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Significant Accounting Policies - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2021
Significant Accounting Policies [Line Items] |  |  |
Equity affiliate investments | $ 20,000,000 | $ 20,000,000 |
Capitalized interest | 6,000,000 | 3,000,000 | $ 1,000,000
Asset retirement obligation reserve | 11,000,000 | 10,000,000 |
Changes in allowance | $ 0 | 0 | 0
Chance of utilizing the associated benefit for valuation allowances, maximum | 50.00% |  |
Equity Method Investments [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Dividends declared | $ 2,000,000 | 1,000,000 | 5,000,000
Minimum [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Payment terms | 0 days |  |
Minimum [Member] | Buildings [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 20 years |  |
Minimum [Member] | Machinery and Equipment [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 10 years |  |
Minimum [Member] | Other Fixed Assets [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 3 years |  |
Minimum [Member] | Cabot [Member] | Equity Affiliate Investments [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Equity method investment, ownership percentage | 20.00% |  |
Maximum [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Payment terms | 90 days |  |
Maximum [Member] | Buildings [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 25 years |  |
Maximum [Member] | Machinery and Equipment [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 25 years |  |
Maximum [Member] | Other Fixed Assets [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Useful life of property, plant and equipment | 25 years |  |
Maximum [Member] | Cabot [Member] | Equity Affiliate Investments [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Equity method investment, ownership percentage | 50.00% |  |
Other Nonoperating Income (Expense) [Member] |  |  |
Significant Accounting Policies [Line Items] |  |  |
Foreign currency transaction gain (loss) | $ (35,000,000) | $ (13,000,000) | $ (6,000,000)

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- Definition Valuation allowances are provided against deferred tax assets where management believes that the Company has a 50% or less chance of utilizing the associated benefit in the future. + References No definition available. + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 25 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481999/410-20-25-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 410 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481850/410-20-50-1 + Details
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