CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income (loss)	$ (100,639)	$ 93,221	$ 192,008
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	40,974	31,857	30,477
Stock-based compensation expense	14,270	12,217	13,125
Impairment and other non-cash charges	60,968	0	0
Loss (gain) on sale of equipment	(168)	(103)	69
Deferred income taxes	17,231	(3,400)	(3,465)
Changes in operating assets and liabilities:
Trade receivables, net	26,112	106,544	36,729
Inventories, net	37,642	7,873	28,539
Prepaids and other assets	10,107	9,816	(17,883)
Excess tax benefits of stock options and awards	0	(135)	(70)
Accounts payable and accrued expenses	1,765	(11,368)	(89,374)
Other, net	(269)	0	0
Net cash provided by operating activities	107,993	246,522	190,155
Investing activities
Purchase of property, plant and equipment	(27,622)	(25,763)	(27,079)
Proceeds from sale of equipment	3,170	357	424
Acquisition of business, net of cash acquired	(20,440)	(132,443)	0
Net cash used in investing activities	(44,892)	(157,849)	(26,655)
Financing activities
Proceeds from exercise of stock options	560	2,206	2,170
Excess tax benefits of stock options and awards	0	135	70
Repurchase of common shares	0	(24,234)	(75,805)
Net cash used in financing activities	560	(21,893)	(73,565)
Effect of exchange rate changes on cash activities	6,022	(24,619)	(7,304)
Increase (decrease) in cash and cash equivalents	69,683	42,161	82,631
Cash and cash equivalents at beginning of year	423,497	381,336	298,705
Cash and cash equivalents at end of year	$ 493,180	$ 423,497	$ 381,336