Note 6 - Property, Plant and Equipment (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Depreciation	$ 29,970	$ 23,654	$ 21,196
Payments To Acquire Property, Plant, and Equipment and Capital Expenditures Incurred But Not Yet Paid	$ 53,900	$ 51,604