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Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2025 | Jun. 30, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Jun. 30, 2025 | Jun. 30, 2024
Other Income (Expense) [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Foreign exchange losses |  |  |  |  |  | $ (42)
Investment income (loss) | $ 1 |  |  |  | $ 2 | 16
Other Income (Expense) [Member] | Revaluation of Non-functional Currency [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Foreign exchange losses | $ (3) | $ (2) |  |  | $ (5) | $ (42)
Other Income (Expense) [Member] | Single Devaluation Action [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Foreign exchange losses |  |  |  | $ (33) |  |
BOPREAL Bonds [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Foreign exchange losses |  | (2) |  |  |  |
Purchase of bonds to settle foreign payables |  | $ 8 | $ 30 |  |  |
Investment income (loss) |  |  | (8) |  |  |
Proceeds from sale of bonds |  |  | $ 22 |  |  |

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