Retirement Plans (Schedule of Net Periodic Pension and Postretirement Benefit (Credit) Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Pension plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 2.5	$ 1.9	$ 1.9
Interest cost	$ 18.0	$ 21.1	$ 20.6
Interest cost - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Expected return on plan assets	$ (21.7)	$ (19.5)	$ (21.5)
Expected return on plan assets - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Recognized net actuarial loss (gain)	$ 2.6	$ 1.8	$ 1.7
Recognized net actuarial loss (gain) - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Settlement loss recognized	$ 0.0	$ 0.0	$ (7.9)
Net periodic benefit cost (credit)	1.4	5.3	10.6
Postretirement plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	0.0	0.0	0.0
Interest cost	$ 0.2	$ 0.2	$ 0.2
Interest cost - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Expected return on plan assets	$ 0.0	$ 0.0	$ 0.0
Expected return on plan assets - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Recognized net actuarial loss (gain)	$ (0.2)	$ (0.3)	$ (0.3)
Recognized net actuarial loss (gain) - financial statement location	Nonoperating Income (Expense)	Nonoperating Income (Expense)	Nonoperating Income (Expense)
Settlement loss recognized	$ 0.0	$ 0.0	$ 0.0
Net periodic benefit cost (credit)	$ 0.0	$ (0.1)	$ (0.1)