Quarterly report pursuant to Section 13 or 15(d)

FAIR VALUE MEASUREMENTS (Details)

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FAIR VALUE MEASUREMENTS (Details) - USD ($)
$ in Thousands
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Liabilities:      
Asset retirement obligation capitalized $ 1,468 $ 11,557  
Level 1      
Assets:      
Derivative Instruments 0   $ 0
Liabilities:      
Derivative Instruments 0   0
Level 2      
Assets:      
Derivative Instruments 23,339   87,532
Liabilities:      
Derivative Instruments 77,702   35,523
Level 3      
Assets:      
Derivative Instruments 0   0
Liabilities:      
Derivative Instruments $ 0   $ 0