Other Comprehensive Income (Loss) (Schedule of Items Reclassified out of AOCL) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amount reclassified	$ (35.3)	$ (5.8)
Tax effect	11.8	1.5
Net of tax	(23.8)	(4.8)
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)	0.0
Tax effect	0.1	0.0
Net of tax	(0.1)	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
Tax effect	(0.5)	(0.4)
Net of tax	$ 1.0	$ 0.7