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Note 4 - Securities - Investment Securities Continuous Unrealized Loss Position (Details) - USD ($) $ in Thousands | Sep. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Debt securities available for sale, less than twelve months, gross unrealized losses | $ 935 | $ 1,758
Debt securities available for sale, less than twelve months, fair value | 21,887 | 276,720
Debt Securities Available for Sale, Twelve Months or More, Gross Unrealized Losses | 12,805 | 44,570
Debt Securities, Available for Sale, Twelve Months or More, Fair Value | 206,625 | 472,739
Debt Securities, Available for Sale, Gross Unrealized Losses | 13,739 | 46,328
Debt Securities, Available for Sale, Fair Value | 228,512 | 749,459
Debt securities held to maturity, less than twelve months, gross unrealized losses | 53 | 536
Debt securities held to maturity, less than twelve months, fair value | 3,077 | 40,115
Debt securities held to maturity, more than twelve months, gross unrealized losses | 49,179 | 74,835
Debt securities held to maturity, more than twelve months, fair value | 575,759 | 593,233
Debt securities held to maturity, gross unrealized losses | 49,232 | 75,371
Debt securities held to maturity, fair value | 578,835 | 633,348
Total | (49,232) | (75,371)
Collateralized Mortgage-Backed Securities [Member] |  |
Debt securities available for sale, less than twelve months, gross unrealized losses | (0) | 6
Debt securities available for sale, less than twelve months, fair value | 0 | 577
Debt Securities Available for Sale, Twelve Months or More, Gross Unrealized Losses | 990 | 24,204
Debt Securities, Available for Sale, Twelve Months or More, Fair Value | 25,182 | 179,178
Debt Securities, Available for Sale, Gross Unrealized Losses | 990 | 24,210
Debt Securities, Available for Sale, Fair Value | 25,182 | 179,755
Debt securities held to maturity, less than twelve months, gross unrealized losses | (0) | 536
Debt securities held to maturity, less than twelve months, fair value | 146 | 40,115
Debt securities held to maturity, more than twelve months, gross unrealized losses | 37,440 | 54,614
Debt securities held to maturity, more than twelve months, fair value | 333,063 | 356,215
Debt securities held to maturity, gross unrealized losses | 37,440 | 55,150
Debt securities held to maturity, fair value | 333,209 | 396,330
Total | (37,440) | (55,150)
US States and Political Subdivisions Debt Securities [Member] |  |
Debt securities available for sale, less than twelve months, gross unrealized losses | (0) | (0)
Debt securities available for sale, less than twelve months, fair value | 0 | 0
Debt Securities Available for Sale, Twelve Months or More, Gross Unrealized Losses | 630 | 1,000
Debt Securities, Available for Sale, Twelve Months or More, Fair Value | 9,290 | 9,072
Debt Securities, Available for Sale, Gross Unrealized Losses | 630 | 1,000
Debt Securities, Available for Sale, Fair Value | 9,290 | 9,072
Debt securities held to maturity, less than twelve months, gross unrealized losses | 53 | (0)
Debt securities held to maturity, less than twelve months, fair value | 2,931 | 0
Debt securities held to maturity, more than twelve months, gross unrealized losses | 304 | 589
Debt securities held to maturity, more than twelve months, fair value | 4,565 | 7,247
Debt securities held to maturity, gross unrealized losses | 357 | 589
Debt securities held to maturity, fair value | 7,496 | 7,247
Total | (357) | (589)
Corporate Debt Securities [Member] |  |
Debt securities available for sale, less than twelve months, gross unrealized losses | 935 | 1,307
Debt securities available for sale, less than twelve months, fair value | 21,887 | 25,596
Debt Securities Available for Sale, Twelve Months or More, Gross Unrealized Losses | 11,185 | 19,366
Debt Securities, Available for Sale, Twelve Months or More, Fair Value | 172,153 | 284,489
Debt Securities, Available for Sale, Gross Unrealized Losses | 12,119 | 20,673
Debt Securities, Available for Sale, Fair Value | 194,040 | 310,085
US Treasury Securities [Member] |  |
Debt securities available for sale, less than twelve months, gross unrealized losses |  | 445
Debt securities available for sale, less than twelve months, fair value |  | 250,547
Debt Securities Available for Sale, Twelve Months or More, Gross Unrealized Losses |  | (0)
Debt Securities, Available for Sale, Twelve Months or More, Fair Value |  | 0
Debt Securities, Available for Sale, Gross Unrealized Losses |  | 445
Debt Securities, Available for Sale, Fair Value |  | 250,547
Debt securities held to maturity, less than twelve months, gross unrealized losses | (0) | (0)
Debt securities held to maturity, less than twelve months, fair value | 0 | 0
Debt securities held to maturity, more than twelve months, gross unrealized losses | 11,435 | 19,632
Debt securities held to maturity, more than twelve months, fair value | 238,131 | 229,771
Debt securities held to maturity, gross unrealized losses | 11,435 | 19,632
Debt securities held to maturity, fair value | 238,130 | 229,771
Total | $ (11,435) | $ (19,632)

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