Quarterly report pursuant to Section 13 or 15(d)

PROPERTY AND EQUIPMENT (Schedule of Asset Retirement Obligation) (Details)

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PROPERTY AND EQUIPMENT (Schedule of Asset Retirement Obligation) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]          
Asset retirement obligation, beginning of period     $ 75,100 $ 34,276  
Liabilities incurred     1,468 11,557  
Liabilities settled     (719) (2,520)  
Accretion expense $ 1,037 $ 456 3,056 1,148  
Revisions in estimated cash flows     (374) 0  
Asset retirement obligation as of end of period 78,531 44,461 78,531 44,461  
Less current portion 120 195 120 195 $ 120
Asset retirement obligation, long-term $ 78,411 $ 44,266 $ 78,411 $ 44,266 $ 74,980