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Note 4 - Investment Securities - Schedule of Debt Securities, Available-for-sale (Details) - USD ($) $ in Thousands | Sep. 30, 2024 | Dec. 31, 2023
--- | --- | ---
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | $ 466,003 | $ 486,736
Unrealized Gains, Available-for-sale | 4 | 5
Unrealized Losses, Available-for-sale | (83,123) | (98,023)
Allowance for Credit Losses, Available-for-sale | 0 | 0
Unrealized Gains, Held-to-maturity | 0 | 0
Unrealized Losses, Held-to-maturity | (32,188) | (41,111)
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest | 137 | 213
Debt Securities, Held-to-maturity, Fair Value | 249,862 | 258,617
Amortized Cost, Total investment securities | 831,172 | 884,482
Unrealized Gains, Total investment securities | 4 | 5
Unrealized Losses, Total investment securities | (115,311) | (139,134)
Allowance for Credit Losses, Total investment securities | 137 | 213
Fair Value, Total investment securities | 715,865 | 745,353
US Treasury Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 739 | 1,120
Unrealized Gains, Available-for-sale | 2 | 4
Unrealized Losses, Available-for-sale | (2) | (3)
Allowance for Credit Losses, Available-for-sale | 0 | 0
Residential Mortgage-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 414,388 | 435,594
Unrealized Gains, Available-for-sale | 2 | 1
Unrealized Losses, Available-for-sale | (74,529) | (88,547)
Allowance for Credit Losses, Available-for-sale | 0 | 0
Unrealized Gains, Held-to-maturity | 0 | 0
Unrealized Losses, Held-to-maturity | (23,064) | (28,498)
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest | 56 | 99
Debt Securities, Held-to-maturity, Fair Value | 136,269 | 141,627
Commercial Mortgage-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 1,401 | 1,353
Unrealized Gains, Available-for-sale | 0 | 0
Unrealized Losses, Available-for-sale | (59) | (123)
Allowance for Credit Losses, Available-for-sale | 0 | 0
Asset-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 20 | 25
Unrealized Gains, Available-for-sale | 0 | 0
Unrealized Losses, Available-for-sale | 0 | (1)
Allowance for Credit Losses, Available-for-sale | 0 | 0
Corporate Bond Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 49,455 | 48,644
Unrealized Gains, Available-for-sale | 0 | 0
Unrealized Losses, Available-for-sale | (8,533) | (9,349)
Allowance for Credit Losses, Available-for-sale | 0 | 0
US States and Political Subdivisions Debt Securities [Member] |  |
Unrealized Gains, Held-to-maturity | 0 | 0
Unrealized Losses, Held-to-maturity | (9,124) | (12,613)
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Excluding Accrued Interest | 81 | 114
Debt Securities, Held-to-maturity, Fair Value | 113,593 | 116,990
Reported Value Measurement [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 549,122 | 584,754
Amortized Cost, Held-to-maturity | 282,050 | 299,728
Reported Value Measurement [Member] | US Treasury Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 739 | 1,119
Reported Value Measurement [Member] | Residential Mortgage-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 488,915 | 524,140
Amortized Cost, Held-to-maturity | 159,333 | 170,125
Reported Value Measurement [Member] | Commercial Mortgage-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 1,460 | 1,476
Reported Value Measurement [Member] | Asset-Backed Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 20 | 26
Reported Value Measurement [Member] | Corporate Bond Securities [Member] |  |
Available-for-sale, at fair value (amortized cost of $549,122 and $584,754, respectively) | 57,988 | 57,993
Reported Value Measurement [Member] | US States and Political Subdivisions Debt Securities [Member] |  |
Amortized Cost, Held-to-maturity | $ 122,717 | $ 129,603

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