Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Oct. 01, 2017	Sep. 30, 2018	Oct. 01, 2017
Income Statement [Abstract]
Revenue	$ 232,221	$ 266,042	$ 613,052	$ 583,161
Cost of revenue	58,860	68,061	153,227	142,757
Gross margin	173,361	197,981	459,825	440,404
Research, development, and engineering expenses	29,700	26,078	87,664	72,225
Selling, general, and administrative expenses	65,817	61,054	196,266	160,093
Operating income	77,844	110,849	175,895	208,086
Foreign currency gain (loss)	(379)	(127)	(708)	(574)
Investment income	3,937	2,475	10,736	6,625
Other income (expense)	(129)	(445)	(98)	(344)
Income before income tax expense	81,273	112,752	185,825	213,793
Income tax expense (benefit)	837	10,259	11,976	9,334
Net Income	$ 80,436	$ 102,493	$ 173,849	$ 204,459
Net income per weighted-average common and common-equivalent share:
Basic (usd per share)	$ 0.47	$ 0.59	$ 1.01	$ 1.18
Diluted (usd per share)	$ 0.45	$ 0.57	$ 0.98	$ 1.14
Weighted-average common and common-equivalent shares outstanding:
Basic (shares)	172,189	173,234	172,613	173,052
Diluted (shares)	177,245	179,354	178,021	179,124
Cash dividends per common share (usd per share)	$ 0.0450	$ 0.0425	$ 0.1350	$ 0.1225