Restructuring and Other Charges (Additional Information) (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 28, 2019 USD ($)	Dec. 29, 2018 USD ($) employee	Sep. 30, 2019 USD ($) employee	Sep. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 14,034	$ 18,493
Restructuring charges	13,758	16,586
Total lease cost	11,533
Restructuring Reserve	27,606	10,691	$ 31,086	$ 2,415
Facility Impairment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	200
Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	127	243
Total lease cost	2,400
Restructuring Reserve	13,579	2,335	30,788	2,415
Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	13,631	16,343
Restructuring Reserve	14,027	8,356	298	$ 0
Accrued Expenses and Other Current Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	4,700	1,300
Other Noncurrent Liabilities [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	8,800	1,000
Restructuring Plan 2019 [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 16,600
Restructuring Plan 2019 [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	16,300
Number of employees | employee		240
2016 and 2019 Restructuring Plans [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Net Lease Commitments	28,000		$ 30,800
Gross Lease Commitments	35,100
Committed Sublease Income	3,700
Uncommitted Sublease Income	3,400
Prior Headquarters Relocation Charge [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 1,900
Restructuring Plan 2020 [Member]
Restructuring Cost and Reserve [Line Items]
Total estimated restructuring charges FY20	30,000
Restructuring Plan 2020 [Member] | Employee severance and related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	13,600
Number of employees | employee			175
Total estimated restructuring charges FY20	21,000
Prior Headquarters [Member] | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
Depreciation		$ 1,900
Accounting Standards Update 2016-02 | Facility closures and related costs
Restructuring Cost and Reserve [Line Items]
ASC 842 adoption	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
Facility Impairment [Member] | Facility Impairment [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 200