Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	35.00%	34.00%
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability			$ 9,800
Transition tax			41,900
Utilization of R&D tax credit			18,000
Transition Tax Liability	$ 23,900	$ 24,600	23,900
Transition Tax, Increase		1,300
Transition Tax Liability, Increase		700
Payment for the Transition Tax		2,600
Deferred Income Tax Liabilities, Net, Total		0
Undistributed Earnings of Foreign Subsidiaries		390,200
Undistributed Foreign Earnings Subject to Tax		123,200
Undistributed Foreign Earnings, Deferred Tax		1,100
GILTI Income		81,100
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(21,600)
Unrecognized Tax Benefits, Ending Balance	16,272	20,491	16,272	$ 14,431	$ 12,093
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	9,100	12,800	9,100
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	$ 500	900	$ 500
Domestic Tax Authority [Member]
Operating Loss Carryforwards, Total		0
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax Credit Carryforward, Amount		0
State and Local Jurisdiction [Member] | Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards, Total		16,200
State and Local Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards, Total		24,100
Accrued Liabilities, Current [Member]
Transition Tax Liability		1,300
Income Tax Liabilities, Noncurrent [Member]
Transition Tax Liability		$ 20,700