Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	6 Months Ended
	Mar. 30, 2019	Mar. 30, 2019	Mar. 28, 2020	Dec. 29, 2019	Sep. 29, 2019	Dec. 30, 2018	Sep. 30, 2018
Significant Accounting Policies [Line Items]
Right-of-use assets recorded upon adoption of new leases standard			$ 8,728
Lease liabilities recorded upon adoption of new leases standard			$ 9,254
Potentially dilutive securities excluded from the computation of diluted earnings per share because their effect would have been antidilutive (in shares)	31.1	30.0
Accumulated other comprehensive income/(loss)
Significant Accounting Policies [Line Items]
Increase in AOCI and decrease in retained earnings upon adoption of ASU 2017-12				$ 0	$ 136	$ 0	$ 89
Retained earnings
Significant Accounting Policies [Line Items]
Increase in AOCI and decrease in retained earnings upon adoption of ASU 2017-12				$ 0	(136)	$ 0	$ 2,501
Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Right-of-use assets recorded upon adoption of new leases standard					7,500
Lease liabilities recorded upon adoption of new leases standard					8,100
Accounting Standards Update 2017-12 | Accumulated other comprehensive income/(loss)
Significant Accounting Policies [Line Items]
Increase in AOCI and decrease in retained earnings upon adoption of ASU 2017-12					136
Accounting Standards Update 2017-12 | Retained earnings
Significant Accounting Policies [Line Items]
Increase in AOCI and decrease in retained earnings upon adoption of ASU 2017-12					$ (136)