Note 13 - Income Taxes - Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
U.S. federal statutory rate in effect	21.00%	35.00%	35.00%
State and local taxes, net of federal benefit	4.60%	3.60%	11.80%
Sec. 199 manufacturing deduction		(3.80%)	(33.60%)
Meals and entertainment	0.60%	1.80%	64.30%
Tax credits	(0.60%)	(1.30%)	(48.70%)
Change in valuation allowance		0.60%	205.40%
Change in U.S. federal statutory rate		(37.70%)
Change in tax affect of SERP		(11.40%)
All other, net	1.10%	(2.80%)	122.40%
Effective income tax rate	26.70%	(16.00%)	356.60%