CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
Net sales	$ 1,054,204	$ 942,162	$ 848,904
Cost of goods sold	697,428	655,239	600,321
Gross profit	356,776	286,923	248,583
Operating expenses
Selling, general and administrative	167,639	158,256	139,245
Research and development	77,877	69,937	57,027
Amortization of acquisition related intangible assets	18,798	20,478	8,596
Impairment of fixed assets	2,211	114	1,672
Restructuring	10,137	12
Other operating expenses	(246)	70	(59)
Total operating expenses	276,416	248,867	206,481
Income from operations	80,360	38,056	42,102
Other (expense)/income
Interest income	1,475	1,357	1,006
Interest expense	(13,448)	(13,257)	(4,232)
Gain on securities carried at fair value			400
Foreign currency (loss) gain, net	(7,995)	2,171	1,257
Impairment of cost-basis investment		(3,218)
Other income (expense)	2,199	(74)	62
Total other (expense) income	(17,769)	(13,021)	(1,507)
Income before income taxes and noncontrolling interest	62,591	25,035	40,595
Income tax provision	62,325	6,558	14,082
Net income	266	18,477	26,513
Less: net (income) loss attributable to noncontrolling interest	(2,071)	(2,542)	(2,239)
Net (loss) income attributable to common stockholders	$ (1,805)	$ 15,935	$ 24,274
(Loss) earnings per share attributable to common stockholders
Basic	$ (0.04)	$ 0.33	$ 0.50
Diluted	$ (0.04)	$ 0.32	$ 0.49
Number of shares used in computation
Basic	48,824	48,597	48,210
Diluted	48,824	49,789	49,500