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OIL AND NATURAL GAS OPERATIONS (Unaudited) - Costs Incurred (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Property acquisition:      
Proved $ 4,066 $ 1,866 $ 2,582
Unproved 143,667 85,690 68,514
Exploration 349,463 649,764 972,164
Development 89,624 372,177 408,949
Total costs incurred $ 586,820 $ 1,109,497 $ 1,452,209