Business Segment Information (Reconciliation of Operating Income) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2017
Segment Reporting Information [Line Items]
Business separation costs	$ 0.0	$ 0.0	$ 0.0	$ (32.5)
Cost reduction and asset actions	0.0	(42.7)	0.0	(103.0)	$ (151.4)
Goodwill and intangible asset impairment charge	0.0	(162.1)	0.0	(162.1)
Operating Income	515.8	258.7	1,431.9	982.6
Segment Reconciling Items
Segment Reporting Information [Line Items]
Business separation costs	0.0	0.0	0.0	(32.5)
Cost reduction and asset actions	0.0	(42.7)	0.0	(103.0)
Goodwill and intangible asset impairment charge	0.0	(162.1)	0.0	(162.1)
Segment Total
Segment Reporting Information [Line Items]
Operating Income	$ 515.8	$ 463.5	$ 1,431.9	$ 1,280.2