Note 7 - Fair Value Measurements and Fair Value of Financial Instruments - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Obligations of U.S. states and political subdivisions	$ 1,252,202	$ 612,847
Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	1,252,202	612,847
Equity securities	20,133	20,092
Derivatives - interest rate contracts	19,505	37,398
Total assets	1,291,840	670,337
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	54	171
Equity securities	10,022	9,739
Derivatives - interest rate contracts	0	0
Total assets	10,076	9,910
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	1,245,576	606,150
Equity securities	10,111	10,353
Derivatives - interest rate contracts	19,505	37,398
Total assets	1,275,192	653,901
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	6,572	6,526
Equity securities	0	0
Derivatives - interest rate contracts	0	0
Total assets	6,572	6,526
US Government Agencies Debt Securities [Member]
Obligations of U.S. states and political subdivisions	399,128	84,670
US Government Agencies Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	399,128	84,670
US Government Agencies Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
US Government Agencies Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	399,128	84,670
US Government Agencies Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	0	0
Residential Mortgage-Backed Securities [Member]
Obligations of U.S. states and political subdivisions	607,899	378,838
Residential Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	607,899	378,838
Residential Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
Residential Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	607,899	378,838
Residential Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	0	0
Commercial Mortgage-Backed Securities [Member]
Obligations of U.S. states and political subdivisions	26,807	20,892
Commercial Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	26,807	20,892
Commercial Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
Commercial Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	26,807	20,892
Commercial Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	0	0
US States and Political Subdivisions Debt Securities [Member]
Obligations of U.S. states and political subdivisions	211,765	122,404
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	211,765	122,404
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	205,193	115,878
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	6,572	6,526
Corporate Debt Securities [Member]
Obligations of U.S. states and political subdivisions	5,999	4,987
Corporate Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	5,999	4,987
Corporate Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
Corporate Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	5,999	4,987
Corporate Debt Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	0	0
Asset-Backed Securities [Member]
Obligations of U.S. states and political subdivisions	550	885
Asset-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	550	885
Asset-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	0	0
Asset-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	550	885
Asset-Backed Securities [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	0	0
Other Debt Obligations [Member]
Obligations of U.S. states and political subdivisions	54	171
Other Debt Obligations [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	54	171
Other Debt Obligations [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	54	171
Other Debt Obligations [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	0	0
Other Debt Obligations [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	$ 0	$ 0

Fair value portion of asset recognized for present right to economic benefit.

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