Supplemental Financial Statement Information (Supplemental Statement of Income Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Financial Statement Related Disclosures [Abstract]
Interest income	$ (0.6)	$ (7.7)	$ (1.4)
Interest income on restricted cash	0.0	(5.8)	(5.2)
Foreign currency exchange loss	8.7	5.2	8.1
Pension expense other than service costs	(1.7)	(2.3)	(6.3)
Settlement loss on pension plan terminations	0.0	3.7	14.1
Acquisition foreign currency gains	2.2	(13.6)	(15.2)
Pre-acquisition insurance proceeds	(4.9)	0.0	0.0
Settlement of acquired business hedging contracts	0.0	1.5	0.0
Gain on sale of assets (1)	(1.0)	0.0	0.0
Transition services agreement income	0.9	(1.4)	0.0
Other	0.2	6.1	(0.7)
Other items, net	$ 2.0	$ (14.3)	$ (6.6)