Note 3 - Loans - Age Analysis of Past Due Loans and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Accruing loans past due	$ 4,702	$ 4,469
Nonaccrual loans	11,249	12,350
Current loans	744,390	737,464
Loans	760,341	754,283	$ 754,261
Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	4,702	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	870	420
Nonaccrual loans	673	635
Current loans	43,382	45,970
Loans	44,925	47,025	45,115
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	870	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	184	33
Nonaccrual loans	206	209
Current loans	18,916	16,838
Loans	19,306	17,080	18,562
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	184	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	1,423	492
Nonaccrual loans	5,749	6,360
Current loans	351,971	342,238
Loans	359,143	349,090	347,372
Real Estate Portfolio Segment [Member] | Commercial [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	1,423	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	225	54
Nonaccrual loans	184	190
Current loans	30,131	30,114
Loans	30,540	30,358	35,970
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	225	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
Current loans	9,367	11,830
Loans	9,367	11,830	9,849
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	1,762	3,179
Nonaccrual loans	3,434	3,944
Current loans	190,086	188,457
Loans	195,282	195,580	195,679
Real Estate Portfolio Segment [Member] | Residential [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	1,762	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	92	95
Nonaccrual loans	800	800
Current loans	63,978	65,982
Loans	64,870	66,877	66,285
Real Estate Portfolio Segment [Member] | Farmland [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	92	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	144	196
Nonaccrual loans	203	212
Current loans	18,841	19,287
Loans	19,188	19,695	19,661
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	144	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	2
Nonaccrual loans
Current loans	17,718	16,748
Loans	17,720	16,748	$ 15,768
Consumer and Other Portfolio Segment [Member] | Other [Member] | Financing Receivables, 30-89 Days Past Due [Member]
Accruing loans past due	$ 2
Consumer and Other Portfolio Segment [Member] | Other [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Accruing loans past due