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Intangible Assets - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Intangible Asset, Acquired, Finite-Lived [Line Items]
Impairment of intangible assets, finite-lived	$ 16.2
Impairment of intangible assets, finite-lived Extensible Enumeration	amortized intangible assets
Amortization of intangible assets	$ 9.5	$ 7.5	$ 14.7
Client base
Intangible Asset, Acquired, Finite-Lived [Line Items]
Finite-lived intangible assets acquired	420.9
Impairment of intangible assets, finite-lived		27.8
Client base | CDI
Intangible Asset, Acquired, Finite-Lived [Line Items]
Finite-lived intangible assets acquired		$ 3.6
Trade/domain names and other licenses
Intangible Asset, Acquired, Finite-Lived [Line Items]
Finite-lived intangible assets acquired	$ 6.5

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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.

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