FAIR VALUE MEASUREMENTS (Schedule of Assets and Liabilities Measured on a Recurring Basis) (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Commodity futures instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	$ 4,822	$ 301
Derivative liabilities	(517)	(296)
Commodity futures instruments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	4,822	301
Derivative liabilities	(517)	(296)
Commodity options instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		421
Derivative liabilities	(11,279)	(3,551)
Commodity options instruments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets		421
Derivative liabilities	(11,279)	(3,551)
Foreign currency instruments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	430	45
Derivative liabilities	(1,943)	(211)
Foreign currency instruments | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	430	45
Derivative liabilities	$ (1,943)	$ (211)