Note 4 - Loans Receivable and Related Allowance for Loan Losses - Classes of Loan Portfolio by Aging Categories (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Accruing loans not past due	$ 683,098		$ 701,016
Nonaccrual	4,670	$ 4,670	2,237
Loans	694,866		715,172
Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	5,387		9,516
Nonaccrual		526	265
Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	1,404		1,612
Nonaccrual		45	113
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	307		791
Nonaccrual		3,605	1,407
Residential Portfolio Segment [Member]
Accruing loans not past due	282,766		289,732
Nonaccrual	824	824	855
Loans	287,437		295,405
Residential Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,626		3,586
Nonaccrual		72
Residential Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	1,024		747
Nonaccrual			74
Residential Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due	197		485
Nonaccrual		437	446
Home Equity Loans and Lines of Credit [Member]
Accruing loans not past due	97,361		101,920
Nonaccrual	532	532	487
Loans	98,628		103,752
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	438		707
Nonaccrual
Home Equity Loans and Lines of Credit [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	187		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	110		287
Nonaccrual		528	481
Commercial Real Estate Portfolio Segment [Member]
Accruing loans not past due	222,078		232,865
Nonaccrual	3,193	3,193	606
Loans	227,569		238,734
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	2,172		5,013
Nonaccrual		454	265
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	126		231
Nonaccrual		45
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due			19
Nonaccrual		2,559	230
Commercial Portfolio Segment [Member]
Accruing loans not past due	69,653		65,538
Nonaccrual	40	40	174
Loans	69,834		66,009
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	76		50
Nonaccrual
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	65		247
Nonaccrual			39
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual			135
Consumer Portfolio Segment [Member]
Accruing loans not past due	11,240		10,961
Nonaccrual	81	81	115
Loans	11,398		11,272
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Accruing loans past due	75		160
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Accruing loans past due	2		36
Nonaccrual
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Accruing loans past due
Nonaccrual		$ 81	$ 115