Note 3 - Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Accruing loans not past due	$ 802,158	$ 690,985
Nonaccrual	3,523	2,587
Loans	809,918	701,904
Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,962	5,481
Nonaccrual	70	309
Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	696	2,222
Nonaccrual	24	278
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	579	629
Nonaccrual	2,021	1,723
Residential Portfolio Segment [Member]
Accruing loans not past due	304,161	288,399
Nonaccrual	1,619	955
Loans	308,031	293,170
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	1,836	2,405
Nonaccrual	70
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	239	1,039
Nonaccrual		72
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	176	372
Nonaccrual	1,329	638
Home Equity Loans and Lines of Credit [Member]
Accruing loans not past due	86,093	95,908
Nonaccrual	75	428
Loans	87,088	97,541
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	446	626
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	328	553
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	146	26
Nonaccrual	71	424
Commercial Real Estate Portfolio Segment [Member]
Accruing loans not past due	283,373	226,133
Nonaccrual	1,613	907
Loans	285,625	229,951
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	580	2,141
Nonaccrual		309
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	41	543
Nonaccrual	24	31
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	18	227
Nonaccrual	573	539
Commercial Portfolio Segment [Member]
Accruing loans not past due	88,614	66,087
Nonaccrual	168	215
Loans	89,139	66,603
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	72	225
Nonaccrual
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	46	72
Nonaccrual		175
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	239	4
Nonaccrual		40
Consumer Portfolio Segment [Member]
Accruing loans not past due	39,917	14,458
Nonaccrual	48	82
Loans	40,035	14,639
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	28	84
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	42	15
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual	$ 48	$ 82