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Note 8 - Loans and Related Allowance for Loan and Lease Losses (Details Textual) xbrli-pure in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loans and Leases Receivable, Deferred Income, Total	$ 1,400,000		$ 1,600,000
Financing Receivable, Troubled Debt Restructuring	$ 3,800,000		4,400,000
Number of Days Past Due	90 days
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 91,000		456,000
Allowance for Loan and Lease Losses, Write-offs	517,000	$ 13,000
Loans and Leases Receivable, Allowance, Ending Balance	$ 7,206,000	$ 7,551,000	7,428,000	$ 7,190,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	0
Commercial And Industrial [Member]
Allowance for Loan and Lease Losses, Write-offs	$ 347,000	$ 9,000
Loans and Leases Receivable, Allowance, Ending Balance	586,000	1,256,000	969,000	999,000
Real Estate Construction Porfolio Segment [Member]
Allowance for Loan and Lease Losses, Write-offs	0
Loans and Leases Receivable, Allowance, Ending Balance	748,000	$ 92,000	100,000	$ 313,000
Threshold For Loans Evaluated For Impairment [Member]
Loans and Leases Receivable, before Fees, Gross	500,000
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, before Allowance for Credit Loss, Total	125,000
Provision Fluctuation [Member] | Commercial And Industrial [Member]
Allowance for Loan and Lease Losses, Write-offs	336,000
Loans and Leases Receivable, Allowance, Ending Balance			358,000
Provision Fluctuation [Member] | Real Estate Construction Porfolio Segment [Member]
Allowance for Loan and Lease Losses, Adjustments, Other	$ 661,000
Provision Fluctuation [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Allowance, Ending Balance			$ 435,000

X

- Definition

The number of days past due.

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Amount of other addition (reduction) in allowance reserve for credit loss.

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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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Amount of financing receivable modified as troubled debt restructuring.

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Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

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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 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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