Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended					12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ 0.0	$ 0.0	$ 5.0	$ 0.0			$ 5.0
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Settlements					$ 43.7	$ (5.0)	(6.2)	$ (5.2)
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost						23.4	21.4	25.5
Interest cost						91.2	113.4	107.2
Expected return on plan assets						(188.7)	(172.5)	(201.6)
Prior service cost amortization						1.2	1.1	1.6
Actuarial loss amortization						83.7	65.3	87.4
Settlements						5.0	6.2	45.0
Special termination benefits						0.0	0.7	0.4
Other						0.0	0.0	0.0
Net Periodic (Benefit) Cost						15.8	35.6	65.5
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Service cost						23.3	19.3	25.5
Interest cost						24.8	35.8	37.3
Expected return on plan assets						(77.4)	(75.1)	(81.7)
Prior service cost amortization						0.0	0.0	0.0
Actuarial loss amortization						19.5	10.9	40.2
Settlements						0.2	0.2	3.5
Special termination benefits						0.0	0.1	0.0
Other						0.8	0.8	1.5
Net Periodic (Benefit) Cost						$ (8.8)	$ (8.0)	$ 26.3