Note 10 - Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax provision at U.S federal statutory rate		$ 49,639	$ 44,638	$ 31,347
State and local taxes, net of federal income tax benefit		(207)	(2,310)	(2,450)
Effect of foreign income taxed at rates other than the U.S. federal statutory rate		(1,989)	(1,154)	989
Foreign income inclusions				5,017
Tax credits		(100)	(200)	(4,685)
Net change in valuation allowance		(315)	1,673	3,134
Domestic production deduction		(3,347)	(2,327)	(1,958)
Share-based payment compensation		(5,236)
Changes in tax laws	$ 117	117
Permanent items and other		(501)	(106)	995
Total income tax expense		$ 38,061	$ 40,214	$ 32,389