Note 5 - 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, 2020	Dec. 31, 2019	Dec. 31, 2018
Affordable housing and other tax credits recognized	$ 23,273	$ 21,523	$ 18,860
Alternative energy tax credit usage	$ 29,706	$ 17,786	$ 15,013