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Income Taxes - Additional Information (Detail) - USD ($) | 12 Months Ended |
--- | --- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021
Income Taxes [Line Items] |  |  |  |
Other tax credit carryforwards | $ 144,000,000 |  |  |
Undistributed earnings | 1,700,000,000 |  |  |
Unrecognized tax benefits | 22,000,000 | $ 20,000,000 | $ 159,000,000 | $ 21,000,000
Unrecognized tax benefits, offset against deferred tax assets | 13,000,000 | 14,000,000 |  |
Non cash income tax expense (benefit) | 24,000,000 | 152,000,000 |  |
Accruals for penalties and interest | 10,000,000 | 5,000,000 |  |
Total penalties and interest | 5,000,000 | 2,000,000 | 2,000,000 |
Favorable impact on tax provision | 22,000,000 |  |  |
Purification Solutions [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Income tax benefit from tax loss related to divestiture |  | 137,000,000 | $ 137,000,000 |
Other Liabilities [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Unrecognized tax benefits, recorded | 9,000,000 | 6,000,000 |  |
Maximum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Other tax credit carryforwards | $ 1,000,000 |  |  |
Maximum [Member] | United States Internal Revenue Service (IRS) [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2023 |  |  |
Minimum [Member] | United States Internal Revenue Service (IRS) [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2021 |  |  |
Foreign Jurisdictions [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
NOLs | $ 35,000,000 |  |  |
Foreign Jurisdictions [Member] | Maximum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2023 |  |  |
Foreign Jurisdictions [Member] | Minimum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2006 |  |  |
State Tax Authorities [Member] | Maximum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2023 |  |  |
State Tax Authorities [Member] | Minimum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Tax years remain subject to examination | 2018 |  |  |
U.S. Defined Benefit Plans [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Increased/(decreased) valuation in allowance | $ 494,000,000 |  |  |
U.S. Defined Benefit Plans [Member] | Maximum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Increased/(decreased) valuation in allowance |  | 498,000,000 |  |
U.S. Defined Benefit Plans [Member] | Minimum [Member] |  |  |  |
Income Taxes [Line Items] |  |  |  |
Increased/(decreased) valuation in allowance |  | $ (4,000,000) |  |

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