Note 3 - Loans - Loan Portfolio by Credit Quality Indicator (Details) - USD ($)	Sep. 30, 2016	Dec. 31, 2015	Sep. 30, 2015
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	$ 43,042,000	$ 44,274,000
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	1,867,000	1,927,000
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	864,000	1,581,000
Commercial and Agricultural Portfolio Segment [Member] | Commercial [Member]
Loans	45,773,000	47,782,000	$ 48,759,000
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Pass [Member]
Loans	25,990,000	18,970,000
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Special Mention [Member]
Loans	184,000	18,000
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member] | Substandard [Member]
Loans	373,000	205,000
Commercial and Agricultural Portfolio Segment [Member] | Agricultural [Member]
Loans	26,547,000	19,193,000	27,373,000
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	325,699,000	320,566,000
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	7,685,000	13,653,000
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	16,008,000	12,043,000
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	349,392,000	346,262,000	347,703,000
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Pass [Member]
Loans	32,191,000	36,516,000
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Special Mention [Member]
Loans	268,000	913,000
Real Estate Portfolio Segment [Member] | Commercial Construction [Member] | Substandard [Member]
Loans	1,265,000	2,678,000
Real Estate Portfolio Segment [Member] | Commercial Construction [Member]
Loans	33,724,000	40,107,000	43,589,000
Real Estate Portfolio Segment [Member] | Residential Construction [Member] | Pass [Member]
Loans	10,125,000	9,413,000
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	200,000	0
Real Estate Portfolio Segment [Member] | Residential Construction [Member]
Loans	10,325,000	9,413,000	10,465,000
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	176,480,000	177,054,000
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	7,012,000	8,546,000
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	11,553,000	11,402,000
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	195,045,000	197,002,000	195,800,000
Real Estate Portfolio Segment [Member] | Farmland [Member] | Pass [Member]
Loans	71,047,000	56,798,000
Real Estate Portfolio Segment [Member] | Farmland [Member] | Special Mention [Member]
Loans	1,641,000	930,000
Real Estate Portfolio Segment [Member] | Farmland [Member] | Substandard [Member]
Loans	1,113,000	4,052,000
Real Estate Portfolio Segment [Member] | Farmland [Member]
Loans	73,801,000	61,780,000	61,551,000
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Pass [Member]
Loans	19,703,000	20,038,000
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Special Mention [Member]
Loans	264,000	156,000
Consumer and Other Portfolio Segment [Member] | Consumer [Member] | Substandard [Member]
Loans	411,000	411,000
Consumer and Other Portfolio Segment [Member] | Consumer [Member]
Loans	20,378,000	20,605,000	20,958,000
Consumer and Other Portfolio Segment [Member] | Other [Member] | Pass [Member]
Loans	21,132,000	16,467,000
Consumer and Other Portfolio Segment [Member] | Other [Member] | Special Mention [Member]
Loans	0	0
Consumer and Other Portfolio Segment [Member] | Other [Member] | Substandard [Member]
Loans		25,000
Consumer and Other Portfolio Segment [Member] | Other [Member]
Loans	21,132,000	16,492,000	8,006,000
Pass [Member]
Loans	725,409,000	700,096,000
Special Mention [Member]
Loans	18,921,000	26,143,000
Substandard [Member]
Loans	31,787,000	32,397,000
Loans	$ 776,117,000	$ 758,636,000	$ 764,204,000