Note 5 - Qualified Affordable Housing Partnership Investments (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Proportional Amortization Method Qualified Affordable Housing Project Investments	$ 3,391		$ 3,529
Proportional Amortization Method Qualified Affordable Housing Project Investments Unfunded Liability Obligation	$ 330		$ 361
Qualified Affordable Housing Project Investments Term	18 years
Proportional Amortization Method Qualified Affordable Housing Project Investments Amortization	$ 138	$ 171
Minimum [Member]
Qualified Affordable Housing Project Investments Return Rate	3.00%
Maximum [Member]
Qualified Affordable Housing Project Investments Return Rate	6.00%