Note 7 - Income Tax Expense - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statutory federal income tax rate	21.00%	21.00%	21.00%
State and local income taxes, net of federal income tax benefit	1.30%	4.80%	2.00%
Rate impacts due to foreign operations	(4.50%)	(3.90%)	(2.70%)
Changes in uncertain tax positions	0.20%	1.70%	0.40%
Compensation related	2.30%	(0.20%)	1.40%
R&D tax credits	(0.30%)	(0.90%)	(0.40%)
Other	0.30%	(1.40%)	(1.00%)
Effective income tax rate	20.30%	21.10%	20.70%