Note 4 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Loans	$ 779,991	$ 782,027	$ 768,497
Pass [Member]
Loans	741,005	741,083
Special Mention [Member]
Loans	16,364	18,156
Substandard [Member]
Loans	22,622	22,788
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	51,368	57,410	46,693
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	49,378	55,808
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	1,277	729
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	713	873
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	15,290	16,799	16,351
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	13,554	15,664
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	1,215	637
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	521	498
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	373,263	373,534	354,098
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	357,401	358,139
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	7,681	7,662
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	8,181	7,733
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	44,305	47,849	49,659
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	43,876	47,087
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	128	45
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	301	717
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	14,947	12,500	8,145
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	14,947	12,500
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	181,004	187,714	193,376
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	166,641	170,050
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	4,147	7,107
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	10,216	10,557
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	64,056	62,709	67,111
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	59,805	58,713
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	1,825	1,912
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	2,426	2,084
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	17,907	18,485	18,805
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	17,555	18,104
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	91	59
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	261	322
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	17,851	5,027	$ 14,259
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	17,848	5,018
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans		5
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans	$ 3	$ 4