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Note 3 - Debt Securities Available for Sale and Held to Maturity – Schedule of Estimated Market Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Investment securities available for sale, amortized cost, 1 year or less	$ 168,382	$ 124,667
Investment securities available for sale, fair value, 1 year or less	167,424	124,448
Investment securities held to maturity, amortized cost, 1 year or less	29,562	13,508
Investment securities held to maturity, fair value, 1 year or less	29,535	13,468
Investment securities available for sale, amortized cost, over 1 to 5 years	1,234,938	993,874
Investment securities available for sale, fair value, over 1 to 5 years	1,183,538	940,578
Investment securities held to maturity, amortized cost, over 1 to 5 years	411,838	347,566
Investment securities held to maturity, fair value, over 1 to 5 years	413,990	342,500
Investment securities available for sale, amortized cost, over 5 to 10 years	879,304	1,292,627
Investment securities available for sale, fair value, over 5 to 10 years	803,645	1,130,169
Investment securities held to maturity, amortized cost, over 5 to 10 years	338,673	425,634
Investment securities held to maturity, fair value, over 5 to 10 years	329,770	398,138
Investment securities available for sale, amortized cost, subtotal	2,282,624	2,411,168
Investment securities available for sale, fair value, subtotal	2,154,607	2,195,195
Investment securities held to maturity, amortized cost, subtotal	780,073	786,708
Investment securities held to maturity, fair value, subtotal	773,295	754,106
Debt securities available for sale, amortized cost	3,447,173	3,634,471
Debt securities available for sale	3,305,324	3,395,810
Debt securities held to maturity, amortized cost	826,506	844,635
Deb Securities, Held-to-maturity, Excluding Accrued Interest, Fair Value	817,188	807,838
Collateralized Debt Obligations [Member]
Debt securities available for sale, amortized cost, without single date maturity	562,034	987,155
Debt securities available for sale, without single date maturity	561,063	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	562,034	987,155
Debt securities available for sale	561,063	982,589
Agency Residential MBS [Member]
Debt securities available for sale, amortized cost, without single date maturity	203,929	229,050
Debt securities available for sale, without single date maturity	192,490	211,060
Debt securities held to maturity, amortized cost, without single date maturity	46,433	57,927
Debt securities held to maturity, fair value, without single date maturity	43,893	53,732
Debt securities available for sale, amortized cost	203,929	229,050
Debt securities available for sale	192,490	211,060
Debt securities held to maturity, amortized cost	46,433	57,927
Deb Securities, Held-to-maturity, Excluding Accrued Interest, Fair Value	43,893	53,732
Agency Commercial MBS [Member]
Debt securities available for sale, amortized cost, without single date maturity	398,586	7,098
Debt securities available for sale, without single date maturity	397,164	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	398,586	7,098
Debt securities available for sale	$ 397,164	$ 6,966

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