Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service costs	$ 0.5	$ 0.5	$ 1.0	$ 1.1
Interest costs	0.1	0.1	0.3	0.3
Expected return on plan assets	(0.2)	(0.2)	(0.4)	(0.3)
Amortization of net loss	0.8	0.9	1.5	1.3
Net periodic pension (benefit) cost	1.2	1.3	2.4	2.4
United States
Defined Benefit Plan Disclosure [Line Items]
Service costs	0.1	0.3	0.3	0.7
Interest costs	1.4	2.0	2.9	4.0
Expected return on plan assets	(2.7)	(3.2)	(5.4)	(6.4)
Amortization of net loss	0.6	1.2	1.1	2.4
Net periodic pension (benefit) cost	$ (0.6)	$ 0.3	$ (1.1)	$ 0.7