Note 4 - Loans and the Allowance for Credit Losses - Loan Modifications (Details) - Extended Maturity [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Modified	$ 7,512	$ 2,308	$ 8,877	$ 7,953
Real estate – commercial% of total segment financing receivables	0.50%	0.15%	0.59%	0.53%
Commercial Portfolio Segment [Member] \| Commercial Loans [Member]
Modified	$ 753		$ 1,580
Real estate – commercial% of total segment financing receivables	0.05%		0.11%
Commercial Portfolio Segment [Member] \| Agricultural Loans [Member]
Modified	$ 355	$ 2,232	$ 355	$ 7,105
Real estate – commercial% of total segment financing receivables	0.02%	1.45%	0.02%	4.60%
Commercial Portfolio Segment [Member] \| Real Estate Loan [Member]
Modified			$ 3,806
Real estate – commercial% of total segment financing receivables			0.25%
Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Modified	$ 3,136
Real estate – commercial% of total segment financing receivables	0.21%
Commercial Real Estate Portfolio Segment [Member] \| Commercial Loans [Member]
Modified		$ 76		$ 848
Real estate – commercial% of total segment financing receivables		0.01%		0.09%
Commercial Real Estate Portfolio Segment [Member] \| Real Estate Loan [Member]
Modified	$ 3,268
Real estate – commercial% of total segment financing receivables	0.22%
Commercial Real Estate Portfolio Segment [Member] \| Construction Loans [Member]
Modified			$ 3,136
Real estate – commercial% of total segment financing receivables			0.21%