Note 12 - Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. statutory federal tax rate	21.00%	21.00%	21.00%
Foreign income at lower rates	(15.20%)	(20.70%)	(22.00%)
One-time deemed repatriation transition tax	0.00%	0.00%	0.60%
GILTI	11.10%	11.00%	14.40%
Changes in valuation allowance	1.60%	2.10%	0.00%
Stock-based compensation	(11.20%)	(1.50%)	(1.10%)
Tax credits, net of reserves	(3.80%)	(6.20%)	(1.90%)
State income taxes	(1.60%)	(0.70%)	0.00%
Other adjustments	1.00%	(1.20%)	0.20%
Effective tax rate	2.90%	3.80%	11.20%