Other Comprehensive Income (Schedule of Changes in AOCL by Component) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Prior to reclassification	$ 67.7	$ (35.8)
Reclassification from	6.0	4.3
Pre-tax	73.7	(31.5)
Tax effect	(14.6)	3.2	$ 5.1
Total Other Comprehensive Income (Loss), Net of Tax	59.1	(28.3)	(66.7)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	1,227.2
Net activity	59.1	(28.3)	(66.7)
Ending balance	1,358.2	1,227.2
Derivative Instruments and Hedges [Member]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Prior to reclassification	12.7	(4.9)
Reclassification from	(0.9)	(0.1)
Pre-tax	11.8	(5.0)
Tax effect	(4.4)	1.9
Total Other Comprehensive Income (Loss), Net of Tax	7.4	(3.1)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3.1)	0.0
Net activity	7.4	(3.1)
Ending balance	4.3	(3.1)	0.0
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Prior to reclassification	32.9	(22.4)
Reclassification from	1.0	0.0
Pre-tax	33.9	(22.4)
Tax effect	0.0	0.0
Total Other Comprehensive Income (Loss), Net of Tax	33.9	(22.4)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(115.2)	(92.8)
Net activity	33.9	(22.4)
Ending balance	(81.3)	(115.2)	(92.8)
Change in Pension and Postretiremen Defined Benefit Plans [Member]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Prior to reclassification	22.1	(8.5)
Reclassification from	5.9	4.4
Pre-tax	28.0	(4.1)
Tax effect	(10.2)	1.3
Total Other Comprehensive Income (Loss), Net of Tax	17.8	(2.8)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(50.8)	(48.0)
Net activity	17.8	(2.8)
Ending balance	(33.0)	(50.8)	(48.0)
AOCI Attributable to Parent [Member]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Total Other Comprehensive Income (Loss), Net of Tax	59.1	(28.3)	(66.7)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(169.1)	(140.8)
Net activity	59.1	(28.3)	(66.7)
Ending balance	$ (110.0)	$ (169.1)	$ (140.8)