Restructuring and Other Charges (Additional Information) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 29, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 29, 2019 USD ($) employee	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 9	$ (1,627)	$ (45,464)	$ (1,846)
Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Sublease Income Assumed	13,700		13,700
Committed Sublease Income	1,400		1,400
Uncommitted Sublease Income	12,300		12,300
Accrued Expenses and Other Current Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	12,100	1,600	12,100	1,600
Other Noncurrent Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	16,300	1,100	16,300	1,100
Restructuring Plan 2019 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ (16,000)
Restructuring and Related Cost, Number of Positions Eliminated | employee			240
Prior Year Plans [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			$ (100)
2016 and 2019 Restructuring Plans [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			(42,962)
Restructuring Reserve	28,771		28,771		$ 2,415
2016 and 2019 Restructuring Plans [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			(15,719)
Restructuring Reserve	328		328		0
2016 and 2019 Restructuring Plans [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			(27,243)
Restructuring Reserve	28,443		28,443		2,415
Gross Lease Commitments	42,100		42,100
Prior Headquarters Relocation Charge [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net			(2,500)	(2,900)
Restructuring Plan 2016 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				1,014
Restructuring Reserve		2,716		2,716		$ 6,244
Restructuring Plan 2016 [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				509
Restructuring Reserve		0		0		1,736
Restructuring Plan 2016 [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net				505
Restructuring Reserve		$ 2,716		2,716	$ 2,400	$ 4,508
Prior Headquarters [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ (400)		(27,100)
Depreciation			1,900	$ 2,900
Payments for Rent			$ 600