Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions	9 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 1,751	$ 1,456
Balance at end of period	1,688	1,545
Uncovered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	311	1
Covered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	201	808
Payments for legal matters	(575)	(720)
U.S. Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	1,621	1,441
Provision for legal matters	140	797
Payments for legal matters	(204)	(699)
Balance at end of period	1,557	1,539
VE Territory Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	110	11
Provision for legal matters	61	11
Payments for legal matters	(146)	(19)
Balance at end of period	$ 25	$ 3