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Securities - Amortized Cost and Estimated Fair Value of Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023 | Dec. 31, 2022
--- | --- | --- | --- | ---
Available for sale: |  |  |  |
Available for sale, amortized cost | $ 1,349,979 | $ 1,407,675 |  |
Available for sale, gross unrealized gains | 404 | 297 |  |
Available for sale, gross unrealized losses | (159,461) | (154,341) |  |
Available for sale, fair value | 1,190,922 | 1,253,631 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 1,190,922 | 1,253,631 |  |
Held to maturity: |  |  |  |
Held to maturity, amortized cost | 11,675 |  |  |
Held to maturity, fair value | 10,956 | 10,848 |  |
Held to maturity, allowance for credit losses | (24) | (63) | $ (981) | $ (899)
Held to maturity, net carrying amount | 11,651 | 11,615 |  |
Securities carried at fair value through income: |  |  |  |
Securities carried at fair value through income, fair value | 6,755 | 6,808 |  |
State and municipal securities |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 320,999 | 323,356 |  |
Available for sale, gross unrealized gains | 213 | 210 |  |
Available for sale, gross unrealized losses | (43,615) | (41,440) |  |
Available for sale, fair value | 277,597 | 282,126 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 277,597 | 282,126 |  |
Held to maturity: |  |  |  |
Held to maturity, amortized cost | 11,675 | 11,678 |  |
Held to maturity, gross unrealized gains | 0 | 0 |  |
Held to maturity, gross unrealized losses | (719) | (830) |  |
Held to maturity, fair value | 10,956 | 10,848 |  |
Held to maturity, allowance for credit losses | (24) | (63) |  |
Held to maturity, net carrying amount | 11,651 | 11,615 |  |
Securities carried at fair value through income: |  |  |  |
Securities carried at fair value through income, amortized cost | 6,815 | 6,815 |  |
Securities carried at fair value through income, fair value | 6,755 | 6,808 |  |
Securities carried at fair value through income, net carrying amount | 6,755 | 6,808 |  |
Corporate bonds |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 91,251 | 92,244 |  |
Available for sale, gross unrealized gains | 166 | 80 |  |
Available for sale, gross unrealized losses | (8,170) | (8,689) |  |
Available for sale, fair value | 83,247 | 83,635 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 83,247 | 83,635 |  |
U.S. treasury and government agency securities |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 67,172 | 84,377 |  |
Available for sale, gross unrealized gains | 2 | 3 |  |
Available for sale, gross unrealized losses | (4,736) | (4,740) |  |
Available for sale, fair value | 62,438 | 79,640 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 62,438 | 79,640 |  |
Commercial mortgage-backed securities |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 104,150 | 104,459 |  |
Available for sale, gross unrealized gains | 0 | 0 |  |
Available for sale, gross unrealized losses | (11,410) | (11,063) |  |
Available for sale, fair value | 92,740 | 93,396 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 92,740 | 93,396 |  |
Residential mortgage-backed securities |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 552,647 | 569,622 |  |
Available for sale, gross unrealized gains | 0 | 0 |  |
Available for sale, gross unrealized losses | (66,024) | (63,120) |  |
Available for sale, fair value | 486,623 | 506,502 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 486,623 | 506,502 |  |
Commercial collateralized mortgage obligations |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 45,874 | 39,386 |  |
Available for sale, gross unrealized gains | 0 | 0 |  |
Available for sale, gross unrealized losses | (4,448) | (4,203) |  |
Available for sale, fair value | 41,426 | 35,183 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 41,426 | 35,183 |  |
Residential collateralized mortgage obligations |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 147,310 | 150,710 |  |
Available for sale, gross unrealized gains | 0 | 0 |  |
Available for sale, gross unrealized losses | (20,977) | (20,566) |  |
Available for sale, fair value | 126,333 | 130,144 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | 126,333 | 130,144 |  |
Asset-backed securities |  |  |  |
Available for sale: |  |  |  |
Available for sale, amortized cost | 20,576 | 43,521 |  |
Available for sale, gross unrealized gains | 23 | 4 |  |
Available for sale, gross unrealized losses | (81) | (520) |  |
Available for sale, fair value | 20,518 | 43,005 |  |
Available for sale, allowance for credit losses | 0 | 0 |  |
Available-for-sale, net carrying amount | $ 20,518 | $ 43,005 |  |

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