Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2018		Sep. 30, 2017		Sep. 30, 2016
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ 43.7	$ 48.5	[1]	$ 10.5	[1]	$ 5.1	[1]
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Settlements	$ 43.7			10.5		5.1
Defined Benefit Pension Plan | U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost		25.5		29.0		36.5
Interest cost		107.2		107.5		110.7
Expected return on plan assets		(201.6)		(207.7)		(202.0)
Net actuarial loss amortization		87.4		88.7		85.3
Prior service cost (credit)		1.6		2.3		2.8
Settlements		45.0		10.5		5.1
Curtailments		0.0		4.3		0.0
Special termination benefits		0.4		2.8		2.0
Other		0.0		0.0		(0.3)
Net periodic benefit cost		65.5		37.4		40.1
Defined Benefit Pension Plan | U.S. | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0.0		(0.7)		(7.9)
Defined Benefit Pension Plan | U.S. | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		65.5		36.7		32.2
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Service cost		25.5		25.9		24.3
Interest cost		37.3		32.2		44.3
Expected return on plan assets		(81.7)		(75.2)		(78.3)
Net actuarial loss amortization		40.2		54.7		35.6
Prior service cost (credit)		0.0		(0.1)		(0.2)
Settlements		3.5		1.7		1.3
Curtailments		0.0		(1.3)		(1.1)
Special termination benefits		0.0		0.4		0.0
Other		1.5		1.1		2.1
Net periodic benefit cost		26.3		39.4		28.0
Defined Benefit Pension Plan | International | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0.0		(4.1)		(4.4)
Defined Benefit Pension Plan | International | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		$ 26.3		$ 35.3		$ 23.6

[1] Fiscal year 2018 includes a loss of $43.7 that primarily resulted from the transfer of certain pension payment obligations to an insurer through the purchase of an irrevocable, nonparticipating group annuity contract during the fourth quarter.