DERIVATIVE FINANCIAL INSTRUMENTS - Schedule of Commodity Swaps (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Fair value of derivatives - gross presentation, assets (liability)	$ (1,152)	$ 595
Effects of netting arrangements, asset (liability)	0	0
Fair value of derivatives - net presentation, asset (liability)	(1,152)	595
Current assets
Derivative [Line Items]
Fair value of derivatives - gross presentation, assets	7	260
Effects of netting arrangements, asset	(7)	0
Fair value of derivatives - net presentation, asset	0	260
Fair value of derivatives - net presentation, asset (liability)	0	260
Non-current assets
Derivative [Line Items]
Fair value of derivatives - gross presentation, assets	195	978
Effects of netting arrangements, asset	(195)	(643)
Fair value of derivatives - net presentation, asset	0	335
Fair value of derivatives - net presentation, asset (liability)	0	335
Current liabilities
Derivative [Line Items]
Fair value of derivatives - gross presentation, liabilities	(142)	0
Effects of netting arrangements, liability	7	0
Fair value of derivatives - net presentation, liability	(135)	0
Fair value of derivatives - net presentation, asset (liability)	(135)	0
Non-current liabilities
Derivative [Line Items]
Fair value of derivatives - gross presentation, liabilities	(1,212)	(643)
Effects of netting arrangements, liability	195	643
Fair value of derivatives - net presentation, liability	(1,017)	0
Fair value of derivatives - net presentation, asset (liability)	$ (1,017)	$ 0

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, and obligation to return cash collateral under master netting arrangements.

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