Note 9 - Allowance for Loan Losses and Credit Quality Information (Details Textual)	3 Months Ended
Mar. 31, 2018 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Loans and Leases Receivable, Nonperforming, Nonaccrual of Interest	$ 3,264,000		$ 3,144,000
Impaired Financing Receivable, Related Allowance	948,000		1,073,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Provision for Loan Losses	0
Loan Receivable for Which Value of Collateral Sufficient to Repay	700,000		400,000
Financing Receivable, Modifications, Recorded Investment	2,575,000		3,044,000
Loans and Leases Receivable, Impaired, Troubled Debt, Interest Income	$ 600,000
Loan to Value Ration	75.00%
Loans and Leases Receivable, Impaired, Commitment to Lend			800,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0
Allowance for Credit Losses, Change in Method of Calculating Impairment	$ 800,000		$ 900,000
Percentage Reserves For Loan Losses On Troubled Debt Restructurings	8.70%		9.80%
Loans and Leases Receivable, Allowance, Ending Balance	$ 9,129,000	$ 9,590,000	$ 9,311,000	$ 9,903,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	400,000
Provision for Loan and Lease Losses, Total	(125,000)	(270,000)
Acquired Loans [Member]
Provision for Loan and Lease Losses, Total	0
Nonperforming Financial Instruments [Member]
Impaired Financing Receivable, Related Allowance	800,000		900,000
Financing Receivable, Modifications, Recorded Investment	1,804,000		1,915,000
Nonperforming Financial Instruments [Member] \| Classified [Member]
Financing Receivable, Modifications, Recorded Investment	1,300,000	500,000
Performing Financial Instruments [Member]
Financing Receivable, Modifications, Recorded Investment	771,000		$ 1,129,000
Performing Financial Instruments [Member] \| Classified [Member]
Financing Receivable, Modifications, Recorded Investment	$ 100,000	$ 45,000

Loan receivable for which value of collateral sufficient to repay.

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- Definition

Represents the loan to value ratio.

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- Definition

Percentage reserves for loan losses on troubled debt restructurings.

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Amount of allowance for credit losses related to receivables which had been measured under a general allowance for credit losses methodology that are now identified as troubled debt restructurings.

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The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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- Definition

Amount of expense related to loan loss not accounted for as debt securities, with evidence of deterioration of credit quality.

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The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

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- Definition

Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default.

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Amount of allowance for credit losses related to recorded investment.

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- Definition

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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- Definition

Reflects the unfunded portion of contractual agreements to lend funds to borrowers for loans whose terms have been modified by troubled debt restructuring.

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Reflects the carrying amount of loans deemed to be questionable as to collection on which no interest is continuing to be recognized.

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The gross interest income that would have been recorded in the period on troubled debt restructurings, if the loans had been current in accordance with their original terms and had been outstanding throughout the period or since origination, if held for part of the period.

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

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