CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Net sales	$ 1,213,989	$ 1,054,204	$ 942,162
Cost of goods sold	778,713	697,428	655,239
Gross profit	435,276	356,776	286,923
Operating expenses
Selling, general and administrative	176,197	168,590	158,321
Research and development	86,286	77,877	69,937
Amortization of acquisition-related intangible assets	18,351	18,798	20,478
Impairment of fixed assets	390	2,211	114
Restructuring	206	10,137	12
Other operating (income) expense	(636)	(246)	70
Total operating expenses	280,794	277,367	248,932
Income from operations	154,482	79,409	37,991
Other income (expense)
Interest income	1,978	1,475	1,357
Interest expense	(9,901)	(13,448)	(13,257)
Foreign currency (loss) gain, net	(3,701)	(7,995)	2,171
Impairment of cost-basis investment			(3,218)
Other income (expense)	7,104	3,150	(9)
Total other expense	(4,520)	(16,818)	(12,956)
Income before income taxes and noncontrolling interest	149,962	62,591	25,035
Income tax provision	44,556	62,325	6,558
Net income	105,406	266	18,477
Less: net income attributable to noncontrolling interest	(1,385)	(2,071)	(2,542)
Net income (loss) attributable to common stockholders	$ 104,021	$ (1,805)	$ 15,935
Earnings (loss) per share attributable to common stockholders
Basic	$ 2.09	$ (0.04)	$ 0.33
Diluted	$ 2.04	$ (0.04)	$ 0.32
Number of shares used in computation
Basic	49,841	48,824	48,597
Diluted	50,935	48,824	49,789