Leases - Supplemental Balance Sheet Information (Details) - USD ($)	Sep. 26, 2020	Sep. 29, 2019	Sep. 28, 2019
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use assets	$ 80,700,000	$ 91,700,000	$ 0
Operating lease liabilities (current)	$ 23,500,000		0
Finance lease liabilities (current)			$ 1,800,000
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent
Operating lease liabilities (non-current)	$ 65,600,000		$ 0
Finance lease liabilities (non-current)			$ 19,200,000
Operating leases, weighted average remaining lease term	5 years 6 months 29 days
Finance leases, weighted average remaining lease term	7 years 7 months 20 days
Operating leases, weighted average discount rate	2.00%
Finance leases, weighted average discount rate	5.10%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent		us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Other assets
Lessee, Lease, Description [Line Items]
Operating lease, right-of-use assets	$ 80,700
Accrued expenses
Lessee, Lease, Description [Line Items]
Operating lease liabilities (current)	23,500
Other long-term liabilities
Lessee, Lease, Description [Line Items]
Operating lease liabilities (non-current)	65,600
Finance lease obligations - short term
Lessee, Lease, Description [Line Items]
Finance lease liabilities (current)	1,900
Finance lease obligations - long term
Lessee, Lease, Description [Line Items]
Finance lease liabilities (non-current)	$ 17,400