CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement [Abstract]
Net sales	$ 320,946	$ 285,247	$ 899,543	$ 785,774
Cost of goods sold	205,732	188,900	578,466	525,377
Gross profit	115,214	96,347	321,077	260,397
Operating expenses
Selling, general and administrative	42,475	43,525	131,778	122,912
Research and development	22,549	20,379	64,799	58,215
Amortization of acquisition related intangible assets	4,418	4,694	13,863	14,098
Impairment of fixed assets		1,993		1,993
Restructuring		2,039	206	6,108
Other operating (income) expense	(66)		(191)	169
Total operating expense	69,376	72,630	210,455	203,495
Income from operations	45,838	23,717	110,622	56,902
Other income (expense)
Interest income	474	389	1,431	992
Interest expense	(2,318)	(3,561)	(7,619)	(10,493)
Foreign currency loss, net	(655)	(1,312)	(3,384)	(6,734)
Other income	1,061	597	6,073	1,128
Total other expense	(1,438)	(3,887)	(3,499)	(15,107)
Income before income taxes and noncontrolling interest	44,400	19,830	107,123	41,795
Income tax provision	13,190	5,052	31,726	11,651
Net income	31,210	14,778	75,397	30,144
Less net income attributable to noncontrolling interest	(302)	(328)	(895)	(1,298)
Net income attributable to common stockholders	$ 30,908	$ 14,450	$ 74,502	$ 28,846
Earnings per share attributable to common stockholders:
Basic	$ 0.62	$ 0.29	$ 1.50	$ 0.59
Diluted	$ 0.61	$ 0.29	$ 1.46	$ 0.58
Number of shares used in earnings per share computation:
Basic	50,115	49,057	49,713	48,633
Diluted	51,077	50,416	50,883	50,061