Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Apr. 01, 2018
Income Statement [Abstract]
Revenues	$ 173,484	$ 169,567
Cost of revenue	46,284	40,198
Gross margin	127,200	129,369
Research, development, and engineering expenses	30,242	31,076
Selling, general, and administrative expenses	66,811	63,697
Operating income	30,147	34,596
Foreign currency gain (loss)	(248)	(134)
Investment income	4,905	3,240
Other income (expense)	927	277
Income before income tax expense	35,731	37,979
Income tax expense (benefit)	2,627	762
Net income	$ 33,104	$ 37,217
Net income per weighted-average common and common-equivalent share:
Basic (in dollars per share)	$ 0.19	$ 0.21
Diluted (in dollars per share)	$ 0.19	$ 0.21
Weighted-average common and common-equivalent shares outstanding:
Basic (in shares)	171,098	173,280
Diluted (in shares)	175,607	179,641
Cash dividends per common share	$ 0.0500	$ 0.045