CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities
Cash flows from operating activities	$ 45,626	$ 25,453
Cash flows from investing activities
Decrease in restricted cash	854	3
Purchases of property, plant and equipment	(19,106)	(13,561)
Proceeds from sales of property, plant, and equipment	211	19
Purchases of short-term investments	(6,787)	(7,330)
Proceeds from maturity of short-term investments	4,588	29,289
Other	(155)	291
Net cash and cash equivalents (used in) provided by investing activities	(20,395)	8,711
Cash flows from financing activities
Taxes paid related to net share settlement		(2,335)
Debt issuance costs	(67)	(22)
Proceeds from long-term debt	7,500	1,500
Repayments of long-term debt	(18,701)	(15,569)
Net proceeds from issuance of common stock	2,166	5
Repayment of capital lease obligation and other	(1,238)	(843)
Net cash and cash equivalents used in financing activities	(10,340)	(17,264)
Effect of exchange rate changes on cash and cash equivalents	2,426	1,671
Increase in cash and cash equivalents	17,317	18,571
Cash and cash equivalents, beginning of period	247,802	218,435
Cash and cash equivalents, end of period	265,119	237,006
Non-cash financing activities:
Change in Accounts Payable related to the purchase of Property, plant and equipment	$ (7)	$ 697