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Derivatives - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Sep. 30, 2024 | Sep. 30, 2023 | Sep. 30, 2022
Derivative [Line Items] |  |  |
Significant concentration of credit risk associated with our derivative instruments | $ 0 | $ 0 |
Maximum [Member] |  |  |
Derivative [Line Items] |  |  |
Fair value of derivative instruments not designated as hedges, liability | 1,000,000 | 1,000,000 |
Net Investment Hedge [Member] | Cross Currency Swaps [Member] |  |  |
Derivative [Line Items] |  |  |
Net cash interest received | 4,000,000 | 4,000,000 | $ 4,000,000
Fair value of swaps, net asset | 1,000,000 | 12,000,000 |
Cumulative gain related to swaps | $ 5,000,000 | $ 15,000,000 |
Net Investment Hedge [Member] | Cross Currency Swaps [Member] | Fixed Rate Debt [Member] |  |  |
Derivative [Line Items] |  |  |
Derivative Instruments Frequency of Cash Settlements | semi-annually |  |

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- Definition Accumulated other comprehensive income (loss) cumulative changes in net gain (loss) from net investment hedges net of tax. + References No definition available. + Details
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- Definition Concentration risk credit risk value. + References No definition available. + Details
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- Definition Derivative instruments frequency of cash settlements. + References No definition available. + Details
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- Definition The amount of cash received during the period on settlement of a hedge. + References No definition available. + Details
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- Definition Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as a liability. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (c)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 815 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480237/815-40-50-5 + Details
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- Definition Fair value of all derivative assets designated as hedges of net investment in foreign operations. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 815 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4B -Subparagraph (c)(1) -Publisher FASB -URI https://asc.fasb.org/1943274/2147480434/815-10-50-4B + Details
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- Details
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- Details
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- Details
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