Note 9 - Allowance for Loan Losses and Credit Quality Information - Troubled Debt Restructurings (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Troubled debt restructurings	$ 1,266	$ 1,478
Performing Financial Instruments [Member]
Troubled debt restructurings	83	442
Nonperforming Financial Instruments [Member]
Troubled debt restructurings	1,183	1,036
Residential Portfolio Segment [Member]
Troubled debt restructurings	258	612
Residential Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	22	355
Residential Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	236	257
Commercial Real Estate Portfolio Segment [Member]
Troubled debt restructurings	359	211
Commercial Real Estate Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	0	0
Commercial Real Estate Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	359	211
Consumer Portfolio Segment [Member]
Troubled debt restructurings	639	630
Consumer Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	51	62
Consumer Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	588	568
Commercial Portfolio Segment [Member]
Troubled debt restructurings	10	25
Commercial Portfolio Segment [Member] | Performing Financial Instruments [Member]
Troubled debt restructurings	10	25
Commercial Portfolio Segment [Member] | Nonperforming Financial Instruments [Member]
Troubled debt restructurings	$ 0	$ 0