Note 4 - Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Accruing loans not past due	$ 788,714	$ 802,158
Nonaccrual	3,012	3,523
Loans	795,188	809,918
Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,333	2,962
Nonaccrual	69	70
Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	507	696
Nonaccrual		24
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	622	579
Nonaccrual	1,703	2,021
Residential Portfolio Segment [Member]
Accruing loans not past due	295,560	304,161
Nonaccrual	1,301	1,619
Loans	298,491	308,031
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	1,213	1,836
Nonaccrual	69	70
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	226	239
Nonaccrual
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	191	176
Nonaccrual	1,018	1,329
Home Equity Loans and Lines of Credit [Member]
Accruing loans not past due	82,810	86,093
Nonaccrual	74	75
Loans	83,523	87,088
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	241	446
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	247	328
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	151	146
Nonaccrual	70	71
Commercial Real Estate Portfolio Segment [Member]
Accruing loans not past due	282,799	283,373
Nonaccrual	1,449	1,613
Loans	285,133	285,625
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	844	580
Nonaccrual
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due		41
Nonaccrual		24
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	41	18
Nonaccrual	573	573
Commercial Portfolio Segment [Member]
Accruing loans not past due	84,553	88,614
Nonaccrual	146	168
Loans	84,953	89,139
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	15	72
Nonaccrual
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due		46
Nonaccrual
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	239	239
Nonaccrual
Consumer Portfolio Segment [Member]
Accruing loans not past due	42,992	39,917
Nonaccrual	42	48
Loans	43,088	40,035
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	20	28
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	34	42
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual	$ 42	$ 48