Business Segment Information (Reconciliation of Operating Income) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Segment Reporting Information [Line Items]
Business separation costs	$ 0.0	$ (7.4)	$ (30.2)	$ (19.4)
Cost reduction and asset actions	(10.3)	(10.7)	(60.3)	(10.7)
Pension settlement loss	(4.1)	(2.0)	(4.1)	(2.0)
Operating Income	391.2	371.6	719.3	744.1
Operating Segments [Member]
Segment Reporting Information [Line Items]
Operating Income	405.6	391.7	813.9	776.2
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Business separation costs	0.0	(7.4)	(30.2)	(19.4)
Cost reduction and asset actions	(10.3)	(10.7)	(60.3)	(10.7)
Pension settlement loss	$ (4.1)	$ (2.0)	$ (4.1)	$ (2.0)