Note 4 - Allowance for Loan Losses - Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Allowance for loan losses, beginning balance	$ 3,758	$ 3,636	$ 3,636
Allowance for loan losses, charge- offs	(148)		(1,078)
Allowance for loan losses, recoveries	13		58
Allowance for loan losses, provisions	237	70	1,142
Allowance for loan losses, ending balance	3,860		3,758
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	3,860		3,758
Loans	455,590		444,195
Loans: individually evaluated for impairment	5,352		5,317
Loans: collectively evaluated for impairment	450,238		438,878
Construction Loan Portfolio Segment [Member] \| Residential [Member]
Allowance for loan losses, beginning balance	94	63	63
Allowance for loan losses, charge- offs
Allowance for loan losses, recoveries
Allowance for loan losses, provisions	26		31
Allowance for loan losses, ending balance	120		94
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	120		94
Loans	19,452		15,221
Loans: individually evaluated for impairment
Loans: collectively evaluated for impairment	19,452		15,221
Construction Loan Portfolio Segment [Member] \| Land Acquisition Development And Commercial [Member]
Allowance for loan losses, beginning balance	311	173	173
Allowance for loan losses, charge- offs	(3)		(150)
Allowance for loan losses, recoveries
Allowance for loan losses, provisions	(8)		288
Allowance for loan losses, ending balance	300		311
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	300		311
Loans	38,348		35,601
Loans: individually evaluated for impairment	181		181
Loans: collectively evaluated for impairment	38,167		35,420
Real Estate Portfolio Segment [Member] \| Residential [Member]
Allowance for loan losses, beginning balance	955	866	866
Allowance for loan losses, charge- offs	(103)		(293)
Allowance for loan losses, recoveries	9
Allowance for loan losses, provisions	153		382
Allowance for loan losses, ending balance	1,014		955
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	1,014		955
Loans	129,505		121,649
Loans: individually evaluated for impairment	427		360
Loans: collectively evaluated for impairment	129,078		121,289
Real Estate Portfolio Segment [Member] \| Commercial [Member]
Allowance for loan losses, beginning balance	1,603	1,516	1,516
Allowance for loan losses, charge- offs			(454)
Allowance for loan losses, recoveries			43
Allowance for loan losses, provisions	(75)		498
Allowance for loan losses, ending balance	1,528		1,603
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	1,528		1,603
Loans	173,803		173,999
Loans: individually evaluated for impairment	4,435		4,098
Loans: collectively evaluated for impairment	169,368		169,901
Commercial Industrial and Agricultural Portfolio Segment [Member]
Allowance for loan losses, beginning balance	441	461	461
Allowance for loan losses, charge- offs			(80)
Allowance for loan losses, recoveries
Allowance for loan losses, provisions	1		60
Allowance for loan losses, ending balance	442		441
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	442		441
Loans	58,327		61,197
Loans: individually evaluated for impairment	10		379
Loans: collectively evaluated for impairment	58,317		60,818
Equity Lines Portfolio Segment [Member]
Allowance for loan losses, beginning balance	237	338	338
Allowance for loan losses, charge- offs
Allowance for loan losses, recoveries
Allowance for loan losses, provisions	(19)		(101)
Allowance for loan losses, ending balance	218		237
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	218		237
Loans	28,973		28,835
Loans: individually evaluated for impairment	299		299
Loans: collectively evaluated for impairment	28,674		28,536
Consumer Portfolio Segment [Member]
Allowance for loan losses, beginning balance	108	97	97
Allowance for loan losses, charge- offs	(42)		(101)
Allowance for loan losses, recoveries	4		15
Allowance for loan losses, provisions	38		97
Allowance for loan losses, ending balance	108		108
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	108		108
Loans	7,182		7,693
Loans: individually evaluated for impairment
Loans: collectively evaluated for impairment	7,182		7,693
Unallocated Financing Receivables [Member]
Allowance for loan losses, beginning balance	9	$ 122	122
Allowance for loan losses, charge- offs
Allowance for loan losses, recoveries
Allowance for loan losses, provisions	121		(113)
Allowance for loan losses, ending balance	130		9
Allowance for loan losses: individually evaluated for impairment
Allowance for loan losses: collectively evaluated for impairment	130		9
Loans
Loans: individually evaluated for impairment
Loans: collectively evaluated for impairment

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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