Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Oct. 01, 2016	Sep. 30, 2017	Oct. 01, 2016
Income Statement [Abstract]
Product sales	$ 375,550	$ 349,934	$ 1,072,684	$ 1,017,478
Service sales	190,034	176,896	549,119	521,158
Total net sales	565,584	526,830	1,621,803	1,538,636
Cost of product sales	155,621	145,623	436,800	419,695
Cost of service sales	80,271	72,721	239,814	220,179
Selling and administrative expenses	135,194	123,861	395,908	382,793
Research and development expenses	33,782	30,418	97,471	92,434
Litigation provisions			10,018
Acquired in-process research and development			5,000
Purchased intangibles amortization	1,682	2,476	5,104	7,531
Total costs and operating expenses	406,550	375,099	1,190,115	1,122,632
Operating income	159,034	151,731	431,688	416,004
Interest expense	(14,750)	(11,707)	(41,558)	(32,809)
Interest income	9,516	5,426	25,229	14,340
Income from operations before income taxes	153,800	145,450	415,359	397,535
Provision for income taxes	17,696	20,594	41,876	50,410
Net income	$ 136,104	$ 124,856	$ 373,483	$ 347,125
Net income per basic common share	$ 1.71	$ 1.55	$ 4.67	$ 4.29
Weighted-average number of basic common shares	79,712	80,677	79,908	80,923
Net income per diluted common share	$ 1.69	$ 1.53	$ 4.63	$ 4.26
Weighted-average number of diluted common shares and equivalents	80,521	81,388	80,660	81,573