INFORMATION BY OPERATING SEGMENT - Reconciliation of Consolidated Net Income to Consolidated Net Economic Earnings (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting [Abstract]
Net income	$ (14.9)	$ 11.7	$ 52.2	$ 35.6	$ (9.6)	$ 6.6	$ 30.2	$ 25.6	$ 84.6	$ 52.8	$ 62.6
Unrealized loss (gain) on energy-related derivatives									(0.9)	0.5	(0.3)
Lower of cost or market inventory adjustments									(0.7)	0.9	0
Realized (gain) loss on economic hedges prior to the sale of the physical commodity									(0.2)	0	0.2
Acquisition, divestiture and restructuring activities									17.3	10.8	0.1
Net Economic Earnings (Non-GAAP)									$ 100.1	$ 65.0	$ 62.6