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	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ 0.0	$ 0.0	$ 5.0	$ 0.0	$ 43.7	$ 0.0	$ 0.0	$ 0.0	$ 5.0	$ 43.7
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Settlements					$ 43.7				(6.2)	(5.2)	$ 10.5
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost									21.4	25.5	29.0
Interest cost									113.4	107.2	107.5
Expected return on plan assets									(172.5)	(201.6)	(207.7)
Net actuarial loss amortization									65.3	87.4	88.7
Prior service cost (credit)									1.1	1.6	2.3
Settlements									6.2	45.0	10.5
Curtailments									0.0	0.0	4.3
Special termination benefits									0.7	0.4	2.8
Other									0.0	0.0	0.0
Net periodic benefit cost									35.6	65.5	37.4
Defined Benefit Pension Plan | U.S. | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost									0.0	0.0	(0.7)
Defined Benefit Pension Plan | U.S. | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost									35.6	65.5	36.7
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Service cost									19.3	25.5	25.9
Interest cost									35.8	37.3	32.2
Expected return on plan assets									(75.1)	(81.7)	(75.2)
Net actuarial loss amortization									10.9	40.2	54.7
Prior service cost (credit)									0.0	0.0	(0.1)
Settlements									0.2	3.5	1.7
Curtailments									0.0	0.0	(1.3)
Special termination benefits									0.1	0.0	0.4
Other									0.8	1.5	1.1
Net periodic benefit cost									(8.0)	26.3	39.4
Defined Benefit Pension Plan | International | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost									0.0	0.0	(4.1)
Defined Benefit Pension Plan | International | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost									$ (8.0)	$ 26.3	$ 35.3