Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Amortization:
Prior service credit	$ (13.2)
Net actuarial loss	149.0
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	92.1	71.8	70.1
Interest cost	160.2	167.6	163.9
Expected return on plan assets	(226.3)	(228.1)	(204.5)
Amortization:
Prior service credit	(2.5)	(2.3)	(2.2)
Net transition obligation	0	0	0.4
Net actuarial loss	144.6	94.7	63.7
Settlements	0	1.0	0
Net periodic benefit cost	168.1	104.7	91.4
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	2.3	2.2	3.5
Interest cost	6.3	7.2	10.2
Expected return on plan assets
Amortization:
Prior service credit	(10.7)	(10.6)	(10.6)
Net transition obligation
Net actuarial loss	4.4	2.4	6.4
Settlements
Net periodic benefit cost	$ 2.3	$ 1.2	$ 9.5