Other (Expense) Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Other Income and Expenses [Abstract]
Interest income	$ 0.5	$ 2.0	$ 0.8	$ 4.4
Royalty income	2.5	2.2	4.6	4.6
Legacy product liability and environmental charges	(0.8)	(5.7)	(5.4)	(8.4)
Non-operating pension and postretirement benefit cost	(7.0)	(8.6)	(14.0)	(17.3)
Legal settlement (Note 13)	0.0	0.0	70.0	0.0
Other	(1.2)	1.0	(1.0)	(2.1)
Other (expense) income	$ (6.0)	$ (9.1)	$ 55.0	$ (18.8)