Note 15 - Fair Values of Financial Instruments - Assets Measured at Fair Value on a Non-recurring Basis (Details) - Fair Value, Nonrecurring [Member] - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Other real estate owned	$ 9,000	$ 88,000
Total	407,000	88,000
Fair Value, Inputs, Level 1 [Member]
Other real estate owned
Total
Fair Value, Inputs, Level 2 [Member]
Other real estate owned
Total
Fair Value, Inputs, Level 3 [Member]
Other real estate owned	9,000	88,000
Total	407,000	$ 88,000
Commercial Portfolio Segment [Member]
Impaired loans	58,000
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member]
Impaired loans
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member]
Impaired loans
Commercial Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans	58,000
Commercial Real Estate Portfolio Segment [Member]
Impaired loans	340,000
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 1 [Member]
Impaired loans
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 2 [Member]
Impaired loans
Commercial Real Estate Portfolio Segment [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans	$ 340,000