Note 9 - Allowance for Loan Losses and Credit Quality Information - Aging of Past Due Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Loans past due	$ 3,298	$ 1,707
Current Loans	596,524	559,087
Loans and leases receivable, gross carrying amount	599,822	560,794
Loans 90 days or more past due and still accruing	0	0
Residential Portfolio Segment [Member]
Loans past due	1,500	679
Current Loans	106,812	102,576
Loans and leases receivable, gross carrying amount	108,312	103,255
Loans 90 days or more past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member]
Loans and leases receivable, gross carrying amount	324,600	299,080
Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	471	0
Current Loans	175,452	153,343
Loans and leases receivable, gross carrying amount	175,923	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	148,677	145,737
Loans and leases receivable, gross carrying amount	148,677	145,737
Loans 90 days or more past due and still accruing	0	0
Consumer Portfolio Segment [Member]
Loans past due	563	669
Current Loans	73,997	72,614
Loans and leases receivable, gross carrying amount	74,560	73,283
Loans 90 days or more past due and still accruing	0	0
Commercial Portfolio Segment [Member]
Loans and leases receivable, gross carrying amount	92,350	85,176
Commercial Portfolio Segment [Member] | Transportation Industry Loans [Member]
Loans past due	0	0
Current Loans	9,872	10,509
Loans and leases receivable, gross carrying amount	9,872	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	764	359
Current Loans	81,714	74,308
Loans and leases receivable, gross carrying amount	82,478	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	2,034	839
Financing Receivables, 30 to 59 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	1,057	342
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Real Estate Portfolio Segment [Member] | Real Estate Loan [Member]
Loans past due	213	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	290	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	474	85
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans past due	737	275
Financing Receivables, 60 to 89 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	252	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	195	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	290	0
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans past due	527	593
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Residential Portfolio Segment [Member]
Loans past due	191	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	258	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	78	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	$ 0	$ 274