Pension Plans (Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan) (Details) - Pension Plan - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
United States
Change in Projected Benefit Obligation
Benefit obligation at beginning of year		$ 254.6	$ 383.4
Service cost		0.0	0.0	$ 0.0
Interest cost		14.5	19.9	12.7
Actuarial loss/(gain)		15.4	0.2
Benefits paid		(24.9)	(28.7)
Expenses paid		0.0	0.0
Plan settlements	$ (120.2)	0.0
Foreign currency exchange rate changes		0.0	0.0
Projected Benefit Obligation at end of year	254.6	259.6	254.6	383.4
Change in Plan Assets
Estimated fair value of plan assets at beginning of year		222.2	356.9
Actual return on plan assets		38.3	11.8
Company contributions		2.5	2.4
Plan settlements		0.0	(120.2)
Benefits paid		(24.9)	(28.7)
Expenses paid		0.0	0.0
Foreign currency exchange rate changes		0.0	0.0
Estimated fair value of plan assets at end of year	222.2	238.1	222.2	356.9
Funded status at end of year	(32.4)	(21.5)	(32.4)
International
Change in Projected Benefit Obligation
Benefit obligation at beginning of year		89.8	84.8
Service cost		0.4	0.3	0.6
Interest cost		3.8	3.6	1.8
Actuarial loss/(gain)		15.3	(0.6)
Benefits paid		(5.1)	(5.6)
Expenses paid		(0.7)	0.0
Plan settlements		0.0	0.0
Foreign currency exchange rate changes		7.7	7.3
Projected Benefit Obligation at end of year	89.8	111.2	89.8	84.8
Change in Plan Assets
Estimated fair value of plan assets at beginning of year		83.4	78.3
Actual return on plan assets		5.3	0.7
Company contributions		4.4	3.4
Plan settlements		0.0	0.0
Benefits paid		(5.1)	(5.6)
Expenses paid		(0.7)	0.0
Foreign currency exchange rate changes		7.5	6.6
Estimated fair value of plan assets at end of year	83.4	94.8	83.4	$ 78.3
Funded status at end of year	$ (6.4)	$ (16.4)	$ (6.4)