Note 12 - Income Taxes (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Transition Tax Liability	$ 24,600
Payment for the Transition Tax	1,300	$ 2,600
GILTI Income	58,600	81,100
Undistributed Earnings of Foreign Subsidiaries	$ 32,900
Percent of Dividend Received Deduction	100.00%
Unrecognized Tax Benefits, Ending Balance	$ 25,407	20,491	$ 16,272	$ 14,431
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	17,300	12,800
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	1,600	900
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	12,600
State and Local Jurisdiction [Member] | Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards, Total	24,100
Bermuda Subsidiary [Member]
Foreign Earnings Repatriated	75,000
Accrued Liabilities, Current [Member]
Transition Tax Liability	2,000	1,300
Income Tax Liabilities, Noncurrent [Member]
Transition Tax Liability	$ 18,700	$ 20,700