Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) - Defined Benefit Pension Plan - USD ($) $ in Millions		3 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Service cost(A)		$ 0.0	$ 1.3
U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost(A)	[1]	6.4	8.3
Interest cost		26.7	24.9
Expected return on plan assets		(50.4)	(52.7)
Prior service cost amortization		0.4	0.6
Actuarial loss amortization		21.7	26.1
Settlements		1.8	0.0
Curtailment		0.0	4.2
Special termination benefits		0.0	1.1
Other		0.0	0.0
Net periodic benefit cost		6.6	12.5
U.S. | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0.0	0.6
U.S. | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		6.6	11.9
International
Defined Benefit Plan Disclosure [Line Items]
Service cost(A)	[1]	6.3	6.7
Interest cost		9.2	7.6
Expected return on plan assets		(20.2)	(18.5)
Prior service cost amortization		0.0	0.0
Actuarial loss amortization		10.0	13.9
Settlements		0.0	(2.3)
Curtailment		0.0	(3.1)
Special termination benefits		0.0	0.4
Other		0.5	2.7
Net periodic benefit cost		5.8	7.4
International | Discontinued Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		0.0	0.7
International | Continuing Operations
Defined Benefit Plan Disclosure [Line Items]
Net periodic benefit cost		$ 5.8	$ 6.7

[1] Includes total service costs from discontinued operations of $1.3 for the three months ended 31 December 2016. There was no discontinued operations activity for the three months ended 31 December 2017.