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Note 3 - Investment Securities - Gross Unrealized Losses, Investment Securities Portfolio (Details) $ in Thousands | Mar. 31, 2025 USD ($) | Dec. 31, 2024 USD ($)
--- | --- | ---
Available for sale securities, less than 12 months, number of investment positions | 19 | 22
Held to Maturity securities, less than 12 months, number of investment positions | 31 | 47
Available for sale securities, less than 12 months, fair value | $ 62,320 | $ 66,670
Held to Maturity securities, less than 12 months, fair value | 176,050 | 267,612
Available for sale securities, less than 12 months, unrealized loss | (510) | (692)
Held to Maturity securities, less than 12 months, unrealized loss | $ (1,616) | $ (4,308)
Available for sale securities, 12 months or longer, number of investment positions | 318 | 332
Held to Maturity securities, 12 months or longer, number of investment positions | 138 | 141
Available for sale securities, 12 months or longer, fair value | $ 2,523,114 | $ 2,653,765
Held to Maturity securities, 12 months or longer, fair value | 533,147 | 530,005
Available for sale securities, 12 months or longer, unrealized loss | (194,657) | (238,759)
Held to Maturity securities, 12 months or longer, unrealized loss | $ (24,920) | $ (32,524)
Available for sale securities, total, number of investment positions | 337 | 354
Held to Maturity securities, total, number of investment positions | 169 | 188
Available for sale securities, total, fair value | $ 2,585,434 | $ 2,720,435
Held to Maturity securities, total, fair value | 709,197 | 797,617
Available for sale securities, total, unrealized loss | (195,167) | (239,451)
Held to Maturity securities, total, unrealized loss | $ (26,536) | $ (36,832)
Agency Residential MBS [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 10 | 12
Held to Maturity securities, less than 12 months, number of investment positions | 0 | 0
Available for sale securities, less than 12 months, fair value | $ 13,725 | $ 18,030
Held to Maturity securities, less than 12 months, fair value | 0 | 0
Available for sale securities, less than 12 months, unrealized loss | (420) | (471)
Held to Maturity securities, less than 12 months, unrealized loss | $ 0 | $ 0
Available for sale securities, 12 months or longer, number of investment positions | 102 | 103
Held to Maturity securities, 12 months or longer, number of investment positions | 76 | 80
Available for sale securities, 12 months or longer, fair value | $ 186,156 | $ 192,963
Held to Maturity securities, 12 months or longer, fair value | 49,121 | 52,771
Available for sale securities, 12 months or longer, unrealized loss | (14,067) | (17,520)
Held to Maturity securities, 12 months or longer, unrealized loss | $ (3,418) | $ (4,218)
Available for sale securities, total, number of investment positions | 112 | 115
Held to Maturity securities, total, number of investment positions | 76 | 80
Available for sale securities, total, fair value | $ 199,881 | $ 210,993
Held to Maturity securities, total, fair value | 49,121 | 52,771
Available for sale securities, total, unrealized loss | (14,487) | (17,991)
Held to Maturity securities, total, unrealized loss | $ (3,418) | $ (4,218)
US States and Political Subdivisions Debt Securities [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 4 | 2
Held to Maturity securities, less than 12 months, number of investment positions | 13 | 24
Available for sale securities, less than 12 months, fair value | $ 4,668 | $ 2,764
Held to Maturity securities, less than 12 months, fair value | 8,648 | 15,822
Available for sale securities, less than 12 months, unrealized loss | (17) | (21)
Held to Maturity securities, less than 12 months, unrealized loss | $ (19) | $ (78)
Available for sale securities, 12 months or longer, number of investment positions | 39 | 40
Held to Maturity securities, 12 months or longer, number of investment positions | 27 | 26
Available for sale securities, 12 months or longer, fair value | $ 49,171 | $ 51,759
Held to Maturity securities, 12 months or longer, fair value | 24,879 | 25,814
Available for sale securities, 12 months or longer, unrealized loss | (1,586) | (1,680)
Held to Maturity securities, 12 months or longer, unrealized loss | $ (184) | $ (299)
