Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions |
6 Months Ended | |
|---|---|---|
Mar. 31, 2023 |
Mar. 31, 2022 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | $ 1,456 | $ 983 |
| Balance at end of period | 1,602 | 769 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 0 | 1 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 352 | 150 |
| Payments for legal matters | (206) | (365) |
| 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 | (201) | (262) |
| Balance at end of period | 1,581 | 764 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 11 | 102 |
| Provision for legal matters | 11 | 5 |
| Payments for legal matters | (5) | (102) |
| Balance at end of period | $ 17 | $ 5 |