Income Taxes (Income Tax Expense Reconciliation) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Income Tax Disclosure [Abstract]
Tax expense at United States statutory rate	$ 201.8	$ 327.4	$ 439.9
Foreign tax rate difference	(115.3)	(111.9)	(174.6)
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	8.1	224.6	0.0
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Compensation Cost, Amount	(1.6)	(25.6)	0.0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	0.0	18.3	0.0
Research and development credits	(25.7)	(19.9)	(16.3)
Change in tax reserve	14.0	6.7	12.6
Domestic production activities deduction	0.0	(13.9)	(19.8)
EffectiveIncomeTaxRateReconciliationGlobalIntangibleLowTaxedIncomeAmount	54.3	0.0	0.0
EffectiveIncomeTaxRateReconciliationForeignDerivedIntangibleIncome	(41.5)	0.0	0.0
Audit settlement and adjustment	4.3	0.0	0.0
Other, net	9.0	8.0	5.0
Provision for income taxes	$ 107.4	$ 413.7	$ 246.8