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Investment Securities - Securities With Unrealized Losses (Details) $ in Thousands | Sep. 30, 2023 USD ($)
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Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | $ 45,424
Available-for-sale, less than 12 months, gross unrealized losses | (4,168)
Available-for-sale, 12 months or more, estimated fair value | 3,282,758
Available-for-sale, 12 months or more, gross unrealized losses | (526,085)
Available-for-sale, total, estimated fair value | 3,328,182
Available-for-sale, total, gross unrealized losses | (530,253)
U.S. Treasury |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 0
Available-for-sale, less than 12 months, gross unrealized losses | 0
Available-for-sale, 12 months or more, estimated fair value | 2,224
Available-for-sale, 12 months or more, gross unrealized losses | (54)
Available-for-sale, total, estimated fair value | 2,224
Available-for-sale, total, gross unrealized losses | (54)
U.S. Government agencies |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 9,161
Available-for-sale, less than 12 months, gross unrealized losses | (21)
Available-for-sale, 12 months or more, estimated fair value | 158,972
Available-for-sale, 12 months or more, gross unrealized losses | (6,903)
Available-for-sale, total, estimated fair value | 168,133
Available-for-sale, total, gross unrealized losses | (6,924)
Mortgage-backed securities |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 9,924
Available-for-sale, less than 12 months, gross unrealized losses | (140)
Available-for-sale, 12 months or more, estimated fair value | 2,147,168
Available-for-sale, 12 months or more, gross unrealized losses | (287,571)
Available-for-sale, total, estimated fair value | 2,157,092
Available-for-sale, total, gross unrealized losses | (287,711)
State and political subdivisions |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 11,170
Available-for-sale, less than 12 months, gross unrealized losses | (502)
Available-for-sale, 12 months or more, estimated fair value | 771,404
Available-for-sale, 12 months or more, gross unrealized losses | (208,638)
Available-for-sale, total, estimated fair value | 782,574
Available-for-sale, total, gross unrealized losses | (209,140)
Other securities |
Debt Securities, Available-for-sale [Line Items] |
Available-for-sale, less than 12 months, estimated fair value | 15,169
Available-for-sale, less than 12 months, gross unrealized losses | (3,505)
Available-for-sale, 12 months or more, estimated fair value | 202,990
Available-for-sale, 12 months or more, gross unrealized losses | (22,919)
Available-for-sale, total, estimated fair value | 218,159
Available-for-sale, total, gross unrealized losses | $ (26,424)

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