Note 4 - Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Nonaccrual	$ 2,852	$ 3,523
Residential Portfolio Segment [Member]
Nonaccrual	1,251	1,619
Home Equity Loans and Lines of Credit [Member]
Nonaccrual	132	75
Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	1,312	1,613
Commercial Portfolio Segment [Member]
Nonaccrual	141	168
Consumer Portfolio Segment [Member]
Nonaccrual	16	48
Not Past Due [Member]
Nonaccrual	1,202	1,408
Not Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	208	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	849	1,016
Not Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	141	168
Not Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, 30 to 59 Days Past Due [Member]
Nonaccrual	20	70
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	0	70
Financial Asset, 30 to 59 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	0	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	20	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, 60 to 89 Days Past Due [Member]
Nonaccrual	129	24
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	69	0
Financial Asset, 60 to 89 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	60	24
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Nonaccrual	1,501	2,021
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	974	1,329
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	128	71
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	383	573
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	$ 16	$ 48