhancement or Insurance | Not Rated | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | Aaa/AAA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | Aa/AA | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | A | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | Baa/BBB | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | 0 |
Pre-Refunded | Not Rated | State and political subdivisions |  |
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items] |  |
Amortized Cost | $ 0 |

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