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Derivative Financial Instruments - Narrative (Details) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2023
Derivatives, Fair Value [Line Items] |  |  |
Derivative, notional amount |  | $ 0 |
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax | $ 0 | (1,000,000) | $ (12,000,000)
Interest Rate Swap |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, notional amount | 0 | 0 |
Other comprehensive gain (loss), cash flow hedge, loss, after reclassification and tax | 0 | 0 |
Pre-tax gains (losses) of the company derivative interest rate swaps | 0 | (1,000,000) |
Foreign Exchange Contract | Other Nonoperating Income (Expense) |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Realized foreign exchange forward contract gain | 1,000,000 |  |
Unrealized foreign exchange forward contract gain (loss) | 3,000,000 |  |
Foreign Exchange Forward |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Losses on derivative, net |  | $ 1,000,000 |
Short |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, notional amount | 460,000,000 |  |
Long |  |  |
Derivatives, Fair Value [Line Items] |  |  |
Derivative, notional amount | $ 170,000,000 |  |

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