Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 21.7	$ 19.7
Interest cost	42.3	43.6
Expected return on plan assets	(56.1)	(54.5)
Amortization:
Prior service credit	(0.7)	(0.7)
Net actuarial loss	30.0	24.9
Net periodic benefit cost	37.2	33.0
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	0.4	0.5
Interest cost	1.0	1.6
Amortization:
Prior service credit	(3.7)	(2.5)
Net actuarial loss	1.2	0.7
Net periodic benefit cost	$ (1.1)	$ 0.3