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Income Taxes - Additional Information (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Mar. 31, 2025 | Mar. 31, 2024 | Mar. 31, 2025 | Mar. 31, 2024
Minimum [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Decrease in unrecognized tax benefits is reasonably possible | $ 2 |  | $ 2 |
Maximum [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Decrease in unrecognized tax benefits is reasonably possible | $ 4 |  | $ 4 |
Current Fiscal Year [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Effective tax rate (in hundredths) | 23.00% |  | 20.00% |
Tax (benefit) and expense |  |  | $ 7 |
Prior Fiscal Year [Member] |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |
Effective tax rate (in hundredths) |  | 612.00% |  | 610.00%
Tax (benefit) and expense |  | $ (102) |  | $ (126)

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