Note 12 - Income Taxes - Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
U.S. statutory federal tax rate	21.00%	35.00%	34.00%
Foreign income at lower rates	(22.00%)	(41.20%)	(41.10%)
Remeasurement of deferred taxes		11.80%
One-time deemed repatriation transition tax	0.60%	50.50%
Global intangible low-taxed income ("GILTI")	14.40%
Changes in valuation allowance		(36.20%)	11.00%
Stock-based compensation	(1.10%)	2.20%	2.20%
Other adjustments	(1.70%)	(0.70%)	1.80%
Effective tax rate	11.20%	21.40%	7.90%