Note 3 - Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Nonaccrual	$ 3,523	$ 2,587
Residential Portfolio Segment [Member]
Nonaccrual	1,619	955
Home Equity Loans and Lines of Credit [Member]
Nonaccrual	75	428
Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	1,613	907
Commercial Portfolio Segment [Member]
Nonaccrual	168	215
Consumer Portfolio Segment [Member]
Nonaccrual	48	82
Not Past Due [Member]
Nonaccrual	1,408	277
Not Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	220	245
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	1,016	28
Not Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	168
Not Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member]
Nonaccrual	70	309
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	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		309
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	278
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual		72
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	31
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual		175
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	2,021	1,723
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	1,329	638
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	71	424
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	573	539
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual		40
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	$ 48	$ 82