Retirement Benefits (Summary of changes in pension plan assets fair value classified as level 3) (Details) - Level 3 [Member] - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	$ 219.2	$ 210.5
Actual return on plan assets:
Assets held at end of year	12.7	16.5
Assets sold during the period	0.5	1.2
Purchases, sales, and settlements, net	(6.3)	(9.0)
Fair Value at End of Year	226.1	219.2
Pooled Funds [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	9.3	9.4
Actual return on plan assets:
Assets held at end of year	(0.2)	(0.9)
Assets sold during the period	0.5	1.2
Purchases, sales, and settlements, net	(3.0)	(0.4)
Fair Value at End of Year	6.6	9.3
Real Estate [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	150.2	132.8
Actual return on plan assets:
Assets held at end of year	24.0	17.4
Assets sold during the period	0.0	0.0
Purchases, sales, and settlements, net	0.0	0.0
Fair Value at End of Year	174.2	150.2
Insurance Contracts [Member]
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	59.7	68.3
Actual return on plan assets:
Assets held at end of year	(11.1)	0.0
Assets sold during the period	0.0	0.0
Purchases, sales, and settlements, net	(3.3)	(8.6)
Fair Value at End of Year	$ 45.3	$ 59.7