Note 5 - Qualified Affordable Housing Partnership Investments (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Qualified Affordable Housing Project Investments Term (Year)	23 years
Proportional Amortization Method Qualified Affordable Housing Project Investments	$ 3,389	$ 2,529
Proportional Amortization Method Qualified Affordable Housing Project Investments Unfunded Liability Obligation	1,338	338
Proportional Amortization Method Qualified Affordable Housing Project Investments Original Amount	8,954	$ 7,954
Boston Capital [Member]
Proportional Amortization Method Qualified Affordable Housing Project Investments	990
Proportional Amortization Method Qualified Affordable Housing Project Investments Unfunded Liability Obligation	1,000
Proportional Amortization Method Qualified Affordable Housing Project Investments Original Amount	$ 1,000
Minimum [Member]
Qualified Affordable Housing Project Investments Return Rate	2.00%
Maximum [Member]
Qualified Affordable Housing Project Investments Return Rate	6.00%