Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2010
Amortization:
Prior service credit	$ (12.9)
Net actuarial loss	97.1
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	71.8	70.1	68.7
Interest cost	167.6	163.9	159.7
Expected return on plan assets	(228.1)	(204.5)	(192.1)
Amortization:
Prior service credit	(2.3)	(2.2)	(3.8)
Net transition obligation		0.4	0.4
Net actuarial loss	94.7	63.7	42.1
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements	1.0
Net periodic benefit cost	104.7	91.4	75.0
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	2.2	3.5	3.8
Interest cost	7.2	10.2	12.5
Expected return on plan assets
Amortization:
Prior service credit	(10.6)	(10.6)	(10.6)
Net transition obligation
Net actuarial loss	2.4	6.4	8.4
Net periodic benefit cost	$ 1.2	$ 9.5	$ 14.1