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Revenue (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Disclosure Of Revenue [Line Items]      
Sale of crude oil $ 545,490 $ 279,162 $ 145,193
Sale of gas 55,671 50,960 47,477
Revenue $ 601,161 $ 330,122 $ 192,670