Leases - Narrative (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 01, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2020	Oct. 01, 2019
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets				$ 227,146
Operating lease liabilities				$ 236,787
Lease and rental expense		$ 40,400	$ 33,800
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201602Member
Cumulative effect of accounting change
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets					$ 231,300
Operating lease liabilities					231,300
Accrued and prepaid rent reclassified					6,500
Deferred rent credits and other liabilities reclassified					$ 2,500