Note 3 - Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Accruing loans not past due	$ 691,294	$ 701,016
Nonaccrual	2,587	2,237
Loans	701,904	715,172
Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	5,481	9,516
Nonaccrual	309	265
Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	2,222	1,612
Nonaccrual	278	113
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	320	791
Nonaccrual	1,723	1,407
Residential Portfolio Segment [Member]
Accruing loans not past due	288,462	289,732
Nonaccrual	955	855
Loans	293,170	295,405
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,405	3,586
Nonaccrual
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	1,039	747
Nonaccrual	72	74
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	309	485
Nonaccrual	638	446
Home Equity Loans and Lines of Credit [Member]
Accruing loans not past due	95,923	101,920
Nonaccrual	428	487
Loans	97,541	103,752
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	626	707
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	553	351
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	11	287
Nonaccrual	424	481
Commercial Real Estate Portfolio Segment [Member]
Accruing loans not past due	226,360	232,865
Nonaccrual	907	606
Loans	229,951	238,734
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,141	5,013
Nonaccrual	309	265
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	543	231
Nonaccrual	31
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due		19
Nonaccrual	539	230
Commercial Portfolio Segment [Member]
Accruing loans not past due	66,091	65,538
Nonaccrual	215	174
Loans	66,603	66,009
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	225	50
Nonaccrual
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	72	247
Nonaccrual	175	39
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual	40	135
Consumer Portfolio Segment [Member]
Accruing loans not past due	14,458	10,961
Nonaccrual	82	115
Loans	14,639	11,272
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	84	160
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	15	36
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual	$ 82	$ 115