Other Comprehensive Income (Loss) (Schedule of Items Reclassified out of AOCL) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	$ (16.1)	$ (35.3)	$ (92.7)	$ (69.2)
Tax effect	10.4	(9.7)	29.5	(2.2)
Net of tax	(6.0)	(45.3)	(64.2)	(72.4)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-sale Securities and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	(0.2)	0.4	(0.9)	0.4
Tax effect	0.0	(0.2)	0.2	(0.2)
Net of tax	(0.2)	0.2	(0.7)	0.2
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	1.0	0.0	1.0	0.0
Tax effect	0.0	0.0	0.0	0.0
Net of tax	1.0	0.0	1.0	0.0
Reclassification out of Accumulated Other Comprehensive Income [Member] | Change in Pension and Postretirement Defined Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	1.5	1.1	4.4	3.2
Tax effect	(0.5)	(0.2)	(1.6)	(1.0)
Net of tax	$ 1.0	$ 0.9	$ 2.8	$ 2.2