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Investment Securities - Gross unrealized losses (Details) - USD ($) $ in Thousands | Jun. 30, 2023 | Dec. 31, 2022
--- | --- | ---
Investment securities available-for-sale |  |
Unrealized losses less than 12 months | $ (995) | $ (19,761)
Fair value less than 12 months | 10,274 | 178,719
Unrealized losses over 12 months | (135,968) | (112,503)
Fair value over 12 months | 664,644 | 535,024
Total Unrealized losses | (136,963) | (132,264)
Total Fair value | 674,918 | 713,743
Held-to-maturity investment securities |  |
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 Unrealized losses |  | (183,254)
Total Fair value |  | 982,154
U. S. Treasury and agencies |  |
Investment securities available-for-sale |  |
Unrealized losses less than 12 months | (20) | (17)
Fair value less than 12 months | 420 | 509
Total Unrealized losses | (20) | (17)
Total Fair value | 420 | 509
Mortgage backed securities - Residential agency |  |
Investment securities available-for-sale |  |
Unrealized losses less than 12 months | (76) | (10,457)
Fair value less than 12 months | 2,148 | 79,693
Unrealized losses over 12 months | (115,055) | (107,711)
Fair value over 12 months | 556,258 | 507,418
Total Unrealized losses | (115,131) | (118,168)
Total Fair value | 558,406 | 587,111
Held-to-maturity investment securities |  |
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 |  |
Unrealized losses less than 12 months | (32) | (4,835)
Fair value less than 12 months | 570 | 50,437
Unrealized losses over 12 months | (7,438) | (2,276)
Fair value over 12 months | 60,339 | 13,120
Total Unrealized losses | (7,470) | (7,111)
Total Fair value | 60,909 | 63,557
Asset backed securities |  |
Investment securities available-for-sale |  |
Fair value less than 12 months | 27 | 32
Fair value over 12 months | 1 | 2
Total Fair value | 28 | 34
Corporate bonds |  |
Investment securities available-for-sale |  |
Unrealized losses less than 12 months | (867) | (4,452)
Fair value less than 12 months | 7,109 | 48,048
Unrealized losses over 12 months | (13,475) | (2,516)
Fair value over 12 months | 48,046 | 14,484
Total Unrealized losses | (14,342) | (6,968)
Total Fair value | $ 55,155 | 62,532
Obligations of state and political agencies. |  |
Held-to-maturity investment securities |  |
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

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