Note 3 - Investment Securities - Activity in Allowance for Credit Losses HTM and AFS securities by major security (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 180	$ 180
Provision for credit loss expense		23
Balance, ending		203	$ 180
Balance, ending		989
Municipal securities.
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	180	180	198
Provision for credit loss expense		22	(18)
Balance, ending		202	$ 180
Corporate securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Provision for credit loss expense	$ 989	989
Balance, ending		989
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Provision for credit loss expense		1
Balance, ending		1
Balance, ending		$ 989