Retirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Pension Benefits [Member]
Components of net periodic benefit cost (income)
Service cost	$ 21.8	$ 21.5	$ 43.9	$ 43.2
Interest cost	42.2	41.6	84.7	83.9
Expected return on plan assets	(54.4)	(55.8)	(109.1)	(111.9)
Amortization:
Prior service credit	(0.7)	(0.6)	(1.4)	(1.3)
Net actuarial loss	31.1	29.6	62.2	59.6
Net periodic benefit cost (income)	40.0	36.3	80.3	73.5
Other Postretirement Benefits [Member]
Components of net periodic benefit cost (income)
Service cost	0.3	0.4	0.6	0.8
Interest cost	0.9	1.1	1.7	2.1
Amortization:
Prior service credit	(2.9)	(3.7)	(5.7)	(7.4)
Net actuarial loss	0.7	1.1	1.3	2.3
Net periodic benefit cost (income)	$ (1.0)	$ (1.1)	$ (2.1)	$ (2.2)