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Note 3 - Investment Securities - Amortized Cost and Estimated Market Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands | Jun. 30, 2025 | Dec. 31, 2024
--- | --- | ---
Investment securities available for sale, amortized cost, 1 year or less | $ 126,847 | $ 124,667
Investment securities available for sale, fair value, 1 year or less | 126,010 | 124,448
Investment securities held to maturity, amortized cost, 1 year or less | 26,288 | 13,508
Investment securities held to maturity, fair value, 1 year or less | 26,218 | 13,468
Investment securities available for sale, amortized cost, over 1 to 5 years | 1,207,932 | 993,874
Investment securities available for sale, fair value, over 1 to 5 years | 1,150,997 | 940,578
Investment securities held to maturity, amortized cost, over 1 to 5 years | 400,042 | 347,566
Investment securities held to maturity, fair value, over 1 to 5 years | 399,891 | 342,500
Investment securities available for sale, amortized cost, over 5 to 10 years | 971,204 | 1,292,627
Investment securities available for sale, fair value, over 5 to 10 years | 877,752 | 1,130,169
Investment securities held to maturity, amortized cost, over 5 to 10 years | 358,232 | 425,634
Investment securities held to maturity, fair value, over 5 to 10 years | 344,596 | 398,138
Investment securities available for sale, amortized cost, subtotal | 2,305,983 | 2,411,168
Investment securities available for sale, fair value, subtotal | 2,154,759 | 2,195,195
Investment securities held to maturity, amortized cost, subtotal | 784,562 | 786,708
Investment securities held to maturity, fair value, subtotal | 770,705 | 754,106
Debt securities available for sale, amortized cost | 3,392,197 | 3,634,471
Debt securities available for sale | 3,226,449 | 3,395,810
Debt securities held to maturity, amortized cost | 834,440 | 844,635
Deb Securities, Held-to-maturity, Excluding Accrued Interest, Fair Value | 817,719 | 807,838
Collateralized Debt Obligations [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 782,050 | 987,155
Debt securities available for sale, without single date maturity | 780,147 | 982,589
Debt securities held to maturity, amortized cost, without single date maturity | 0 | 0
Debt securities held to maturity, fair value, without single date maturity | 0 | 0
Debt securities available for sale, amortized cost | 782,050 | 987,155
Debt securities available for sale | 780,147 | 982,589
Agency Residential MBS [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 208,198 | 229,050
Debt securities available for sale, without single date maturity | 195,278 | 211,060
Debt securities held to maturity, amortized cost, without single date maturity | 49,878 | 57,927
Debt securities held to maturity, fair value, without single date maturity | 47,014 | 53,732
Debt securities available for sale, amortized cost | 208,198 | 229,050
Debt securities available for sale | 195,278 | 211,060
Debt securities held to maturity, amortized cost | 49,878 | 57,927
Deb Securities, Held-to-maturity, Excluding Accrued Interest, Fair Value | 47,014 | 53,732
Agency Commercial MBS [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 95,966 | 7,098
Debt securities available for sale, without single date maturity | 96,265 | 6,966
Debt securities held to maturity, amortized cost, without single date maturity | 0 | 0
Debt securities held to maturity, fair value, without single date maturity | 0 | 0
Debt securities available for sale, amortized cost | 95,966 | 7,098
Debt securities available for sale | $ 96,265 | $ 6,966

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