Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Jun. 30, 2022	Jun. 30, 2022	Jun. 30, 2021
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period		$ 983	$ 914
Balance at end of period	$ 1,486	1,486	900
Uncovered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters		2	5
Covered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters		878	23
Payments for legal matters		(377)	(42)
U.S. Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period		881	888
Provision for legal matters	716	861	0
Payments for legal matters		(262)	(7)
Balance at end of period	1,480	1,480	881
VE Territory Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period		102	21
Provision for legal matters		17	23
Payments for legal matters		(114)	(29)
Balance at end of period	$ 5	$ 5	$ 15