Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5.4	$ 5.8
Interest cost	17.2	22.8
Expected return on plan assets	(48.6)	(47.2)
Prior service cost amortization	0.3	0.3
Actuarial loss amortization	19.7	21.0
Other	0.0	0.0
Net periodic benefit cost	(6.0)	2.7
International
Defined Benefit Plan Disclosure [Line Items]
Service cost	5.7	5.9
Interest cost	6.1	6.2
Expected return on plan assets	(20.2)	(19.5)
Prior service cost amortization	0.0	0.0
Actuarial loss amortization	4.6	4.9
Other	0.3	0.2
Net periodic benefit cost	$ (3.5)	$ (2.3)