Note 4 - Loans and the Allowance for Loan 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 ($)
Impaired Financing Receivable, Recorded Investment, Total	$ 1,738,000		$ 1,275,000
Impaired Financing Receivable, Related Allowance	229,000		181,000
Impaired Financing Receivable, with Related Allowance, Recorded Investment	897,000		424,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	841,000		851,000
Impaired Financing Receivable, Average Recorded Investment, Total	1,352,000	$ 2,002,000	1,160,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	18,000	18,000	71,000
Impaired Financing Receivable, Interest Income, Cash Basis Method, Total	0	$ 0
Financing Receivable, Troubled Debt Restructuring	1,071,000		1,080,000
Financing Receivable Modifications Related Allowances	53,000		53,000
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	$ 0		0
Financing Receivable, Modifications, Number of Contracts	0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts	0	0
Financing Receivable, Nonaccrual	$ 1,457,000		$ 1,117,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 26,000	$ 15,000
Number of Loans, 90 Days Past Due and Still Accruing	0		0
Deferred Loan Origination Costs	$ 598,000	$ 498,000