Legal Matters - Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 983	$ 914
Balance at end of period	1,456	983
Uncovered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	6	4
Covered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	885	125
Payments on legal matters	(418)	(60)
U.S. Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	881	888
Provision for legal matters	861
Payments on legal matters	(301)	(7)
Balance at end of period	1,441	881
VE Territory Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	102	21
Provision for legal matters	24	125
Payments on legal matters	(115)	(44)
Balance at end of period	$ 11	$ 102