Leases - Narrative (Details)	3 Months Ended	12 Months Ended
	Sep. 26, 2020 USD ($)	Sep. 26, 2020 USD ($)	Sep. 28, 2019 USD ($)	Sep. 29, 2018 USD ($)	Sep. 29, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Period with option to terminate lease		1 year
Extension period		20 years
Weighted average discount rate		0.0262
Finance lease liabilities (current)			$ 1,800,000
Finance lease liabilities (non-current)			19,200,000
Rent expense			23,100,000	$ 23,100,000
Lease revenue as a percentage of total	0.04
Right-of-use asset obtained in exchange for finance lease liability		$ 10,200,000
Lease receivable	$ 19,300,000	19,300,000
Rent expense on sublease rentals		2,000,000.0	2,700,000	2,600,000
Operating lease, right-of-use assets	80,700,000	80,700,000	0		$ 91,700,000
Finance Lease, Right-of-Use Asset					10,200,000
Present value of lease liabilities	89,100	89,100			96,600,000
Present value of lease liabilities	19,300	19,300			$ 21,000,000.0
Property, plant and equipment, net	(491,500,000)	(491,500,000)	(470,900,000)	$ (478,200,000)
Other long-term liabilities	$ (303,200,000)	$ (303,200,000)	$ (162,400,000)
Operating Lease, Liability, Statement of Financial Position [Extensible List]					us-gaap:LiabilitiesAbstract
Finance Lease, Liability, Statement of Financial Position [Extensible List]					us-gaap:LiabilitiesAbstract
Accounting Standards Update 2016-02 [Member]
Lessee, Lease, Description [Line Items]
Property, plant and equipment, net					$ 32,600,000
Other long-term liabilities					$ 35,200,000
Minimum
Lessee, Lease, Description [Line Items]
Lessee, operating and finance lease, remaining lease term		1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, operating and finance lease, remaining lease term		15 years