Note 9 - Allowance for Loan Losses and Credit Quality Information - Aging of Past Due Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Loans past due	$ 2,965	$ 1,707
Current loans	588,890	559,087
Loans receivable	591,855	560,794
Loans 90 days or more past due and still accruing	0	0
Residential Portfolio Segment [Member]
Loans past due	1,398	679
Current loans	105,914	102,576
Loans receivable	107,312	103,255
Loans 90 days or more past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member]
Loans receivable	329,251	299,080
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	471	0
Current loans	175,314	153,343
Loans receivable	175,785	153,343
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	0	0
Current loans	153,466	145,737
Loans receivable	153,466	145,737
Loans 90 days or more past due and still accruing	0	0
Consumer Portfolio Segment [Member]
Loans past due	868	669
Current loans	74,116	72,614
Loans receivable	74,984	73,283
Loans 90 days or more past due and still accruing	0	0
Commercial Portfolio Segment [Member]
Loans receivable	80,308	85,176
Commercial Portfolio Segment [Member] | Transportation Industry Loans [Member]
Loans past due	0	0
Current loans	9,418	10,509
Loans receivable	9,418	10,509
Loans 90 days or more past due and still accruing	0	0
Commercial Portfolio Segment [Member] | Commercial Business Other [Member]
Loans past due	228	359
Current loans	70,662	74,308
Loans receivable	70,890	74,667
Loans 90 days or more past due and still accruing	0	0
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans past due	1,475	839
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	833	342
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	212	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	318	412
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Transportation Industry Loans [Member]
Loans past due	0	0
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Business Other [Member]
Loans past due	112	85
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	881	275
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	457	158
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	424	117
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Transportation Industry Loans [Member]
Loans past due	0	0
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Business Other [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due	609	593
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	108	179
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	259	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans past due	126	140
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Transportation Industry Loans [Member]
Loans past due	0	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Portfolio Segment [Member] | Commercial Business Other [Member]
Loans past due	$ 116	$ 274