Legal Matters - Schedule of Accrued Litigation for Both Covered and Non-Covered Litigation (Detail) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | $ 983 | $ 914 |
| Balance at end of period | 1,027 | 909 |
| Uncovered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 1 | 1 |
| Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Provision for legal matters | 146 | 10 |
| Payments for legal matters | (103) | (16) |
| U.S. Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 881 | 888 |
| Provision for legal matters | 145 | 0 |
| Payments for legal matters | 0 | (7) |
| Balance at end of period | 1,026 | 881 |
| VE Territory Covered Litigation | ||
| Loss Contingency Accrual [Roll Forward] | ||
| Balance at beginning of period | 102 | 21 |
| Provision for legal matters | 1 | 10 |
| Payments for legal matters | (102) | (9) |
| Balance at end of period | $ 1 | $ 22 |