Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jul. 01, 2018	Jun. 30, 2019	Jul. 01, 2018
Income Statement [Abstract]
Revenue	$ 199,047	$ 211,264	$ 372,531	$ 380,831
Cost of revenue	50,967	54,169	97,251	94,367
Gross margin	148,080	157,095	275,280	286,464
Research, development, and engineering expenses	28,079	26,888	58,321	57,964
Selling, general, and administrative expenses	68,245	66,752	135,056	130,449
Operating income	51,756	63,455	81,903	98,051
Foreign currency gain (loss)	140	(195)	(108)	(329)
Investment income	5,223	3,559	10,128	6,799
Other income (expense)	(144)	(246)	783	31
Income before income tax expense	56,975	66,573	92,706	104,552
Income tax expense	8,226	10,377	10,853	11,139
Net Income	$ 48,749	$ 56,196	$ 81,853	$ 93,413
Net income per weighted-average common and common-equivalent share:
Basic (usd per share)	$ 0.28	$ 0.33	$ 0.48	$ 0.54
Diluted (usd per share)	$ 0.28	$ 0.32	$ 0.47	$ 0.52
Weighted-average common and common-equivalent shares outstanding:
Basic (shares)	171,318	172,370	171,209	172,825
Diluted (shares)	175,448	177,149	175,528	178,418
Cash dividends per common share (usd per share)	$ 0.050	$ 0.045	$ 0.100	$ 0.090