Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	$ 1,456	$ 983
Balance at end of period	1,702	1,027
Uncovered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	0	1
Covered Litigation
Loss Contingency Accrual [Roll Forward]
Provision for legal matters	347	146
Payments for legal matters	(101)	(103)
U.S. Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	1,441	881
Provision for legal matters	341	145
Payments for legal matters	(101)	0
Balance at end of period	1,681	1,026
VE Territory Covered Litigation
Loss Contingency Accrual [Roll Forward]
Balance at beginning of period	11	102
Provision for legal matters	6	1
Payments for legal matters	0	(102)
Balance at end of period	$ 17	$ 1