Restructuring and Other Charges - Additional Information (Details) $ in Thousands		3 Months Ended	12 Months Ended
	Oct. 02, 2019 USD ($)	Dec. 28, 2018 USD ($) Employee	Sep. 30, 2020 USD ($) Employee	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net			$ (32,716)	$ (51,114)	$ (3,764)
Restructuring Charges			(26,427)	(48,612)	1,003
Payments for restructuring			31,502	24,721	2,756
Restructuring Reserve			9,987	31,086	2,415	$ 6,244
Depreciation			24,700	26,700	29,400
Impairment and Accretion Exited Lease Facilities
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net			(5,600)
Accelerated Depreciation Planned Facility Exit
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net			(700)
Facility Closures
Restructuring Cost And Reserve [Line Items]
Restructuring Charges			4,263	(32,908)	494
Payments for restructuring			4,246	9,319	1,509
Restructuring Reserve			5,995	30,788	2,415	4,508
Facility Closures | Accrued Expenses and Other Current Liabilities
Restructuring Cost And Reserve [Line Items]
Restructuring Reserve			2,800
Facility Closures | Other Noncurrent Liabilities
Restructuring Cost And Reserve [Line Items]
Restructuring Reserve			3,200	18,900
Facility Closures | Other Current Liabilities
Restructuring Cost And Reserve [Line Items]
Restructuring Reserve				11,900
Facility Closures | Accounting Standards Update 2016-02
Restructuring Cost And Reserve [Line Items]
ASC 842 adoption	$ 16,500
Facility Closures | Accounting Standards Update 2016-02 | Operating Lease ROU Asset
Restructuring Cost And Reserve [Line Items]
ASC 842 adoption	7,600
Facility Closures | Accounting Standards Update 2016-02 | Operating Lease Short Term Lease Obligation
Restructuring Cost And Reserve [Line Items]
ASC 842 adoption	9,200
Facility Closures | Accounting Standards Update 2016-02 | Operating Lease Long Term Lease Obligation
Restructuring Cost And Reserve [Line Items]
ASC 842 adoption	$ 14,900
Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Charges			(30,690)	(15,704)	509
Payments for restructuring			27,256	15,402	1,247
Restructuring Reserve			3,992	298	0	$ 1,736
Prior Headquarters Relocation Charge
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net			$ 4,300
Restructuring Charges				(32,700)
Lease expiration, month and year			2022-11
Restructuring Plan 2020
Restructuring Cost And Reserve [Line Items]
Payments for restructuring			$ 27,300
Restructuring Plan 2020 | Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Charges			$ (30,800)
Number of employees | Employee			250
Restructuring Plan 2019
Restructuring Cost And Reserve [Line Items]
Payments for restructuring			$ 3,900	23,600
Restructuring Plan 2019 | Employee Severance and Related Benefits
Restructuring Cost And Reserve [Line Items]
Restructuring Charges		$ (16,300)	100
Number of employees | Employee		240
Restructuring Plan 2016
Restructuring Cost And Reserve [Line Items]
Restructuring Charges					(200)
Payments for restructuring			$ 300	1,100	2,600
2016 and 2019 Restructuring Plans
Restructuring Cost And Reserve [Line Items]
Restructuring Charges				(48,600)
Prior Year Plans | Facility Closures
Restructuring Cost And Reserve [Line Items]
Restructuring Charges				(200)
Prior Headquarters Relocation Charge | Facility Closures
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net				(2,500)
Restructuring Plan 2015
Restructuring Cost And Reserve [Line Items]
Restructuring Charges					(800)
Payments for restructuring					200
Prior Headquarters | Facility Closures
Restructuring Cost And Reserve [Line Items]
Depreciation				1,900	$ 4,800
Payments for Rent				$ 600