Note 16 - Income Tax (Benefit) Provision - Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Amount computed using the statutory rate	21.00%	21.00%	35.00%
Section 199 manufacturing deduction			(0.50%)
Small Agri-biodiesel Producer Tax Credit	(3.00%)	(1.60%)
Federal BTC benefit	(23.40%)	(12.90%)
State BTC benefit	(5.80%)	(3.30%)
Credit for increasing research activities	(0.20%)	(0.20%)	(0.80%)
Dividends received deduction	(0.40%)	(0.60%)	(5.20%)
State income taxes, net	4.00%	4.20%	2.80%
State research credits	(0.90%)
State rate change impact	(1.60%)
Tax expense recorded as an increase in unrecognized tax benefit		5.30%	1.10%
Tax Cuts and Jobs Act of 2017 impact			(72.50%)
Other	(0.20%)	(0.20%)	(1.10%)
Effective Income Tax Rate Reconciliation, Percent, Total	(10.50%)	11.70%	(41.20%)