Note 9 - Allowance for Loan Losses and Credit Quality Information - Aging of Past Due Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loans past due	$ 2,054	$ 1,873
Current loans	605,590	592,983
Loans receivable	607,644	594,856
Loans 90 days or more past due and still accruing	0	0
Residential Portfolio Segment [Member]
Loans past due	889	1,082
Current loans	108,321	109,616
Loans receivable	109,210	110,698
Loans 90 days or more past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member]
Loans receivable	349,864	336,130
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	198	0
Current loans	198,181	195,564
Loans receivable	198,379	195,564
Loans 90 days or more past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	273	0
Current loans	151,212	140,566
Loans receivable	151,485	140,566
Loans 90 days or more past due and still accruing	0	0
Consumer Portfolio Segment [Member]
Loans past due	559	770
Current loans	72,526	71,762
Loans receivable	73,085	72,532
Loans 90 days or more past due and still accruing	0	0
Commercial Portfolio Segment [Member]
Loans past due	135	21
Current loans	75,350	75,475
Loans receivable	75,485	75,496
Loans 90 days or more past due and still accruing	0	0
Financial Asset, 30 to 59 Days Past Due [Member]
Loans past due	1,625	1,092
Financial Asset, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	798	680
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	198	0
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	273	0
Financial Asset, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	301	391
Financial Asset, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Loans past due	55	21
Financial Asset, 60 to 89 Days Past Due [Member]
Loans past due	180	425
Financial Asset, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	0	325
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	0	0
Financial Asset, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	180	100
Financial Asset, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Loans past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans past due	249	356
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	91	77
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	0	0
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	78	279
Financial Asset, Equal to or Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member]
Loans past due	$ 80	$ 0