Retirement Plans (Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Retirement Benefits [Abstract]
Service cost	$ 0.6	$ 0.8	$ 1.3
Interest cost	13.9	13.9	9.8
Expected return on plan assets	(13.0)	(13.9)	(15.4)
Amortization of net loss (gain)	3.1	3.7	1.7
Pension expense (benefit) other than service	4.0	3.7	(3.9)
Net periodic cost (benefit)	$ 4.6	$ 4.5	$ (2.6)

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of expense (reversal of expense) for net periodic benefit cost components, excluding service cost component, of defined benefit plan. Amount includes, but is not limited to, interest cost, expected (return) loss on plan asset, amortization of prior service cost (credit), amortization of (gain) loss, amortization of transition (asset) obligation, settlement (gain) loss, curtailment (gain) loss and certain termination benefits.

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