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Note 3 - Investment Securities - Amortized Cost and Estimated Market Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands | Mar. 31, 2025 | Dec. 31, 2024
--- | --- | ---
Investment securities available for sale, amortized cost, 1 year or less | $ 83,272 | $ 124,667
Investment securities available for sale, fair value, 1 year or less | 82,874 | 124,448
Investment securities held to maturity, amortized cost, 1 year or less | 18,877 | 13,508
Investment securities held to maturity, fair value, 1 year or less | 18,819 | 13,468
Investment securities available for sale, amortized cost, over 1 to 5 years | 1,093,030 | 993,874
Investment securities available for sale, fair value, over 1 to 5 years | 1,039,910 | 940,578
Investment securities held to maturity, amortized cost, over 1 to 5 years | 379,408 | 347,566
Investment securities held to maturity, fair value, over 1 to 5 years | 376,571 | 342,500
Investment securities available for sale, amortized cost, over 5 to 10 years | 1,165,116 | 1,292,627
Investment securities available for sale, fair value, over 5 to 10 years | 1,040,310 | 1,130,169
Investment securities held to maturity, amortized cost, over 5 to 10 years | 387,536 | 425,634
Investment securities held to maturity, fair value, over 5 to 10 years | 367,602 | 398,138
Investment securities available for sale, amortized cost, subtotal | 2,341,418 | 2,411,168
Investment securities available for sale, fair value, subtotal | 2,163,094 | 2,195,195
Investment securities held to maturity, amortized cost, subtotal | 785,821 | 786,708
Investment securities held to maturity, fair value, subtotal | 762,992 | 754,106
Debt securities available for sale, amortized cost | 3,430,221 | 3,634,471
Debt securities available for sale | 3,236,049 | 3,395,810
Debt securities held to maturity, amortized cost | 839,349 | 844,635
Debt securities held to maturity, fair value | 813,125 | 807,838
Collateralized Debt Obligations [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 823,921 | 987,155
Debt securities available for sale, without single date maturity | 822,111 | 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 | 823,921 | 987,155
Debt securities available for sale | 822,111 | 982,589
Agency Residential MBS [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 218,825 | 229,050
Debt securities available for sale, without single date maturity | 204,342 | 211,060
Debt securities held to maturity, amortized cost, without single date maturity | 53,528 | 57,927
Debt securities held to maturity, fair value, without single date maturity | 50,133 | 53,732
Debt securities available for sale, amortized cost | 218,825 | 229,050
Debt securities available for sale | 204,342 | 211,060
Debt securities held to maturity, amortized cost | 53,528 | 57,927
Debt securities held to maturity, fair value | 50,133 | 53,732
Agency Commercial MBS [Member] |  |
Debt securities available for sale, amortized cost, without single date maturity | 46,057 | 7,098
Debt securities available for sale, without single date maturity | 46,502 | 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 | 46,057 | 7,098
Debt securities available for sale | $ 46,502 | $ 6,966

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