Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Amortization:
Prior service credit	$ (12.9)
Net actuarial loss	102.6
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	78.5	92.1	71.8
Interest cost	174.2	160.2	167.6
Expected return on plan assets	(217.9)	(226.3)	(228.1)
Amortization:
Prior service credit	(2.7)	(2.5)	(2.3)
Net actuarial loss	99.7	144.6	94.7
Settlements	(0.1)	0	1.0
Net periodic benefit cost	131.7	168.1	104.7
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	2.0	2.3	2.2
Interest cost	6.5	6.3	7.2
Expected return on plan assets
Amortization:
Prior service credit	(10.2)	(10.7)	(10.6)
Net actuarial loss	2.9	4.4	2.4
Settlements
Net periodic benefit cost	$ 1.2	$ 2.3	$ 1.2