Acquisitions and Divestitures - Schedule of Aggregate Cash Consideration and Total Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Business Acquisition [Line Items]
Inventory	$ 2	$ 0
Other Current Assets	1	0
Property plant and equipment	93	1
Operating lease assets	36	0
Goodwill (b)	203	8
Other Current Liabilities	(8)	0
Operating Lease Liabilities	(33)	0
Other noncurrent liabilities	(84)	0
Net assets acquired	267	18
Consideration transferred	267	18
Financing lease assets	84
Financing lease liabilities, noncurrent	80
Financing lease liabilities, current	$ 4
Weighted average amortization period	10 years
Reacquired franchise rights (d)
Business Acquisition [Line Items]
Intangible assets	$ 54	9
Gain (Loss) on Contract Termination	$ 0
Weighted average amortization period	10 years
Other
Business Acquisition [Line Items]
Intangible assets	$ 3	$ 0