Note 3 - Loans - Age Analysis of Past Due Loans and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Accruing loans past due	$ 6,218	$ 4,469
Nonaccrual loans	8,176	12,350
Current loans	761,172	737,464
Loans	775,566	754,283	$ 764,209
Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	6,218	4,469
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Accruing loans past due	615	420
Nonaccrual loans	608	635
Current loans	43,660	45,970
Loans	44,883	47,025	47,934
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	615	420
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Accruing loans past due	202	33
Nonaccrual loans	348	209
Current loans	21,260	16,838
Loans	21,810	17,080	24,307
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	202	33
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Commercial [Member]
Accruing loans past due	1,233	492
Nonaccrual loans	3,079	6,360
Current loans	351,489	342,238
Loans	355,801	349,090	345,181
Real Estate Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	1,233	492
Real Estate Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Accruing loans past due	792	54
Nonaccrual loans	102	190
Current loans	34,257	30,114
Loans	35,151	30,358	32,292
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	792	54
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Accruing loans past due
Nonaccrual loans	199
Current loans	9,031	11,830
Loans	9,230	11,830	9,141
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Residential [Member]
Accruing loans past due	2,984	3,179
Nonaccrual loans	3,013	3,944
Current loans	194,575	188,457
Loans	200,572	195,580	196,140
Real Estate Portfolio Segment [Member] | Residential [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	2,984	3,179
Real Estate Portfolio Segment [Member] | Residential [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Real Estate Portfolio Segment [Member] | Farmland [Member]
Accruing loans past due	187	95
Nonaccrual loans	678	800
Current loans	69,329	65,982
Loans	70,194	66,877	70,137
Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	187	95
Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Accruing loans past due	205	196
Nonaccrual loans	149	212
Current loans	18,780	19,287
Loans	19,134	19,695	19,936
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	205	196
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due
Consumer and Other Portfolio Segment [Member] | Other [Member]
Accruing loans past due
Nonaccrual loans
Current loans	18,791	16,748
Loans	18,791	16,748	$ 19,141
Consumer and Other Portfolio Segment [Member] | Other [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due
Consumer and Other Portfolio Segment [Member] | Other [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due