INFORMATION BY OPERATING SEGMENT - Reconciliation of Consolidated Net Economic Earnings to Consolidated Net Income (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting [Abstract]
Net Income	$ 116.0	$ 45.2
Unrealized loss on energy-related derivative contracts	0.8	3.8
Lower of cost or market inventory adjustments	0.0	(0.1)
Realized gain on economic hedges prior to sale of the physical commodity	(0.1)	(0.1)
Acquisition, divestiture and restructuring activities	1.7	0.1
Income tax effect of adjustments	(0.6)	(1.4)
Effects of the Tax Cuts and Jobs Act	(59.9)	0.0
Net Economic Earnings	$ 57.9	$ 47.5