Fair Value, Not Measured at Fair Value (Detail) - USD ($) $ in Millions |
Mar. 31, 2026 |
Sep. 30, 2025 |
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| Estimate of Fair Value Measurement | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Cash and Cash Equivalents, Fair Value Disclosure | $ 362.2 | $ 379.2 |
| Long-term Debt, Fair Value | 791.9 | 818.8 |
| Cash and cash equivalents | 362.2 | 379.2 |
| Debt | 793.5 | 802.7 |
| Level 1 | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Cash and Cash Equivalents, Fair Value Disclosure | 362.2 | 379.2 |
| Long-term Debt, Fair Value | 0.0 | 0.0 |
| Level 2 | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Cash and Cash Equivalents, Fair Value Disclosure | 0.0 | 0.0 |
| Long-term Debt, Fair Value | 791.9 | 808.9 |
| Level 3 | ||
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | ||
| Cash and Cash Equivalents, Fair Value Disclosure | 0.0 | 0.0 |
| Long-term Debt, Fair Value | $ 0.0 | $ 9.9 |
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- Definition Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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- Definition Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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