CONDENSED CONSOLIDATED STATEMENTS OF NET INCOME - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 26, 2020	Sep. 28, 2019	Sep. 26, 2020	Sep. 28, 2019
Income Statement [Abstract]
Net sales	$ 391,566	$ 361,971	$ 1,044,999	$ 1,165,350
Cost of sales	253,390	231,025	684,012	737,368
Gross profit	138,176	130,946	360,987	427,982
Selling, general, and administrative expenses	50,465	54,224	158,832	174,845
Goodwill impairment charge	0	0	33,841	0
Research and development expenses	13,049	19,728	41,044	62,595
Amortization of intangibles	10,104	9,827	29,912	30,068
Total operating expenses	73,618	83,779	263,629	267,508
Operating income	64,558	47,167	97,358	160,474
Interest expense	4,988	5,559	16,261	16,834
Foreign exchange (gain) loss	(6,174)	4,968	(9,600)	5,636
Other income, net	(1,682)	(4,764)	(1,643)	(3,406)
Income before income taxes	67,426	41,404	92,340	141,410
Income taxes	12,070	5,757	21,331	24,982
Net income	$ 55,356	$ 35,647	$ 71,009	$ 116,428
Income per share:
Basic (in dollars per share)	$ 2.27	$ 1.46	$ 2.92	$ 4.72
Diluted (in dollars per share)	$ 2.25	$ 1.44	$ 2.89	$ 4.68
Weighted-average shares and equivalent shares outstanding:
Basic (in shares)	24,357	24,482	24,354	24,646
Diluted (in shares)	24,573	24,684	24,535	24,894