Note 4 - Allowance for Loan Losses - Loans by Credit Quality Indicators (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Loans	$ 466,343	$ 444,195
Pass [Member]
Loans	460,498	428,225
Special Mention [Member]
Loans	2,677	12,964
Special Mention Nonaccrual [Member]
Loans	484
Substandard [Member]
Loans	1,714	2,005
Substandard Nonaccrual [Member]
Loans	915	804
Doubtful [Member]
Loans	55	197
Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans	19,062	15,221
Construction Loan Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	19,062	15,221
Construction Loan Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans
Construction Loan Portfolio Segment [Member] | Residential [Member] | Special Mention Nonaccrual [Member]
Loans
Construction Loan Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans
Construction Loan Portfolio Segment [Member] | Residential [Member] | Substandard Nonaccrual [Member]
Loans
Construction Loan Portfolio Segment [Member] | Residential [Member] | Doubtful [Member]
Loans
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member]
Loans	26,048	35,601
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Pass [Member]
Loans	25,465	31,433
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Special Mention [Member]
Loans		3,987
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Special Mention Nonaccrual [Member]
Loans	82
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Substandard [Member]
Loans	458
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Substandard Nonaccrual [Member]
Loans	43	181
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Doubtful [Member]
Loans
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	141,728	121,649
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	140,428	120,575
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	369	342
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention Nonaccrual [Member]
Loans	255
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	385	559
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard Nonaccrual [Member]
Loans	236
Real Estate Portfolio Segment [Member] | Residential [Member] | Doubtful [Member]
Loans	55	173
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	187,894	173,999
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	184,717	165,760
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	2,137	7,386
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention Nonaccrual [Member]
Loans
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	573	644
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard Nonaccrual [Member]
Loans	467	209
Real Estate Portfolio Segment [Member] | Commercial [Member] | Doubtful [Member]
Loans
Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans	54,933	61,197
Commercial Industrial and Agricultural Portfolio Segment [Member] | Pass [Member]
Loans	54,593	59,042
Commercial Industrial and Agricultural Portfolio Segment [Member] | Special Mention [Member]
Loans	171	1,249
Commercial Industrial and Agricultural Portfolio Segment [Member] | Special Mention Nonaccrual [Member]
Loans
Commercial Industrial and Agricultural Portfolio Segment [Member] | Substandard [Member]
Loans		503
Commercial Industrial and Agricultural Portfolio Segment [Member] | Substandard Nonaccrual [Member]
Loans	169	379
Commercial Industrial and Agricultural Portfolio Segment [Member] | Doubtful [Member]
Loans		24
Equity Lines Portfolio Segment [Member]
Loans	28,675	28,835
Equity Lines Portfolio Segment [Member] | Pass [Member]
Loans	28,230	28,536
Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Loans
Equity Lines Portfolio Segment [Member] | Special Mention Nonaccrual [Member]
Loans	147
Equity Lines Portfolio Segment [Member] | Substandard [Member]
Loans	298	299
Equity Lines Portfolio Segment [Member] | Substandard Nonaccrual [Member]
Loans
Equity Lines Portfolio Segment [Member] | Doubtful [Member]
Loans
Consumer Portfolio Segment [Member]
Loans	8,003	7,693
Consumer Portfolio Segment [Member] | Pass [Member]
Loans	8,003	7,658
Consumer Portfolio Segment [Member] | Special Mention [Member]
Loans
Consumer Portfolio Segment [Member] | Special Mention Nonaccrual [Member]
Loans
Consumer Portfolio Segment [Member] | Substandard [Member]
Loans
Consumer Portfolio Segment [Member] | Substandard Nonaccrual [Member]
Loans		35
Consumer Portfolio Segment [Member] | Doubtful [Member]
Loans