Retirement Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Amortization:
Prior service credit	$ (17.2)
Net actuarial loss	123.2
Pension Benefits [Member]
Components of net periodic benefit cost
Service cost	85.7	$ 78.5	$ 92.1
Interest cost	167.2	174.2	160.2
Expected return on plan assets	(223.2)	(217.9)	(226.3)
Amortization:
Prior service credit	(2.7)	(2.7)	(2.5)
Net actuarial loss	118.7	99.7	144.6
Settlements	0.0	(0.1)	0.0
Net periodic benefit cost (income)	145.7	131.7	168.1
Other Postretirement Benefits [Member]
Components of net periodic benefit cost
Service cost	1.5	2.0	2.3
Interest cost	4.1	6.5	6.3
Amortization:
Prior service credit	(14.5)	(10.2)	(10.7)
Net actuarial loss	4.5	2.9	4.4
Net periodic benefit cost (income)	$ (4.4)	$ 1.2	$ 2.3