FINANCIAL DERIVATIVE INSTRUMENTS - Summary of Gain or Loss Recognized in AOCI (Details) - Commodity swap contracts - Cash Flow Hedging - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion, net of tax)			$ (1,501)
Amount of Gain (Loss) Recognized in AOCI on Derivatives (Effective Portion, net of tax)					$ (765)
Amount of Gain (Loss) Reclassified from AOCI into Earnings	$ (478)	$ 0	$ (646)	$ 0

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Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

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-Publisher FASB
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-Topic 220
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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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