Share-Based Payments - Narrative (Details) - USD ($) shares in Millions, $ in Millions	12 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Compensation expense under defined contribution plans	$ 26.0	$ 24.7	$ 23.1
Compensation expense related to share-based payments	61.4	61.5	$ 45.9
Unrecognized compensation expense	$ 106.7	$ 68.7
Recognition period of unrecognized compensation expense (in years)	3 years	3 years
Performance Shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period (in years)	3 years
2020 Stock Incentive Plan
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Securities available for future issuance (in shares)	11.3
2020 Stock Incentive Plan \| Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expiration term of unexercised options (in years)	7 years

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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