Note 4 - Loans and the Allowance for Loan Losses - Loan Portfolio Allocated by Management's Internal Risk Ratings (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Pass [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	$ 41,074	$ 35,508
Pass [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	48,715	39,426
Pass [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	211,813	185,739
Pass [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	18,171	15,048
Pass [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	22,819	25,220
Pass [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	41,408	37,983
Pass [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	384,000	338,924
Watch [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	491	883
Watch [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	289	387
Watch [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	1,271	2,442
Watch [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans		247
Watch [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans		149
Watch [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans
Watch [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	2,051	4,108
Substandard [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	377	693
Substandard [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	42	43
Substandard [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	2,082	3,914
Substandard [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	781	893
Substandard [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	168	105
Substandard [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	335	344
Substandard [Member] | Commercial and Residential Portfolio Segments [Member]
Loans	3,785	5,992
Doubtful [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans
Doubtful [Member] | Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans
Doubtful [Member] | Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans
Doubtful [Member] | Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans
Doubtful [Member] | Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans
Doubtful [Member] | Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans
Doubtful [Member] | Commercial and Residential Portfolio Segments [Member]
Loans
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Loans	41,942	37,084
Commercial Portfolio Segment [Member] | Agricultural Loans [Member]
Loans	49,046	39,856
Commercial Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	215,166	192,095
Commercial Portfolio Segment [Member] | Construction Loans [Member]
Loans	18,952	16,188
Residential Portfolio Segment [Member] | Real Estate Loan [Member]
Loans	22,987	25,474
Residential Portfolio Segment [Member] | Equity Lines of Credit [Member]
Loans	41,743	38,327
Commercial and Residential Portfolio Segments [Member]
Loans	389,836	349,024
Loans	$ 446,913	$ 400,971