Note 6 - Investments in Affordable Housing and Alternative Energy Partnerships - Usage of Affordable Housing and Other Tax Credits Including Energy Tax Credit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Affordable housing and other tax credits recognized	$ 17,727	$ 13,422	$ 10,100
Alternative energy tax credit usage	$ 3,301	$ 24,472	$ 21,000