Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits [Member]
Components of net periodic benefit cost (income)
Service cost	$ 22.1	$ 21.7
Interest cost	42.5	42.3
Expected return on plan assets	(54.7)	(56.1)
Amortization:
Prior service credit	(0.7)	(0.7)
Net actuarial loss	31.1	30.0
Net periodic benefit cost (income)	40.3	37.2
Other Postretirement Benefits [Member]
Components of net periodic benefit cost (income)
Service cost	0.3	0.4
Interest cost	0.8	1.0
Amortization:
Prior service credit	(2.8)	(3.7)
Net actuarial loss	0.6	1.2
Net periodic benefit cost (income)	$ (1.1)	$ (1.1)