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Note 8 - Loans and Related Allowance for Loan and Lease Losses (Details Textual)	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loans and Leases Receivable, Deferred Income, Total	$ 1,300,000		$ 1,300,000
Financing Receivable, Troubled Debt Restructuring	3,600,000		1,300,000
Financing Receivable, Allowance for Credit Loss, Writeoff	$ 70,000		33,000
Number of Days Past Due (Day)	90 days
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 100,000		342,000
Provision for Loan and Lease Losses, Total	2,740,000	$ 240,000
Allowance for Loan and Lease Losses, Write-offs	508,000	517,000
Loans and Leases Receivable, Allowance, Ending Balance	$ 9,244,000	$ 7,206,000	6,768,000	$ 7,428,000
Financing Receivable, Modifications, Number of Contracts		0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	0
Commercial And Industrial [Member]
Provision for Loan and Lease Losses, Total	$ 212,000	$ (52,000)
Allowance for Loan and Lease Losses, Write-offs	61,000	347,000
Loans and Leases Receivable, Allowance, Ending Balance	$ 716,000	586,000	456,000	969,000
Financing Receivable, Modifications, Number of Contracts	1
Construction and Other [Member]
Provision for Loan and Lease Losses, Total	$ 134,000	625,000
Allowance for Loan and Lease Losses, Write-offs
Loans and Leases Receivable, Allowance, Ending Balance	254,000	748,000	$ 103,000	$ 100,000
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	150,000
Provision Fluctuation [Member]
Provision for Loan and Lease Losses, Total	1,800,000
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] | Construction and Other [Member]
Allowance for Loan and Lease Losses, Period Increase (Decrease), Total		661,000
Provision Fluctuation [Member] | Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Allowance, Ending Balance		$ 435,000
Increase in Specific Reserve [Member]
Provision for Loan and Lease Losses, Total	$ 510,000

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