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Investment Securities - Securities With Unrealized Losses (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
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Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | $ 27,841 | $ 37,952
Available-for-sale, less than 12 months, gross unrealized losses | (303) | (411)
Available-for-sale, 12 months or more, estimated fair value | 2,384,386 | 2,429,271
Available-for-sale, 12 months or more, gross unrealized losses | (337,094) | (323,244)
Available-for-sale, total, estimated fair value | 2,412,227 | 2,467,223
Available-for-sale, total, gross unrealized losses | (337,397) | (323,655)
U.S. Treasury |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | 0 | 0
Available-for-sale, less than 12 months, gross unrealized losses | 0 | 0
Available-for-sale, 12 months or more, estimated fair value | 699 | 996
Available-for-sale, 12 months or more, gross unrealized losses | (1) | (3)
Available-for-sale, total, estimated fair value | 699 | 996
Available-for-sale, total, gross unrealized losses | (1) | (3)
U.S. Government agencies |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | 1,708 | 717
Available-for-sale, less than 12 months, gross unrealized losses | (21) | (7)
Available-for-sale, 12 months or more, estimated fair value | 49,184 | 51,186
Available-for-sale, 12 months or more, gross unrealized losses | (837) | (1,040)
Available-for-sale, total, estimated fair value | 50,892 | 51,903
Available-for-sale, total, gross unrealized losses | (858) | (1,047)
Mortgage-backed securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | 7,055 | 7,480
Available-for-sale, less than 12 months, gross unrealized losses | (15) | (189)
Available-for-sale, 12 months or more, estimated fair value | 1,364,722 | 1,384,532
Available-for-sale, 12 months or more, gross unrealized losses | (127,755) | (152,595)
Available-for-sale, total, estimated fair value | 1,371,777 | 1,392,012
Available-for-sale, total, gross unrealized losses | (127,770) | (152,784)
State and political subdivisions |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | 14,153 | 16,843
Available-for-sale, less than 12 months, gross unrealized losses | (192) | (195)
Available-for-sale, 12 months or more, estimated fair value | 806,319 | 829,754
Available-for-sale, 12 months or more, gross unrealized losses | (198,387) | (157,374)
Available-for-sale, total, estimated fair value | 820,472 | 846,597
Available-for-sale, total, gross unrealized losses | (198,579) | (157,569)
Other securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Available-for-sale, less than 12 months, estimated fair value | 4,925 | 12,912
Available-for-sale, less than 12 months, gross unrealized losses | (75) | (20)
Available-for-sale, 12 months or more, estimated fair value | 163,462 | 162,803
Available-for-sale, 12 months or more, gross unrealized losses | (10,114) | (12,232)
Available-for-sale, total, estimated fair value | 168,387 | 175,715
Available-for-sale, total, gross unrealized losses | $ (10,189) | $ (12,252)

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