DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Location and Fair Value Amounts of Derivative Instruments Reported in Balance Sheet (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Asset Derivatives
Fair value of derivative instruments, assets	$ 38,576
Designated as Hedging Instrument | Commodity contracts
Asset Derivatives
Fair value of derivative instruments, assets	38,576
Liability Derivatives
Fair value of derivative instruments, liabilities	0
Designated as Hedging Instrument | Commodity contracts | Current asset
Asset Derivatives
Fair value of derivative instruments, assets	38,576
Designated as Hedging Instrument | Commodity contracts | Long-term assets
Asset Derivatives
Fair value of derivative instruments, assets	0
Designated as Hedging Instrument | Commodity contracts | Current liabilities
Liability Derivatives
Fair value of derivative instruments, liabilities	0
Designated as Hedging Instrument | Commodity contracts | Long-term liabilities
Liability Derivatives
Fair value of derivative instruments, liabilities	$ 0