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Note 4 - Loans and Related Allowance for Loan and Lease Losses (Details Textual)	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loans and Leases Receivable, Deferred Income	$ 1,500,000	$ 1,700,000
Financing Receivable, Modifications, Recorded Investment	5,400,000	6,700,000
Financing Receivable, Allowance for Credit Losses, Write-downs	$ 509,000	436,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0
Number of Days Past Due	90 years
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 437,000	309,000	$ 259,000
Provision for Loan, Lease, and Other Losses	1,045,000	$ 570,000	$ 315,000
Threshold For Loans Evaluated For Impairment [Member]
Loans and Leases Receivable, before Fees, Gross	1,000,000
Threshold For Loans Evaluated For Impairment [Member] | Outside Consultant [Member]
Loans and Leases Receivable, before Fees, Gross	250,000
Threshold For Loans Evaluated For Impairment [Member] | Criticized Relationships [Member]
Financing Receivable, Gross	125,000
Residential Loan [Member] | Real Estate Mortgage Portfolio Segment [Member]
Financing Receivable, Modifications, Subsequent Default, Number of Contracts		4
Provision for Loan, Lease, and Other Losses	$ (1,182,000)	$ (48,000)

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The number of days past due.

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Amount of direct write-downs of financing receivables charged against the allowance.

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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, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount of deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements.

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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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Amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date. Such amount may include accrued interest receivable in accordance with the terms of the note. The note also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. Excludes amounts related to receivables held-for-sale.

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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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