Note 16 - Income Taxes - Reconciliation Between U.S. Federal Statutory Rate and Effective Rate (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statutory federal income tax rate	21.00%	21.00%	35.00%
State tax expense, net of federal benefit	5.50%	5.50%	4.80%
Impact of rate change on deferred taxes	0.00%	0.00%	(4.90%)
Permanent items, including nondeductible expenses	(0.10%)	(1.40%)	0.10%
State investment tax credit	(0.10%)	(0.20%)	(0.70%)
Federal, state and foreign research and development credits	(1.40%)	(3.40%)	(1.40%)
Foreign rate differential	(0.20%)	(0.40%)	0.50%
Domestic production deduction	0.00%	0.00%	(2.80%)
Stock compensation	0.60%	(4.80%)	(0.20%)
Non-deductible Section 162(m) compensation limitation	0.30%	4.30%	0.70%
Foreign derived intangible income deduction	(0.90%)	(1.30%)	0.00%
Effective income tax rate	24.70%	19.30%	31.10%