Note 8 - Fair Value Measurements (Details Textual)	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020
Provision for Loan and Lease Losses, Total	$ 75,000	$ 351,000
Number of Foreclosed Real Estate Properties	0	0	0
Impaired Loan [Member]
Provision for Loan and Lease Losses, Total	$ 9,000	$ 1,000
Foreclosed Real Estate [Member]
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate, Write-down or Reserve, Amount	$ 0	$ 0
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Minimum [Member]
Fair Value Inputs, Estimated Selling Costs	10.00%		10.00%
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Maximum [Member]
Fair Value Inputs, Estimated Selling Costs	57.00%		66.00%
Fair Value, Inputs, Level 3 [Member] | Impaired Loan [Member] | Weighted Average [Member]
Fair Value Inputs, Estimated Selling Costs	23.00%		27.00%