CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net income	$ 110	$ 72,906
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	22,713	15,500
Stock-based compensation expense	6,783	6,254
Loss (gain) on sale of equipment	(88)	(29)
Deferred income taxes	(1,486)	(3,828)
Changes in operating assets and liabilities:
Trade receivables, net	(4,823)	64,200
Inventories	29,246	763
Prepaids and other assets	4,471	20,658
Excess tax benefits of stock options and awards	0	(26)
Accounts payable and accrued expenses	(18,226)	(13,537)
Net cash provided by operating activities	38,700	162,861
Investing activities
Purchase of property, plant and equipment	(12,936)	(15,276)
Proceeds from sale of equipment	610	139
Acquisition of business, net of cash acquired	(21,289)	0
Net cash used in investing activities	(33,615)	(15,137)
Financing activities
Repurchase of common stock	0	24,238
Proceeds from exercise of stock options	403	508
Excess tax benefits of stock options and awards	0	26
Net cash used in financing activities	403	(23,704)
Effect of exchange rate changes on cash activities	8,002	(13,627)
Increase (decrease) in cash and cash equivalents	13,490	110,393
Cash and cash equivalents at beginning of period	423,497	381,336
Cash and cash equivalents at end of period	$ 436,987	$ 491,729