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DERIVATIVES AND RISK MANAGEMENT ACTIVITIES Table 2 - Derivative Instruments Eligible for Offset (Details) - Commodity contracts - USD ($)
$ in Thousands
Jun. 30, 2018
Dec. 31, 2017
Derivative Assets and Liabilities Eligible for Offset, Net [Line Items]    
Net amounts of assets presented in the consolidated balance sheets $ 0 $ 0
Net amounts of liabilities presented in the consolidated balance sheets $ (247) $ (878)