Other Comprehensive Income (Loss) (Schedule of Changes in AOCL by Component) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Other comprehensive income (loss)
Total Other Comprehensive Income (Loss), net of tax	$ 36.3	$ (22.5)	$ 22.9	$ (20.5)
Accumulated other comprehensive loss
Beginning balance			1,227.2
Net activity	36.3	(22.5)	22.9	(20.5)
Ending balance	1,283.5		1,283.5
Available-for-sale Securities and Hedges [Member]
Other comprehensive income (loss)
Prior to reclassification	(3.5)	(5.5)	13.1	(8.1)
Reclassification from	(0.2)	0.4	(0.9)	0.4
Pre-tax	(3.7)	(5.1)	12.2	(7.7)
Tax effect	1.3	1.8	(4.6)	2.7
Total Other Comprehensive Income (Loss), net of tax	(2.4)	(3.3)	7.6	(5.0)
Accumulated other comprehensive loss
Beginning balance	6.9	(1.7)	(3.1)	0.0
Net activity	(2.4)	(3.3)	7.6	(5.0)
Ending balance	4.5	(5.0)	4.5	(5.0)
Foreign Currency Translation Adjustment [Member]
Other comprehensive income (loss)
Prior to reclassification	37.1	(20.1)	11.6	(17.7)
Reclassification from	1.0	0.0	1.0	0.0
Pre-tax	38.1	(20.1)	12.6	(17.7)
Tax effect	0.0	0.0	0.0	0.0
Total Other Comprehensive Income (Loss), net of tax	38.1	(20.1)	12.6	(17.7)
Accumulated other comprehensive loss
Beginning balance	(140.7)	(90.4)	(115.2)	(92.8)
Net activity	38.1	(20.1)	12.6	(17.7)
Ending balance	(102.6)	(110.5)	(102.6)	(110.5)
Change in Pension and Postretirement Defined Benefit Plans [Member]
Other comprehensive income (loss)
Prior to reclassification	(0.5)	0.0	(0.1)	0.0
Reclassification from	1.5	1.1	4.4	3.2
Pre-tax	1.0	1.1	4.3	3.2
Tax effect	(0.4)	(0.2)	(1.6)	(1.0)
Total Other Comprehensive Income (Loss), net of tax	0.6	0.9	2.7	2.2
Accumulated other comprehensive loss
Beginning balance	(48.7)	(46.7)	(50.8)	(48.0)
Net activity	0.6	0.9	2.7	2.2
Ending balance	(48.1)	(45.8)	(48.1)	(45.8)
Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income (loss)
Prior to reclassification	33.1	(25.6)	24.6	(25.8)
Reclassification from	2.3	1.5	4.5	3.6
Pre-tax	35.4	(24.1)	29.1	(22.2)
Tax effect	0.9	1.6	(6.2)	1.7
Total Other Comprehensive Income (Loss), net of tax	36.3	(22.5)	22.9	(20.5)
Accumulated other comprehensive loss
Beginning balance	(182.5)	(138.8)	(169.1)	(140.8)
Net activity	36.3	(22.5)	22.9	(20.5)
Ending balance	$ (146.2)	$ (161.3)	$ (146.2)	$ (161.3)