CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Net sales	$ 285,247	$ 250,694	$ 785,774	$ 710,077
Cost of goods sold	188,900	170,071	525,377	490,417
Gross profit	96,347	80,623	260,397	219,660
Operating expenses
Selling, general and administrative	43,525	38,321	122,912	119,165
Research and development	20,379	17,088	58,215	52,247
Amortization of acquisition related intangible assets	4,694	5,117	14,098	15,379
Impairment of fixed assets	1,993		1,993
Restructuring expense	2,039		6,108
Other operating expenses		144	169	184
Total operating expenses	72,630	60,670	203,495	186,975
Income from operations	23,717	19,953	56,902	32,685
Other income (expense)
Interest income	389	321	992	1,075
Interest expense	(3,561)	(3,684)	(10,493)	(9,880)
Foreign currency loss, net	(1,312)	(1,439)	(6,734)	(2,045)
Other income	597	480	1,128	551
Total other income (expense)	(3,887)	(4,322)	(15,107)	(10,299)
Income before income taxes and noncontrolling interest	19,830	15,631	41,795	22,386
Income tax provision	5,052	4,097	11,651	5,941
Net income	14,778	11,534	30,144	16,445
Less net income attributable to noncontrolling interest	(328)	(886)	(1,298)	(1,778)
Net income attributable to common stockholders	$ 14,450	$ 10,648	$ 28,846	$ 14,667
Earnings per share attributable to common stockholders:
Basic	$ 0.29	$ 0.22	$ 0.59	$ 0.30
Diluted	$ 0.29	$ 0.21	$ 0.58	$ 0.30
Number of shares used in earnings per share computation:
Basic	49,057	48,814	48,633	48,496
Diluted	50,416	49,922	50,061	49,565