Note 4 - Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Nonaccrual	$ 2,586	$ 2,587
Residential Portfolio Segment [Member]
Nonaccrual	808	955
Home Equity Loans and Lines of Credit [Member]
Nonaccrual	351	428
Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	1,042	907
Commercial Portfolio Segment [Member]
Nonaccrual	263	215
Consumer Portfolio Segment [Member]
Nonaccrual	122	82
Not Past Due [Member]
Nonaccrual	376	277
Not Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	239	245
Not Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	3	4
Not Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	134	28
Not Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual
Not Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, 30 to 59 Days Past Due [Member]
Nonaccrual	291	309
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual
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	250	309
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	41
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual
Financial Asset, 60 to 89 Days Past Due [Member]
Nonaccrual	230	278
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	71	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	159	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	1,689	1,723
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	498	638
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	348	424
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	499	539
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	222	40
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	$ 122	$ 82