CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Net sales	$ 1,229,215	$ 1,249,130	$ 1,213,989
Cost of goods sold	798,094	783,323	778,713
Gross profit	431,121	465,807	435,276
Operating expenses
Selling, general and administrative	185,067	181,343	176,197
Research and development	94,288	88,517	86,286
Amortization of acquisition-related intangible assets	16,261	18,041	18,351
Loss (gain) on disposal of fixed assets	106	(24,429)	(636)
Other operating expense	1,067	1,727	596
Total operating expenses	296,789	265,199	280,794
Income from operations	134,332	200,608	154,482
Other income (expense)
Interest income	1,066	2,189	1,978
Interest expense	(11,662)	(7,893)	(9,901)
Foreign currency loss, net	(9,814)	(3,737)	(3,701)
Other income	6,419	7,079	7,104
Total other expense	(13,991)	(2,362)	(4,520)
Income before income taxes and noncontrolling interest	120,341	198,246	149,962
Income tax provision	21,112	44,131	44,556
Net income	99,229	154,115	105,406
Less: net income attributable to noncontrolling interest	(1,141)	(865)	(1,385)
Net income attributable to common stockholders	$ 98,088	$ 153,250	$ 104,021
Earnings per share attributable to common stockholders
Basic	$ 1.92	$ 3.02	$ 2.09
Diluted	$ 1.88	$ 2.96	$ 2.04
Number of shares used in computation
Basic	51,004	50,787	49,841
Diluted	52,133	51,860	50,935