DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Location and Fair Value Amounts of Derivative Instruments Reported in Balance Sheet (Details) $ in Millions	Sep. 30, 2017 USD ($)
Asset Derivatives
Derivative contracts	$ 3.6
Liability Derivatives
Derivative contracts, liabilities	0.5
Not Designated as Hedging Instrument | Commodity contracts
Asset Derivatives
Derivative contracts	3.6
Liability Derivatives
Derivative contracts, liabilities	0.5
Not Designated as Hedging Instrument | Commodity contracts | Current assets: Fair value of derivative contracts
Asset Derivatives
Derivative contracts	2.6
Not Designated as Hedging Instrument | Commodity contracts | Long-term assets: Fair value of derivative contracts
Asset Derivatives
Derivative contracts	1.0
Not Designated as Hedging Instrument | Commodity contracts | Current liabilities: Fair value of derivative contracts
Liability Derivatives
Derivative contracts, liabilities	0.4
Not Designated as Hedging Instrument | Commodity contracts | Long-term liabilities: Fair value of derivative contracts
Liability Derivatives
Derivative contracts, liabilities	$ 0.1