Income Taxes - Schedule of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Unrecognized tax benefits, excluding interest and penalties
Gross unrecognized tax benefits balance at beginning of year	$ 25.0	$ 10.0	$ 4.0
Additions based on tax positions related to the current year	5.0	5.0	4.0
Additions based on tax positions related to prior years	2.0	10.0	3.0
Reductions related to settlements with taxing authorities	(1.0)	0.0	(1.0)
Reductions related to lapses of statute of limitations	(2.0)	0.0
Gross unrecognized tax benefits balance at end of year	$ 29.0	$ 25.0	$ 10.0

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 217
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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Amount of decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of decrease in unrecognized tax benefits resulting from lapses of applicable statutes of limitations.

+ References

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