Note 12 - Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
U.S. statutory federal tax rate	21.00%	21.00%	35.00%
Foreign income at lower rates	(20.70%)	(22.00%)	(41.20%)
Remeasurement of deferred taxes			11.80%
One-time deemed repatriation transition tax		0.60%	50.50%
Global intangible low-taxed income (“GILTI”)	11.00%	14.40%
Changes in valuation allowance	2.10%		(36.20%)
Stock-based compensation	(1.50%)	(1.10%)	2.20%
Tax credits	(6.20%)	(1.90%)	(2.10%)
Other adjustments	(1.90%)	0.20%	1.40%
Effective tax rate	3.80%	11.20%	21.40%