Note 3 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Loans	$ 770,046	$ 754,283	$ 776,117
Pass [Member]
Loans	731,121	707,965
Special Mention [Member]
Loans	12,907	19,530
Substandard [Member]
Loans	26,018	26,788
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	45,363	47,025	45,773
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	43,641	44,250
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	838	1,862
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	884	913
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	25,246	17,080	26,547
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	24,759	16,586
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	164	192
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	323	302
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	346,251	349,090	349,392
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	332,075	327,561
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	4,744	9,403
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	9,432	12,126
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	36,533	30,358	33,724
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	32,100	28,425
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	1,206	1,349
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	3,227	584
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	8,905	11,830	10,325
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	8,707	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	198	200
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	196,332	195,580	195,045
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	180,695	178,618
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	4,921	5,659
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	10,716	11,303
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	71,903	66,877	73,801
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	70,111	65,075
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	923	839
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	869	963
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	18,677	19,695	20,378
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	18,206	19,072
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	102	226
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	369	397
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	20,836	16,748	$ 21,132
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	20,827	16,748
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans	9
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans