Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Dec. 31, 2024 |
Dec. 31, 2023 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | $ 1,727 | $ 1,751 |
| Balance at end of period | 1,649 | 1,471 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 17 | 10 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 34 | 22 |
| Payments for legal matters | (129) | (312) |
| U.S. Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 1,537 | 1,621 |
| Provision for legal matters | 27 | 0 |
| Payments for legal matters | 0 | (160) |
| Balance at end of period | 1,564 | 1,461 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 72 | 110 |
| Provision for legal matters | 7 | 22 |
| Payments for legal matters | (21) | (126) |
| Balance at end of period | $ 58 | $ 6 |