Summary of Significant Accounting Policies (Details) $ in Millions	3 Months Ended
	Dec. 27, 2020 USD ($) store	Sep. 28, 2020 USD ($)	Sep. 27, 2020 USD ($)
Payroll Tax Incentives	$ 19.8
Government subsidies receivables	149.3		$ 155.1
Deferred Payroll Tax Payments, Noncurrent	227.5
Deferred Payroll Tax Payments	$ 76.5
Identified Store Closures | store	713
Operating Lease, Liability	$ 9,022.1
Employee-related Liabilities, Current	685.3		696.0
Retained Earnings (Accumulated Deficit)	(8,253.6)		$ (7,815.6)
Restructuring and Related Cost, Incurred Cost	$ 72.2
Accounting Standards Update 2016-13 [Member]
Retained Earnings (Accumulated Deficit)		$ 2.2
Minimum [Member]
Timing of Store Closures	9
Restructuring and Related Cost, Expected Cost	$ 100.0
Maximum [Member]
Timing of Store Closures	12
Restructuring and Related Cost, Expected Cost	$ 120.0
Facility Closing [Member]
Restructuring and Related Cost, Incurred Cost	42.6
Facility Closing [Member] | Minimum [Member]
Restructuring and Related Cost, Expected Cost	10.0
Facility Closing [Member] | Maximum [Member]
Restructuring and Related Cost, Expected Cost	15.0
lease termination [Member]
Operating Lease, Liability	24.4
Restructuring and Related Cost, Incurred Cost	29.6
lease termination [Member] | Minimum [Member]
Restructuring and Related Cost, Expected Cost	90.0
lease termination [Member] | Maximum [Member]
Restructuring and Related Cost, Expected Cost	100.0
Employee Severance [Member]
Employee-related Liabilities, Current	$ 14.9
US and Canada [Member]
Number of Store Closures | store	800