Goodwill and Intangible Assets Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 29, 2019	Dec. 28, 2018	Mar. 30, 2018	Dec. 29, 2017	Mar. 29, 2019	Mar. 30, 2018	Sep. 28, 2018
Finite-Lived Intangible Assets [Line Items]
Cost	$ 416,635				$ 416,635		$ 400,166
Accumulated Amortization	(229,606)				(229,606)		(216,147)
Total	187,029				187,029		184,019
Purchases of intangible assets	$ 5,000	$ 12,100	$ 2,800	$ 12,000	$ 17,100	$ 14,800
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life	4 years	11 years 7 months 6 days	5 years 3 months 18 days	14 years 1 month 6 days	9 years 3 months 18 days	12 years 6 months
Amortization of Intangible Assets	$ 7,400		$ 6,600		$ 14,100	$ 13,100
Acquired Patents And Technology [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	331,493				331,493		319,082
Accumulated Amortization	(164,221)				(164,221)		(152,775)
Total	167,272				167,272		166,307
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	62,424				62,424		58,342
Accumulated Amortization	(43,013)				(43,013)		(41,012)
Total	19,411				19,411		17,330
Other Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Cost	22,718				22,718		22,742
Accumulated Amortization	(22,372)				(22,372)		(22,360)
Total	$ 346				$ 346		$ 382