Note 14 - Income Taxes - Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.S. federal statutory rate in effect	21.00%	21.00%	35.00%
State and local taxes, net of federal benefit	3.70%	4.60%	3.60%
Sec. 199 manufacturing deduction			(3.80%)
Meals and entertainment	5.80%	0.60%	1.80%
Tax credits	(4.20%)	(0.60%)	(1.30%)
Change in valuation allowance			0.60%
Change in U.S. federal statutory rate			(37.70%)
Change in tax affect of SERP			(11.40%)
All other, net	0.80%	1.10%	(2.80%)
Effective income tax rate	27.10%	26.70%	(16.00%)