Note 3 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands		3 Months Ended		12 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Average recorded investment	[1]	$ 5,842	$ 4,956	$ 5,901
Interest income recognized		21	46	137
Investor Owned Residential Real Estate [Member] | Consumer Real Estate Portfolio Segment [Member]
Average recorded investment	[1]	190	194	192
Interest income recognized		3	3	13
Commercial Real Estate, Owner Occupied [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment	[1]	2,640	3,269	2,668
Interest income recognized		1	38	9
Commercial Real Estate Other [Member] | Commercial Real Estate Portfolio Segment [Member]
Average recorded investment	[1]	2,720	654	2,723
Interest income recognized		17	0	100
Commercial and Industrial [Member] | Commercial Non Real Estate Segment [Member]
Average recorded investment	[1]	292	838	317
Interest income recognized		$ 0	5	15
Automobile Loan [Member] | Consumer Non Real Estate Portfolio Segment [Member]
Average recorded investment	[1]		1	1
Interest income recognized			$ 0	$ 0

[1] Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.