Note 3 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Loans	$ 766,796	$ 765,284	$ 775,566
Pass [Member]
Loans	730,204	728,741
Special Mention [Member]
Loans	15,807	14,611
Substandard [Member]
Loans	20,785	21,932
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	45,029	48,122	44,883
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	43,619	46,469
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	755	825
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	655	828
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	20,037	16,443	21,810
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	19,255	15,868
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	438	175
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	344	400
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	352,063	351,172	355,801
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	338,114	338,776
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	7,591	7,663
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	6,358	4,733
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	48,909	45,214	35,151
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	47,606	41,282
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	618	578
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	685	3,354
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	11,541	8,583	9,230
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	11,541	8,583
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Special Mention [Member]
Loans	0	0
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Substandard [Member]
Loans
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	187,591	194,049	200,572
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	172,844	177,963
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	4,318	4,865
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	10,429	11,221
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	67,867	67,768	70,194
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	63,869	66,335
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	2,039	444
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	1,959	989
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	18,746	18,956	19,134
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	18,350	18,496
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	41	53
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	355	407
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	15,013	14,977	$ 18,791
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	15,006	14,969
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans	7	8
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans