Other Comprehensive Income (Schedule of Items Reclassified out of AOCL) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified									$ (183.0)	$ (138.3)	$ (65.1)
Tax effect									50.7	15.5	18.3
Net of tax	$ (69.4)	$ (6.0)	$ (34.4)	$ (23.8)	$ (51.7)	$ (45.3)	$ (22.3)	$ (4.8)	(133.6)	(124.1)	$ (47.7)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments and Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified									(0.9)	(0.1)
Tax effect									0.3	0.0
Net of tax									(0.6)	(0.1)
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
Tax effect									0.0	0.0
Net of tax									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									5.9	4.4
Tax effect									(2.2)	(1.3)
Net of tax									$ 3.7	$ 3.1