Note 12 - Income Taxes - Components of Income Before Income Tax (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
United States									$ (19,115)	$ (14,431)	$ (247)
Foreign									102,059	71,695	42,738
Income before income taxes	$ 26,700	$ 25,087	$ 16,207	$ 14,951	$ 18,439	$ 15,781	$ 12,124	$ 10,919	$ 82,944	$ 57,264	$ 42,491