Note 3 - Investment Securities - Activity in Allowance for Credit Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 198
Provision for credit loss expense	(18)	$ 15
Balance, ending	180	198
Accounting Standards Update 2016-13
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	183
Balance, ending		183
Municipal securities.
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	198
Provision for credit loss expense	(18)	16
Balance, ending	180	198
Municipal securities. | Accounting Standards Update 2016-13
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	182
Balance, ending		182
Other securities
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Provision for credit loss expense		(1)
Other securities | Accounting Standards Update 2016-13
Debt Securities, Held-to-maturity, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 1
Balance, ending		$ 1