Note 4 - Qualified Affordable Housing Project Investment (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Amortization Method Qualified Affordable Housing Project Investments, Amortization	$ 89,000	$ 96,000
Affordable Housing Tax Credits and Other Tax Benefits, Amount	106,000	$ 111,000
Other Assets [Member]
Investments, Total	2,800,000		$ 2,900,000
Other Liabilities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 496,000		$ 496,000