Retirement Benefits (Changes recognized in other comprehensive income on pretax basis) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
US [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during the period	$ 351.8	$ 11.5
Amortization of net actuarial loss	(97.8)	(83.1)
Prior service cost (credit) arising during the period	1.2	0.9
Amortization of prior service cost	(2.8)	(2.9)
Total	252.4	(73.6)
International [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during the period	79.4	92.9
Amortization of net actuarial loss	(43.3)	(36.8)
Prior service cost (credit) arising during the period	(3.1)	(0.1)
Amortization of prior service cost	0.0	(0.2)
Total	33.0	55.8
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss arising during the period	(2.3)	(3.0)
Amortization of net actuarial loss	(0.8)	(1.7)
Total	$ (3.1)	$ (4.7)