Note 6 - Allowance for Loan Losses and Impaired Loans (Details Textual)	12 Months Ended
	Dec. 31, 2019 USD ($)		Dec. 31, 2018 USD ($)	Dec. 31, 2015 USD ($)
Provision for Loan and Lease Losses, Total	$ 655,000		$ 325,000
Loans and Leases Receivable, Gross, Total	570,353,000		536,465,000
Impaired Financing Receivable, Recorded Investment, Total	7,761,000		10,298,000
Impaired Financing Receivable, with No Related Allowance, Recorded Investment	4,149,000		3,369,000
Financing Receivable, Troubled Debt Restructuring	4,800,000		7,300,000
Financing Receivable, Troubled Debt Restructuring, Collectively Evaluated for impairment	3,600,000		4,700,000
Financing Receivable, Troubled Debt Restructuring, Related Allowance	174,000		259,000
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	$ 4,800,000		$ 7,300,000
Financing Receivable, Modifications, Number of Contracts	3		3
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts		[1]	0
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Ending Balance			$ 0
Purchase Credit Impaired Loans			0
Additional Funds Advanced Loans [Member]
Financing Receivable, Number of Loans	2
Maximum [Member]
Financing Receivable, Troubled Debt Restructuring				$ 250,000
Collateral Pledged [Member]
Impaired Financing Receivable, Recorded Investment, Total	$ 2,900,000		2,800,000
Doubtful [Member]
Loans and Leases Receivable, Gross, Total	0		0
Unlikely to be Collected Financing Receivable [Member]
Loans and Leases Receivable, Gross, Total	0		0
Unallocated Financing Receivables [Member]
Provision for Loan and Lease Losses, Total	$ 0		$ 0

[1] Loans past due 30 days or more are considered to be in default.