Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 02, 2017	Jul. 03, 2016	Jul. 02, 2017	Jul. 03, 2016
Income Statement [Abstract]
Revenue	$ 172,904	$ 147,274	$ 307,846	$ 243,479
Cost of revenue	37,471	35,213	65,696	56,181
Gross margin	135,433	112,061	242,150	187,298
Research, development, and engineering expenses	23,377	19,671	46,147	40,226
Selling, general, and administrative expenses	52,518	42,715	99,039	81,053
Operating income	59,538	49,675	96,964	66,019
Foreign currency gain (loss)	(184)	330	(447)	230
Investment income	2,138	1,447	4,150	2,584
Other income (expense)	(169)	222	101	429
Income from continuing operations before income tax expense	61,323	51,674	100,768	69,262
Income tax expense (benefit) on continuing operations	5,251	8,660	(959)	11,363
Net income from continuing operations	56,072	43,014	101,727	57,899
Net income from discontinued operations	0	(255)	0	(255)
Net Income	$ 56,072	$ 42,759	$ 101,727	$ 57,644
Basic earnings per weighted-average common and common-equivalent share:
Net income from continuing operations	$ 0.65	$ 0.51	$ 1.18	$ 0.68
Net income (loss) from discontinued operations	0.00	(0.01)	0.00	0.00
Net income	0.65	0.50	1.18	0.68
Diluted earnings per weighted-average common and common-equivalent share:
Net income from continuing operations	0.63	0.50	1.14	0.67
Net income (loss) from discontinued operations	0.00	(0.01)	0.00	(0.01)
Net income	$ 0.63	$ 0.49	$ 1.14	$ 0.66
Weighted-average common and common-equivalent shares outstanding:
Basic	86,639	85,107	86,480	85,024
Diluted	89,614	86,806	89,452	86,713
Cash dividends per common share	$ 0.085	$ 0.075	$ 0.160	$ 0.145