Other (Expense) Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Income and Expenses [Abstract]
Interest income	$ 0.3	$ 0.7	$ 1.1	$ 5.1
Royalty income	2.9	2.1	7.5	6.7
Legacy product liability and environmental charges	(4.0)	(4.1)	(9.4)	(12.5)
Non-operating pension and postretirement benefit cost	(34.3)	(8.6)	(48.3)	(25.9)
Legal settlement (Note 13)	0.0	0.0	70.0	0.0
Other	0.2	10.3	(0.8)	8.2
Other (expense) income	$ (34.9)	$ 0.4	$ 20.1	$ (18.4)