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Derivative Financial Instruments and Fair Value Measurements (Tables) | 9 Months Ended
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Jun. 30, 2025
Derivative Financial Instruments and Fair Value Measurements [Abstract] |
Schedule of Notional Principle, Fixed Rates and Expiration Dates of Outstanding Interest Rate Swap Agreements | The notional principal, fixed rates and related effective and expiration dates of the Company’s outstanding interest rate swap agreements were as follows:
June 30, 2025
Notional Amount Currency |  | Notional Amount (in millions) |  | Fixed Rate |  | Effective Date |  | Expiration Date
USD |  | 400.0 |  | 1.283% |  | February 2023 |  | March 2028
September 30, 2024
Notional Amount Currency |  | Notional Amount (in millions) |  | Fixed Rate |  | Effective Date |  | Expiration Date
USD |  | 400.0 |  | 1.283% |  | February 2023 |  | March 2028
Schedule of Financial Assets and Liabilities Recorded at Fair Value on a Recurring Basis | Below are the Company's non-pension financial assets and liabilities recorded at fair value on a recurring basis within the ASC 820-10 fair value hierarchy:
| June 30, 2025
| Balance Sheet Location |  | Quoted Prices in Active Markets for Identical Assets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total Fair Value
Interest rate contracts | Other current assets |  | $ | — |  |  | $ | 9.5 |  |  | $ | — |  |  | $ | 9.5 |
Interest rate contracts | Other non-current assets |  | — |  |  | 12.9 |  |  | — |  |  | 12.9 |
Interest rate contracts | Other current liabilities |  | — |  |  | (0.9) |  |  | — |  |  | (0.9) |
Interest rate contracts | Other long-term liabilities |  | — |  |  | (2.7) |  |  | — |  |  | (2.7) |
Credit facility investment | Other non-current assets |  | — |  |  | — |  |  | 5.4 |  |  | 5.4 |
Equity investment | Other non-current assets |  | 13.2 |  |  | — |  |  | — |  |  | 13.2 |
Total net assets at fair value |  | $ | 13.2 |  |  | $ | 18.8 |  |  | $ | 5.4 |  |  | $ | 37.4 |
| September 30, 2024
| Balance Sheet Location |  | Quoted Prices in Active Markets for Identical Assets (Level 1) |  | Significant Observable Inputs (Level 2) |  | Significant Unobservable Inputs (Level 3) |  | Total Fair Value
Interest rate contracts | Other current assets |  | $ | — |  |  | $ | 9.2 |  |  | $ | — |  |  | $ | 9.2 |
Interest rate contracts | Other non-current assets |  | — |  |  | 16.5 |  |  | — |  |  | 16.5 |
Interest rate contracts | Other current liabilities |  | — |  |  | (0.9) |  |  | — |  |  | (0.9) |
Interest rate contracts | Other long-term liabilities |  | — |  |  | (3.6) |  |  | — |  |  | (3.6) |
Credit facility investment | Other non-current assets |  | — |  |  | — |  |  | 21.9 |  |  | 21.9 |
Equity investment | Other non-current assets |  | 19.4 |  |  | — |  |  | — |  |  | 19.4 |
Total net assets at fair value |  | $ | 19.4 |  |  | $ | 21.2 |  |  | $ | 21.9 |  |  | $ | 62.5 |
Schedule of Changes in Fair Value of Level 3 Investment Assets | The table below sets forth a summary of changes in the fair value of the Company's Level 3 investment assets:
|  | Nine Months Ended June 30, 2025
|  | Beginning Balance |  | Investment Gains/(Losses) |  | Interest Earned |  | Loans |  | Collections |  | Ending Balance
Credit facility investment including accrued interest | $ | 21.9 |  |  | (0.7) |  |  | 0.8 |  |  | 8.0 |  |  | (24.6) |  |  | $ | 5.4 |

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- Definition Disclosure information pertaining to derivative instruments and fair value measurements. + References No definition available. + Details
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- Definition Tabular disclosure of the notional amounts, fixed rates and related expiration dates of outstanding derivative positions. + References No definition available. + Details
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- Definition Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 55 -Paragraph 101 -Publisher FASB -URI https://asc.fasb.org/1943274/2147482078/820-10-55-101 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 3 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-3 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 820 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 2 -Subparagraph (c) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482106/820-10-50-2 + Details
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