Note 5 - Loans (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	$ 2,800	$ 2,900
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	226	353	$ 228
Impaired Financing Receivable, Recorded Investment	$ 13,147	$ 18,794
Percentage of Collateral Coverage to Loan Balance to Consider Restructured Loan to Performing and Accrual Status	100.00%
Financing Receivable, Modifications, Number of Contracts	1	8	13
Loans and Leases Receivable, Impaired, Commitment to Lend	$ 33	$ 0
Financing Receivable, Modifications, Recorded Investment	$ 10,900	$ 12,100
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	116
Troubled Debt Restructurings Percentage of Gross Portfolio Loans	1.24%	1.50%
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	0
Doubtful Grade Remaining Outstanding Period, Minimum	180 days
Mortgage Loans in Process of Foreclosure, Amount	$ 530
Loans and Leases Receivable, Allowance	$ 11,925	$ 11,544
Percentage of Allowance for Loan and Lease Losses out of Net Loans	1.36%	1.44%
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Asset	$ 227,700	$ 229,400
Reserve for Unfunded Commitments Included in Other Liabilities	$ 695	$ 695
Percentage of Loan Portfolio Secured by Real Estate	77.00%
Percentage of Unallocated Allowance Amount out of Allowance for Loan and Lease Losses	3.00%	4.00%
Maximum Loan to Value, Percentage	80.00%
Commercial Portfolio Segment [Member]
Impaired Financing Receivable, Recorded Investment	$ 3,154	$ 3,525
Financing Receivable, Modifications, Number of Contracts		4	2
Commercial Portfolio Segment [Member] \| Line of Credit [Member]
Financing Receivable, Modifications, Number of Contracts	1
Performing Financial Instruments [Member]
Impaired Financing Receivable, Recorded Investment	$ 7,300	$ 7,100
Financing Receivable, Number of Contracts Qualified as Troubled Debt Restructuring	110

Period that a loan classified as Doubtful will remain outstanding.

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Number of financing receivables that qualified as troubled debt restructurings.

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The maximum loan to value percentage.

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Percentage of the allowance for loan and lease losses as a percentage of total gross loans.

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The percentage of collateral coverage to loan balance, to consider restructured loan to performing and accrual status.

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The percentage of the gross loan portfolio that is secured by real estate.

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The percentage of unallocated allowance amount out of allowance for loan and lease losses.

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Amount of the reserve for unfunded commitments.

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No definition available.

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Percentage of gross portfolio loans that are classified as loans modified under a troubled debt restructuring.

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No definition available.

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The fair value of financial assets, which are not recognized in the financial statements (off-balance sheet) because they fail to meet some other criterion for recognition.

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Number of financing receivables that have been modified by troubled debt restructurings.

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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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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 investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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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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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 amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

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Recorded investment of consumer mortgage loan receivables secured by residential real estate properties for which formal foreclosure proceedings are in process.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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