Goodwill and Intangible Assets (Schedule Of Intangible Assets Subject To Amortization) (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 26, 2020	Sep. 27, 2019
Finite-Lived Intangible Assets [Line Items]
Document Period End Date	Jun. 26, 2020
Accumulated Amortization	$ (102.5)	$ (74.5)
Total intangible assets, Gross Carrying Amount	165.4	182.4
Total intangible assets, Net Carrying Amount	$ 62.9	107.9
Customer relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	5 years
Finite-Lived Intangible Assets, Gross	$ 18.2	25.6
Accumulated Amortization	(14.8)	(19.5)
Net Carrying Amount	$ 3.4	6.1
Technology-Based Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	3 years 9 months 18 days
Finite-Lived Intangible Assets, Gross	$ 101.0	94.4
Accumulated Amortization	(74.5)	(48.9)
Net Carrying Amount	$ 26.5	45.5
Trade Names [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	3 years
Finite-Lived Intangible Assets, Gross	$ 1.6	1.6
Accumulated Amortization	(1.6)	(1.3)
Net Carrying Amount	0.0	0.3
Computer Software, Intangible Asset [Member]
Finite-Lived Intangible Assets [Line Items]
Accrued Liabilities	$ 11.9	20.1
Weighted Average Amortization Period (Years)	3 years 1 month 6 days
Finite-Lived Intangible Assets, Gross	$ 25.1	24.9
Accumulated Amortization	(11.6)	(4.8)
Net Carrying Amount	$ 13.5	20.1
In Process Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted Average Amortization Period (Years)	0 years
Finite-Lived Intangible Assets, Gross	$ 19.5	35.9
Accumulated Amortization	0.0	0.0
Net Carrying Amount	$ 19.5	$ 35.9