Available for sale securities, total, number of investment positions | 43 | 42
Held to Maturity securities, total, number of investment positions | 40 | 50
Available for sale securities, total, fair value | $ 53,839 | $ 54,523
Held to Maturity securities, total, fair value | 33,527 | 41,636
Available for sale securities, total, unrealized loss | (1,603) | (1,701)
Held to Maturity securities, total, unrealized loss | $ (203) | $ (377)
Agency Commercial MBS [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 1 | 2
Available for sale securities, less than 12 months, fair value | $ 3,220 | $ 6,966
Available for sale securities, less than 12 months, unrealized loss | $ (6) | $ (132)
Available for sale securities, 12 months or longer, number of investment positions | 0 | 0
Available for sale securities, 12 months or longer, fair value | $ 0 | $ 0
Available for sale securities, 12 months or longer, unrealized loss | $ 0 | $ 0
Available for sale securities, total, number of investment positions | 1 | 2
Available for sale securities, total, fair value | $ 3,220 | $ 6,966
Available for sale securities, total, unrealized loss | $ (6) | $ (132)
Corporate Debt Securities [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 0 | 0
Held to Maturity securities, less than 12 months, number of investment positions | 18 | 23
Available for sale securities, less than 12 months, fair value | $ 0 | $ 0
Held to Maturity securities, less than 12 months, fair value | 167,402 | 251,790
Available for sale securities, less than 12 months, unrealized loss | 0 | 0
Held to Maturity securities, less than 12 months, unrealized loss | $ (1,597) | $ (4,230)
Available for sale securities, 12 months or longer, number of investment positions | 134 | 138
Held to Maturity securities, 12 months or longer, number of investment positions | 35 | 35
Available for sale securities, 12 months or longer, fair value | $ 1,802,791 | $ 1,824,327
Held to Maturity securities, 12 months or longer, fair value | 459,147 | 451,420
Available for sale securities, 12 months or longer, unrealized loss | (164,641) | (195,334)
Held to Maturity securities, 12 months or longer, unrealized loss | $ (21,318) | $ (28,007)
Available for sale securities, total, number of investment positions | 134 | 138
Held to Maturity securities, total, number of investment positions | 53 | 58
Available for sale securities, total, fair value | $ 1,802,791 | $ 1,824,327
Held to Maturity securities, total, fair value | 626,549 | 703,210
Available for sale securities, total, unrealized loss | (164,641) | (195,334)
Held to Maturity securities, total, unrealized loss | $ (22,915) | $ (32,237)
US Government Agencies Debt Securities [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 1 | 3
Available for sale securities, less than 12 months, fair value | $ 1,937 | $ 12,085
Available for sale securities, less than 12 months, unrealized loss | $ (1) | $ (53)
Available for sale securities, 12 months or longer, number of investment positions | 19 | 19
Available for sale securities, 12 months or longer, fair value | $ 282,994 | $ 275,467
Available for sale securities, 12 months or longer, unrealized loss | $ (12,105) | $ (19,032)
Available for sale securities, total, number of investment positions | 20 | 22
Available for sale securities, total, fair value | $ 284,931 | $ 287,552
Available for sale securities, total, unrealized loss | $ (12,106) | $ (19,085)
Collateralized Debt Obligations [Member] |  |
Available for sale securities, less than 12 months, number of investment positions | 3 | 3
Available for sale securities, less than 12 months, fair value | $ 38,770 | $ 26,825
Available for sale securities, less than 12 months, unrealized loss | $ (66) | $ (15)
Available for sale securities, 12 months or longer, number of investment positions | 24 | 32
Available for sale securities, 12 months or longer, fair value | $ 202,002 | $ 309,249
Available for sale securities, 12 months or longer, unrealized loss | $ (2,258) | $ (5,193)
Available for sale securities, total, number of investment positions | 27 | 35
Available for sale securities, total, fair value | $ 240,772 | $ 336,074
Available for sale securities, total, unrealized loss | $ (2,324) | $ (5,208)

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