DERIVATIVES - COMPONENTS OF DERIVATIVE GAINS (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Components of the derivative gain (loss)
Derivative gain	$ (12,923)	$ (5,478)	$ (13,930)	$ 13,378
Commodity Derivative
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	3,893	15,189	11,401	50,655
Change in fair value gain (loss)	(16,816)	(20,667)	(25,331)	(37,277)
Derivative gain	(12,923)	(5,478)	(13,930)	13,378
Commodity Derivative | Oil
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	3,893	14,507	11,401	49,298
Commodity Derivative | Natural gas
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	$ 0	$ 682	$ 0	$ 1,357