Note 4 - Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Nonaccrual	$ 3,012	$ 3,523
Residential Portfolio Segment [Member]
Nonaccrual	1,301	1,619
Home Equity Loans and Lines of Credit [Member]
Nonaccrual	74	75
Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	1,449	1,613
Commercial Portfolio Segment [Member]
Nonaccrual	146	168
Consumer Portfolio Segment [Member]
Nonaccrual	42	48
Not Past Due [Member]
Nonaccrual	1,240	1,408
Not Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	214	220
Not Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	4	4
Not Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	876	1,016
Not Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	146	168
Not Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member]
Nonaccrual	69	70
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	69	70
Financial Asset, 30 to 59 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, 60 to 89 Days Past Due [Member]
Nonaccrual		24
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual
Financial Asset, 60 to 89 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual		24
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Nonaccrual	1,703	2,021
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	1,018	1,329
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	70	71
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	573	573
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	$ 42	$ 48