Retirement Benefits (Schedule of Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014
US [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 10.6	$ 10.6	$ 21.2	$ 21.3
Interest cost	31.3	32.7	62.5	65.4
Expected return on plan assets	(50.5)	(46.9)	(101.0)	(93.9)
Actuarial loss amortization	19.6	19.6	39.4	39.2
Prior service cost amortization	0.7	0.7	1.4	1.4
Settlement and curtailment charges	15.7	0	15.6	0
Special termination benefits	2.1	0	4.8	0.2
Other	0	0	1.1	0
Net periodic benefit cost	29.5	16.7	45.0	33.6
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7.9	9.0	16.1	17.8
Interest cost	14.2	16.9	29.2	33.5
Expected return on plan assets	(19.1)	(19.6)	(40.2)	(38.8)
Actuarial loss amortization	10.1	8.9	20.6	17.7
Prior service cost amortization	0.1	0	0.1	0.1
Settlement and curtailment charges	0	0.5	(0.1)	0.5
Special termination benefits	0.9	0	0.9	0
Other	0.5	0.5	1.0	1.0
Net periodic benefit cost	14.6	16.2	27.6	31.8
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	0.7	0.8	1.4	1.6
Interest cost	0.5	0.6	1.1	1.2
Expected return on plan assets	0	0	0	0
Actuarial loss amortization	0.2	0.5	0.4	0.9
Prior service cost amortization	0	0	0	0
Other	0	0	0	0
Net periodic benefit cost	$ 1.4	$ 1.9	$ 2.9	$ 3.7