Note 3 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017
Loans	$ 779,443	$ 765,284	$ 770,046
Pass [Member]
Loans	741,798	728,741
Special Mention [Member]
Loans	15,986	14,611
Substandard [Member]
Loans	21,659	21,932
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	47,292	48,122	45,363
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	45,612	46,469
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	847	825
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	833	828
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	21,415	16,443	25,246
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	20,026	15,868
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	919	175
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	470	400
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	349,408	351,172	346,251
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	335,844	338,776
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	7,000	7,663
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	6,564	4,733
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	53,570	45,214	36,533
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	52,181	41,282
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	631	578
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	758	3,354
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	12,897	8,583	8,905
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	12,897	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	189,153	194,049	196,332
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	173,987	177,963
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	4,543	4,865
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	10,623	11,221
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	70,069	67,768	71,903
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	66,002	66,335
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	2,002	444
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	2,065	989
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	18,623	18,956	18,677
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	18,239	18,496
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	38	53
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	346	407
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	17,016	14,977	$ 20,836
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	17,010	14,969
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans	6	8
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans