Restructuring and Other Charges (Additional Information) (Details) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	Oct. 01, 2019 USD ($)	Mar. 28, 2020 USD ($)	Mar. 30, 2019 USD ($)	Mar. 28, 2020 USD ($)	Mar. 30, 2019 USD ($) employee	Sep. 30, 2019 USD ($) employee	Sep. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ (13,200)	$ (26,400)	$ (26,996)	$ (42,971)
Total lease cost		10,965		22,498
Restructuring Reserve		24,668	32,238	24,668	32,238	$ 31,086	$ 2,415
Impairment and Accretion Exited Lease Facilities [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		(4,700)		(5,000)
Accelerated Depreciation Planned Facility Exit [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges				(300)
Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges				4,362	(26,937)
Restructuring Reserve		7,183	31,283	7,183	31,283	30,788	2,415
Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges				(31,358)	(16,034)
Restructuring Reserve		17,485	955	17,485	955	$ 298	$ 0
Accrued Expenses and Other Current Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve		2,600	12,400	2,600	12,400
Other Noncurrent Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve		4,600	18,900	4,600	18,900
Total Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		(18,200)	(27,000)	(32,300)	(45,500)
Prior Headquarters Relocation Charge [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges			(600)	4,400	(2,500)
Restructuring Plan 2020 [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges				(31,500)
Number of employees | employee						255
Restructuring Plan 2019 [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 100			$ (16,300)
Number of employees | employee					240
Prior Headquarters [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Depreciation					$ 1,900
Operating Leases, Rent Expense			$ 600
Accounting Standards Update 2016-02 | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption	$ 16,500			16,462
Accounting Standards Update 2016-02 | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption				$ 0
Accounting Standards Update 2016-02 | Operating Lease ROU Asset [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption	7,600
Accounting Standards Update 2016-02 | Operating Lease Short Term Lease Obligation [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption	9,200
Accounting Standards Update 2016-02 | Operating Lease Long Term Lease Obligation [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption	$ 14,900