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Derivative Instruments (Details 2) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2020
Jun. 30, 2019
Jun. 30, 2020
Jun. 30, 2019
Energy contracts and options [Member] | Cost of revenues [Member]        
Effects of derivative instruments on the consolidated statements of operations        
Amount of Gain (Loss) Recognized on Derivatives $ (6,200) $ (7,921) $ (18,589) $ (10,830)