Summary of Significant Accounting Policies (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 27, 2021 USD ($) store	Jun. 28, 2020 USD ($)	Jun. 27, 2021 USD ($) store	Jun. 28, 2020 USD ($)	Sep. 28, 2020 USD ($)	Sep. 27, 2020 USD ($)
Payroll Tax Incentives	$ 56.4	$ 266.0	$ 173.7	$ 301.0
Government subsidies receivables	161.7		161.7			$ 155.1
Deferred Payroll Tax Payments	0.0		81.7
Deferred Payroll Tax Payments, Current	116.4		116.4
Deferred Payroll Tax Payments, Noncurrent	116.4		116.4			151.0
Restructuring and Related Cost, Incurred Cost	19.8		115.0
Retained Earnings (Accumulated Deficit)	(7,501.6)		(7,501.6)			(7,815.6)
Accrued payroll and benefits	741.0		741.0			696.0
Other accrued restructuring Liabilities	8.7		$ 8.7			0.0
Accounting Standards Update 2016-13 [Member]
Retained Earnings (Accumulated Deficit)					$ 2.2
Minimum [Member]
Timing of Store Closures			6
Restructuring and Related Cost, Expected Cost	20.0		$ 20.0
Maximum [Member]
Timing of Store Closures			12
Restructuring and Related Cost, Expected Cost	30.0		$ 30.0
Facility Closing [Member]
Restructuring and Related Cost, Incurred Cost	7.8		59.0
Accelerated Lease ROU Asset Amortization and Other Lease Costs [Member]
Restructuring and Related Cost, Incurred Cost	12.2	$ 13.4	56.2	$ 17.0
Employee Severance [Member]
Accrued payroll and benefits	$ 1.8		$ 1.8			$ 15.2
US and Canada [Member]
Number of Store Closures | store	820		820
Identified Store Closures | store	790		790