Note 4 - Allowance for Loan Losses - Loans by Credit Quality Indicators (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Loans	$ 455,590	$ 444,195
Pass [Member]
Loans	438,809	428,225
Special Mention [Member]
Loans	14,316	12,964
Substandard [Member]
Loans	1,659	2,005
Substandard Nonaccrual [Member]
Loans	785	804
Doubtful [Member]
Loans	21	197
Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans	19,452	15,221
Construction Loan Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	19,452	15,221
Construction Loan Portfolio Segment [Member] | Residential [Member] | Special Mention [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	38,348	35,601
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Pass [Member]
Loans	34,195	31,433
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Special Mention [Member]
Loans	4,110	3,987
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member] | Substandard [Member]
Loans
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	129,505	121,649
Real Estate Portfolio Segment [Member] | Residential [Member] | Pass [Member]
Loans	128,584	120,575
Real Estate Portfolio Segment [Member] | Residential [Member] | Special Mention [Member]
Loans	494	342
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard [Member]
Loans	185	559
Real Estate Portfolio Segment [Member] | Residential [Member] | Substandard Nonaccrual [Member]
Loans	242
Real Estate Portfolio Segment [Member] | Residential [Member] | Doubtful [Member]
Loans		173
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	173,803	173,999
Real Estate Portfolio Segment [Member] | Commercial [Member] | Pass [Member]
Loans	164,348	165,760
Real Estate Portfolio Segment [Member] | Commercial [Member] | Special Mention [Member]
Loans	8,334	7,386
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard [Member]
Loans	636	644
Real Estate Portfolio Segment [Member] | Commercial [Member] | Substandard Nonaccrual [Member]
Loans	485	209
Real Estate Portfolio Segment [Member] | Commercial [Member] | Doubtful [Member]
Loans
Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans	58,327	61,197
Commercial Industrial and Agricultural Portfolio Segment [Member] | Pass [Member]
Loans	56,374	59,042
Commercial Industrial and Agricultural Portfolio Segment [Member] | Special Mention [Member]
Loans	1,378	1,249
Commercial Industrial and Agricultural Portfolio Segment [Member] | Substandard [Member]
Loans	539	503
Commercial Industrial and Agricultural Portfolio Segment [Member] | Substandard Nonaccrual [Member]
Loans	15	379
Commercial Industrial and Agricultural Portfolio Segment [Member] | Doubtful [Member]
Loans	21	24
Equity Lines Portfolio Segment [Member]
Loans	28,973	28,835
Equity Lines Portfolio Segment [Member] | Pass [Member]
Loans	28,674	28,536
Equity Lines Portfolio Segment [Member] | Special Mention [Member]
Loans
Equity Lines Portfolio Segment [Member] | Substandard [Member]
Loans	299	299
Equity Lines Portfolio Segment [Member] | Substandard Nonaccrual [Member]
Loans
Equity Lines Portfolio Segment [Member] | Doubtful [Member]
Loans
Consumer Portfolio Segment [Member]
Loans	7,182	7,693
Consumer Portfolio Segment [Member] | Pass [Member]
Loans	7,182	7,658
Consumer Portfolio Segment [Member] | Special Mention [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