Note 4 - Qualified Affordable Housing Project Investment (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Amortization Method Qualified Affordable Housing Project Investments, Amortization	$ 86,000	$ 87,000	$ 182,000	$ 169,000
Affordable Housing Tax Credits and Other Tax Benefits, Amount	109,000	$ 123,000	220,000	$ 248,000
Other Assets [Member]
Investments, Total	3,100,000		3,100,000		$ 3,200,000
Other Liabilities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments	$ 1,100,000		$ 1,100,000		$ 1,900,000