Retirement Benefits (Details) (USD $) In Millions	12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2009
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 70.1	$ 68.7	$ 56.0
Interest cost	163.9	159.7	154.7
Expected return on plan assets	(204.5)	(192.1)	(191.5)
Amortization:
Prior service credit	(2.2)	(3.8)	(3.7)
Net transition obligation	0.4	0.4	0.3
Net actuarial loss	63.7	42.1	16.9
Net periodic benefit cost	91.4	75.0	32.7
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	3.5	3.8	3.6
Interest cost	10.2	12.5	13.3
Amortization:
Prior service credit	(10.6)	(10.6)	(10.6)
Net actuarial loss	6.4	8.4	9.5
Net periodic benefit cost	$ 9.5	$ 14.1	$ 15.8