Note 5 - Allowance for Loan Losses (Details Textual)	Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)
Loan Balance For Reviewing High Risk Loans Minimum	$ 250,000	$ 250,000	$ 250,000
Impaired Financing Receivable, Number of Loans Below Review Threshold	123		139
Impaired Financing Receivable Recorded Investment Below Review Threshold	$ 3,500,000		$ 4,000,000
Loans and Leases Receivable, Gross, Total	958,723,000	782,027,000	779,443,000
Loans and Leases Receivable, Allowance, Ending Balance	6,600,000	$ 7,277,000	7,155,000	$ 7,508,000
Loans Not Classified as Impaired [Member] | Substandard [Member]
Loans and Leases Receivable, Gross, Total	5,930,000		8,730,000
Loans and Leases Receivable, Allowance, Ending Balance	$ 1,230,000		$ 1,250,000