Legal Matters - Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Sep. 30, 2025 |
Sep. 30, 2024 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | $ 1,727 | $ 1,751 |
| Balance as of end of period | 3,033 | 1,727 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 352 | 322 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 2,232 | 248 |
| Payments on legal matters | (1,278) | (594) |
| U.S. Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | 1,537 | 1,621 |
| Provision for legal matters | 2,210 | 140 |
| Payments on legal matters | (1,049) | (224) |
| Balance as of end of period | 2,698 | 1,537 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance as of beginning of period | 72 | 110 |
| Provision for legal matters | 22 | 108 |
| Payments on legal matters | (85) | (146) |
| Balance as of end of period | $ 9 | $ 72 |