Note 7 - Fair Value Measurements and Fair Value of Financial Instruments - Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024
Obligations of U.S. states and political subdivisions	$ 1,227,200	$ 612,847
Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	1,227,200	612,847
Equity securities	19,707	20,092
Derivatives - interest rate contracts	23,900	37,398
Total assets	1,270,807	670,337
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	128	171
Equity securities	9,920	9,739
Derivatives - interest rate contracts	0	0
Total assets	10,048	9,910
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Obligations of U.S. states and political subdivisions	1,220,493	606,150
Equity securities	9,787	10,353
Derivatives - interest rate contracts	23,900	37,398
Total assets	1,254,180	653,901
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Obligations of U.S. states and political subdivisions	6,579	6,526
Equity securities	0	0
Derivatives - interest rate contracts	0	0
Total assets	6,579	6,526
US Government Agencies Debt Securities [Member]
Obligations of U.S. states and political subdivisions	359,417	84,670
US Government Agencies Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	359,417	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	359,417	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	628,139	378,838
Residential Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	628,139	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	628,139	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	26,572	20,892
Commercial Mortgage-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	26,572	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	26,572	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	207,126	122,404
US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	207,126	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	200,547	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	6,579	6,526
Corporate Debt Securities [Member]
Obligations of U.S. states and political subdivisions	4,995	4,987
Corporate Debt Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	4,995	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	4,995	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	823	885
Asset-Backed Securities [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	823	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	823	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	128	171
Other Debt Obligations [Member] \| Fair Value, Recurring [Member]
Obligations of U.S. states and political subdivisions	128	171
Other Debt Obligations [Member] \| Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Obligations of U.S. states and political subdivisions	128	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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