Note 4 - Loans and the Allowance for Loan Losses (Details Textual) xbrli-pure in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Impaired Financing Receivable, Recorded Investment, Total	$ 2,247,000		$ 2,244,000
Impaired Financing Receivable, Related Allowance	154,000		154,000
Impaired Financing Receivable, with Related Allowance, Recorded Investment	538,000		539,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	1,709,000		1,705,000
Impaired Financing Receivable, Average Recorded Investment, Total	2,256,000	$ 1,352,000	1,777,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	15,000	18,000	62,000
Impaired Financing Receivable, Interest Income, Cash Basis Method, Total	0	$ 0
Financing Receivable, Troubled Debt Restructuring	1,012,000		1,016,000
Financing Receivable Modifications Related Allowances	33,000		33,000
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	$ 2,310,000		$ 2,050,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 33,000	$ 26,000
Number of Loans, 90 Days Past Due and Still Accruing	0		0
Deferred Loan Origination Costs	$ 496,000	$ 598,000