Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Dec. 29, 2018	Dec. 28, 2019	Sep. 29, 2019	Sep. 30, 2018
Significant Accounting Policies [Line Items]
Right-of-use assets recorded upon adoption of new leases standard		$ 7,891
Lease liabilities recorded upon adoption of new leases standard		$ 8,459
Potentially dilutive securities excluded from the computation of diluted earnings per share because their effect would have been antidilutive (in shares)	28.8
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	$ 89
Retained earnings
Significant Accounting Policies [Line Items]
Increase in AOCI and decrease in retained earnings upon adoption of ASU 2017-12			(136)	$ 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)