Note 9 - Investments - Held-to-Maturity by Credit Rating (Details) - USD ($) $ in Thousands	Sep. 30, 2026	Dec. 31, 2025
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	$ 277,577	$ 290,811
US States and Political Subdivisions Debt Securities, Excluding Prerefunded and Escrowed to Maturity [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	169,279	171,075
US States and Political Subdivisions Debt Securities, Excluding Prerefunded and Escrowed to Maturity [Member] \| Moody's, Aaa Rating [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	60,869	59,367
US States and Political Subdivisions Debt Securities, Excluding Prerefunded and Escrowed to Maturity [Member] \| Moody's, Aa1 Rating [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	105,027	110,255
US States and Political Subdivisions Debt Securities, Excluding Prerefunded and Escrowed to Maturity [Member] \| Moody's, A2 Rating [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	2,435	523
US States and Political Subdivisions Debt Securities, Excluding Prerefunded and Escrowed to Maturity [Member] \| Not Rated [Member]
Debt Securities, Held-to-Maturity, Excluding Accrued Interest, after Allowance for Credit Loss	$ 948	$ 930

- Definition

Amount excluding accrued interest, after allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity).

+ References + Details