Note 3 - Loans Receivable - Past Due and Non-accrual Status of Loans (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016
Loans, past due	$ 3,713,000	$ 1,926,000
Loans, current	431,097,000	417,065,000
Loans	434,810,000	418,991,000
Loans, nonaccrual loans	700,000	924,000
Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans, past due	173,000
Loans, current	12,105,000	10,204,000
Loans	12,278,000	10,204,000
Loans, nonaccrual loans
Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member]
Loans, past due	299,000
Loans, current	33,616,000	27,480,000
Loans	33,915,000	27,480,000
Loans, nonaccrual loans
Real Estate Portfolio Segment [Member] | Residential [Member]
Loans, past due	1,370,000	1,442,000
Loans, current	115,744,000	110,184,000
Loans	117,114,000	111,626,000
Loans, nonaccrual loans	459,000	577,000
Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans, past due	894,000	115,000
Loans, current	172,819,000	172,133,000
Loans	173,713,000	172,248,000
Loans, nonaccrual loans	211,000	336,000
Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans, past due	619,000	93,000
Loans, current	60,533,000	59,716,000
Loans	61,152,000	59,809,000
Loans, nonaccrual loans	27,000	11,000
Equity Lines Portfolio Segment [Member]
Loans, past due	297,000	258,000
Loans, current	28,617,000	29,698,000
Loans	28,914,000	29,956,000
Loans, nonaccrual loans
Consumer Portfolio Segment [Member]
Loans, past due	61,000	18,000
Loans, current	7,663,000	7,650,000
Loans	7,724,000	7,668,000
Loans, nonaccrual loans	3,000
Financing Receivables, 30 to 59 Days Past Due [Member]
Loans, past due	1,883,000	1,113,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans, past due	173,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member]
Loans, past due	172,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Residential [Member]
Loans, past due	578,000	672,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans, past due	364,000	115,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans, past due	496,000	60,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Equity Lines Portfolio Segment [Member]
Loans, past due	93,000	258,000
Financing Receivables, 30 to 59 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans, past due	7,000	8,000
Financing Receivables, 60 to 89 Days Past Due [Member]
Loans, past due	806,000	232,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans, past due
Financing Receivables, 60 to 89 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member]
Loans, past due	95,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Residential [Member]
Loans, past due	648,000	193,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans, past due
Financing Receivables, 60 to 89 Days Past Due [Member] | Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans, past due	23,000	33,000
Financing Receivables, 60 to 89 Days Past Due [Member] | Equity Lines Portfolio Segment [Member]
Loans, past due
Financing Receivables, 60 to 89 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans, past due	40,000	6,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans, past due	1,024,000	581,000
Loans, nonaccrual loans	19
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Residential [Member]
Loans, past due
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Construction Loan Portfolio Segment [Member] | Land Acquisition Development And Commercial [Member]
Loans, past due	32,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Residential [Member]
Loans, past due	144,000	577,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans, past due	530,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Commercial Industrial and Agricultural Portfolio Segment [Member]
Loans, past due	100,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Equity Lines Portfolio Segment [Member]
Loans, past due	204,000
Financing Receivables, Equal to Greater than 90 Days Past Due [Member] | Consumer Portfolio Segment [Member]
Loans, past due	$ 14,000	$ 4,000