Fair Value Measurements - Fair Value of Debt (Details) - USD ($) $ in Millions	Mar. 31, 2025	Sep. 30, 2024
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Unamortized discounts and issuance costs	$ (6.8)	$ (5.6)
Level 2 \| Fair value \| Senior Notes \| 2031 Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	465.6	478.5
Level 2 \| Carrying Value \| Senior Notes \| 2031 Notes
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	530.7	530.4
Unamortized discounts and issuance costs	$ (4.3)	$ (4.6)

Amount of unamortized debt discount (premium) and debt issuance costs.

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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details