Note 4 - Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accruing loans not past due	$ 731,255	$ 690,985
Nonaccrual	2,586	2,587
Loans	741,950	701,904
Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	4,639	5,481
Nonaccrual	291	309
Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	2,990	2,222
Nonaccrual	230	278
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	480	629
Nonaccrual	1,689	1,723
Residential Portfolio Segment [Member]
Accruing loans not past due	290,062	288,399
Nonaccrual	808	955
Loans	294,361	293,170
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,050	2,405
Nonaccrual
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	1,379	1,039
Nonaccrual	71	72
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	62	372
Nonaccrual	498	638
Home Equity Loans and Lines of Credit [Member]
Accruing loans not past due	93,725	95,908
Nonaccrual	351	428
Loans	95,459	97,541
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	731	626
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	472	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	180	26
Nonaccrual	348	424
Commercial Real Estate Portfolio Segment [Member]
Accruing loans not past due	260,032	226,133
Nonaccrual	1,042	907
Loans	263,948	229,951
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	1,620	2,141
Nonaccrual	250	309
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	1,019	543
Nonaccrual	159	31
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	235	227
Nonaccrual	499	539
Commercial Portfolio Segment [Member]
Accruing loans not past due	68,571	66,087
Nonaccrual	263	215
Loans	69,077	66,603
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	172	225
Nonaccrual	41
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	68	72
Nonaccrual		175
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	3	4
Nonaccrual	222	40
Consumer Portfolio Segment [Member]
Accruing loans not past due	18,865	14,458
Nonaccrual	122	82
Loans	19,105	14,639
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	66	84
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	52	15
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual	$ 122	$ 82