Legal Matters - Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Sep. 30, 2023 |
Sep. 30, 2022 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | $ 1,456 | $ 983 |
| Balance as of end of period | 1,751 | 1,456 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 21 | 6 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 1,024 | 885 |
| Payments on legal matters | (750) | (418) |
| U.S. Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | 1,441 | 881 |
| Provision for legal matters | 906 | |
| Payments on legal matters | (726) | (301) |
| Balance as of end of period | 1,621 | 1,441 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | 11 | 102 |
| Provision for legal matters | 118 | 24 |
| Payments on legal matters | (19) | (115) |
| Balance as of end of period | $ 110 | $ 11 |