Note 3 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016
Loans	$ 760,341	$ 754,283	$ 754,261
Pass [Member]
Loans	720,115	707,965
Special Mention [Member]
Loans	14,122	19,530
Substandard [Member]
Loans	26,104	26,788
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	44,925	47,025	45,115
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	42,145	44,250
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	1,720	1,862
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	1,060	913
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	19,306	17,080	18,562
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	18,316	16,586
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	612	192
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	378	302
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	359,143	349,090	347,372
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	339,616	327,561
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	8,378	9,403
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	11,149	12,126
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	30,540	30,358	35,970
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	28,656	28,425
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	1,307	1,349
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	577	584
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	9,367	11,830	9,849
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	9,167	11,630
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Special Mention [Member]
Loans	0
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Substandard [Member]
Loans	200	200
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	195,282	195,580	195,679
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	182,896	178,618
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	1,004	5,659
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	11,382	11,303
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	64,870	66,877	66,285
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	62,990	65,075
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	920	839
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	960	963
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	19,188	19,695	19,661
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	18,609	19,072
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	181	226
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	398	397
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	17,720	16,748	$ 15,768
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	17,720	16,748
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans	0
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans