Note 11 - Fair Value Measurements and Fair Values of Financial Instruments - Additional Quantitative Information About Assets Measured at Fair Value on a Nonrecurring Basis (Details) - Appraisal of Collateral [Member] - Fair Value, Inputs, Level 3 [Member] - Meaurement Input, Appraisal Adjustments Rate [Member] $ in Thousands	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Impaired loans, fair value	$ 321	$ 319
Other real estate owned, fair value	$ 389	$ 1,824
Minimum [Member] | Impaired Loans [Member]
Unobservable input, range	0	0
Minimum [Member] | Other Real Estate Owned [Member]
Unobservable input, range	0	0
Maximum [Member] | Impaired Loans [Member]
Unobservable input, range	0	0.03
Maximum [Member] | Other Real Estate Owned [Member]
Unobservable input, range	0.12	0.12
Weighted Average [Member] | Impaired Loans [Member]
Unobservable input, range	0	0.01
Weighted Average [Member] | Other Real Estate Owned [Member]
Unobservable input, range	0.12	0.12