Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	$ 19.6	$ 23.0	$ 39.3	$ 46.1
Interest cost	43.6	40.0	87.2	80.2
Expected return on plan assets	(54.5)	(56.4)	(109.0)	(113.2)
Amortization:
Prior service credit	(0.7)	(0.7)	(1.4)	(1.3)
Net actuarial loss	24.9	36.1	49.8	72.4
Net periodic benefit cost	32.9	42.0	65.9	84.2
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	0.5	0.6	1.0	1.2
Interest cost	1.6	1.5	3.2	3.1
Amortization:
Prior service credit	(2.7)	(2.7)	(5.2)	(5.4)
Net actuarial loss	0.9	1.1	1.6	2.2
Net periodic benefit cost	$ 0.3	$ 0.5	$ 0.6	$ 1.1