Note 3 - Loans Receivable and Related Allowance for Loan Losses - Nonaccrual Loans by Aging Category (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Nonaccrual	$ 2,587	$ 2,237
Residential Portfolio Segment [Member]
Nonaccrual	955	855
Home Equity Loans and Lines of Credit [Member]
Nonaccrual	428	487
Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	907	606
Commercial Portfolio Segment [Member]
Nonaccrual	215	174
Consumer Portfolio Segment [Member]
Nonaccrual	82	115
Not Past Due [Member]
Nonaccrual	277	452
Not Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	245	335
Not Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	4	6
Not Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	28	111
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	309	265
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	309	265
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	278	113
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	72	74
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	31
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	175	39
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	1,723	1,407
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Nonaccrual	638	446
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Home Equity Loans and Lines of Credit [Member]
Nonaccrual	424	481
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member]
Nonaccrual	539	230
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Nonaccrual	40	135
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Nonaccrual	$ 82	$ 115