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ASSET RETIREMENT OBLIGATIONS AND RESTRICTED CASH - Schedule of Change in Asset Retirement Obligation (Details) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Dec. 31, 2016
Jun. 30, 2017
Dec. 31, 2016
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]              
Asset retirement obligation, beginning of period     $ 17,033 $ 8,573 $ 8,573    
Revision of estimate     0   4,186    
Acquired in asset acquisitions or business combinations     0   5,454    
Accretion of liabilities $ 346 $ 176 691 351 906    
Settlements     (542)   (2,086)    
Asset retirement obligation, end of period 17,182   17,182   17,033    
Asset Retirement Obligation [Abstract]              
Current           $ 32 $ 32
Non-current           17,150 17,001
Asset retirement obligation, end of period $ 17,182   $ 17,033 $ 8,573 $ 8,573 $ 17,182 $ 17,033