Other Comprehensive Income (Loss) (Schedule of Changes in AOCL by Component) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income (loss)
Total Other Comprehensive Loss, net of tax	$ (28.0)	$ (9.4)
Accumulated other comprehensive loss
Beginning balance	1,227.2
Net activity	(28.0)	(9.4)
Ending balance	1,187.0
Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Prior to reclassification	16.2	0.2
Reclassification from	(0.2)	0.0
Pre-tax	16.0	0.2
Tax effect	(5.8)	(0.1)
Total Other Comprehensive Loss, net of tax	10.2	0.1
Accumulated other comprehensive loss
Beginning balance	(3.1)	0.0
Net activity	10.2	0.1
Ending balance	7.1	0.1
Foreign Currency Translation Adjustment [Member]
Other comprehensive income (loss)
Prior to reclassification	(39.5)	(10.2)
Reclassification from	0.0	0.0
Pre-tax	(39.5)	(10.2)
Tax effect	0.0	0.0
Total Other Comprehensive Loss, net of tax	(39.5)	(10.2)
Accumulated other comprehensive loss
Beginning balance	(115.2)	(92.8)
Net activity	(39.5)	(10.2)
Ending balance	(154.7)	(103.0)
Change in Pension and Postretirement Defined Benefit Plans [Member]
Other comprehensive income (loss)
Prior to reclassification	0.4	0.0
Reclassification from	1.5	1.1
Pre-tax	1.9	1.1
Tax effect	(0.6)	(0.4)
Total Other Comprehensive Loss, net of tax	1.3	0.7
Accumulated other comprehensive loss
Beginning balance	(50.8)	(48.0)
Net activity	1.3	0.7
Ending balance	(49.5)	(47.3)
Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income (loss)
Prior to reclassification	(22.9)	(10.0)
Reclassification from	1.3	1.1
Pre-tax	(21.6)	(8.9)
Tax effect	(6.4)	(0.5)
Total Other Comprehensive Loss, net of tax	(28.0)	(9.4)
Accumulated other comprehensive loss
Beginning balance	(169.1)	(140.8)
Net activity	(28.0)	(9.4)
Ending balance	$ (197.1)	$ (150.2)