Note 4 - Qualified Affordable Housing Project Investment (Details Textual)	3 Months Ended	6 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)
Affordable Housing Tax Credits and Other Tax Benefits, Amount	$ 98,000	$ 196,000
Income Tax Expense (Benefit) [Member]
Amortization Method Qualified Affordable Housing Project Investments, Amortization	82,000	164,000
Other Assets [Member]
Amortization Method Qualified Affordable Housing Project Investments	3,800,000	3,800,000
Other Liabilities [Member]
Qualified Affordable Housing Project Investments, Commitment	$ 3,300,000	$ 3,300,000