Note 5 - Qualified Affordable Housing Partnership Investments (Details Textual) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Proportional Amortization Method Qualified Affordable Housing Project Investments	$ 3,252		$ 3,252		$ 3,529
Proportional Amortization Method Qualified Affordable Housing Project Investments Unfunded Liability Obligation	330		$ 330		$ 361
Qualified Affordable Housing Project Investments Term			18 years
Proportional Amortization Method Qualified Affordable Housing Project Investments Amortization	$ 138	$ 164	$ 277	$ 335
Minimum [Member]
Qualified Affordable Housing Project Investments Return Rate			3.00%
Maximum [Member]
Qualified Affordable Housing Project Investments Return Rate			6.00%