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Property, Plant and Equipment - Schedule of Asset Retirement Obligations (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Oil And Gas Property [Abstract]      
Asset retirement obligations $ 214,733 $ 220,049  
Fair value of asset retirement obligations acquired 244,766 699  
Obligations settled (112,946) (32,573)  
Accretion expense 35,344 19,295 $ 21,829
Obligations incurred 358 4,213  
Changes in estimate 562 3,050  
Asset retirement obligations 382,817 214,733 $ 220,049
Less: Current portion (68,965) (39,741)  
Long-term portion $ 313,852 $ 174,992