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Investment Securities - Gross unrealized losses (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2023 USD ($) security | Dec. 31, 2022 USD ($) security | Dec. 31, 2021 USD ($)
Investment securities available-for-sale |  |  |
Number of Holdings | security | 129 | 183 |
Unrealized losses less than 12 months | $ (3) | $ (19,761) |
Fair value less than 12 months | 532 | 178,719 |
Unrealized losses over 12 months | (98,020) | (112,503) |
Fair value over 12 months | 485,527 | 535,024 |
Total Unrealized losses | (98,023) | (132,264) |
Total Fair value | 486,059 | $ 713,743 |
Held-to-maturity investment securities |  |  |
Number of Holdings | security |  | 208 |
Unrealized losses less than 12 months |  | $ (3,336) |
Fair value less than 12 months |  | 18,788 |
Unrealized losses over 12 months |  | (47,654) |
Fair value over 12 months |  | 249,623 |
Total Unrealized losses |  | (50,990) |
Total Fair value |  | 268,411 |
Unrealized losses less than 12 months |  | (23,097) |
Fair value less than 12 months |  | 197,507 |
Unrealized losses over 12 months |  | (160,157) |
Fair value over 12 months |  | $ 784,647 |
Total available for sale and held to maturity | security |  | 391 |
Total Unrealized losses |  | $ (183,254) |
Total Fair value |  | 982,154 |
Held to Maturity, Excluding Accrued Interest, Past Due | 0 | 0 |
Held-to-maturity interest income | $ 0 | $ 0 | $ 0
U.S. treasury and government agencies |  |  |
Investment securities available-for-sale |  |  |
Number of Holdings | security | 1 | 1 |
Unrealized losses less than 12 months | $ (3) | $ (17) |
Fair value less than 12 months | 489 | 509 |
Total Unrealized losses | (3) | (17) |
Total Fair value | $ 489 | $ 509 |
Mortgage backed securities - Residential agency |  |  |
Investment securities available-for-sale |  |  |
Number of Holdings | security | 112 | 145 |
Unrealized losses less than 12 months |  | $ (10,457) |
Fair value less than 12 months | $ 43 | 79,693 |
Unrealized losses over 12 months | (88,547) | (107,711) |
Fair value over 12 months | 435,505 | 507,418 |
Total Unrealized losses | (88,547) | (118,168) |
Total Fair value | $ 435,548 | $ 587,111 |
Held-to-maturity investment securities |  |  |
Number of Holdings | security |  | 27 |
Unrealized losses over 12 months |  | $ (33,254) |
Fair value over 12 months |  | 150,861 |
Total Unrealized losses |  | (33,254) |
Total Fair value |  | $ 150,861 |
Mortgage backed securities - Commercial |  |  |
Investment securities available-for-sale |  |  |
Number of Holdings | security | 1 | 17 |
Unrealized losses less than 12 months |  | $ (4,835) |
Fair value less than 12 months |  | 50,437 |
Unrealized losses over 12 months | $ (123) | (2,276) |
Fair value over 12 months | 1,353 | 13,120 |
Total Unrealized losses | (123) | (7,111) |
Total Fair value | $ 1,353 | $ 63,557 |
Asset backed securities |  |  |
Investment securities available-for-sale |  |  |
Number of Holdings | security | 3 | 3 |
Fair value less than 12 months |  | $ 32 |
Unrealized losses over 12 months | $ (1) |  |
Fair value over 12 months | 25 | 2 |
Total Unrealized losses | (1) |  |
Total Fair value | $ 25 | $ 34 |
Corporate bonds |  |  |
Investment securities available-for-sale |  |  |
Number of Holdings | security | 12 | 17 |
Unrealized losses less than 12 months |  | $ (4,452) |
Fair value less than 12 months |  | 48,048 |
Unrealized losses over 12 months | $ (9,349) | (2,516) |
Fair value over 12 months | 48,644 | 14,484 |
Total Unrealized losses | (9,349) | (6,968) |
Total Fair value | $ 48,644 | 62,532 |
Obligations of state and political agencies. |  |  |
Investment securities available-for-sale |  |  |
Unrealized losses less than 12 months |  | (3,336) |
Fair value less than 12 months |  | 18,788 |
Unrealized losses over 12 months |  | (14,400) |
Fair value over 12 months |  | 98,762 |
Total Unrealized losses |  | (17,736) |
Total Fair value |  | $ 117,550 |
Held-to-maturity investment securities |  |  |
Number of Holdings | security |  | 181 |

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