DERIVATIVES - COMPONENTS OF DERIVATIVE GAINS (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Components of the derivative gain (loss)
Derivative gain	$ 2,206	$ 37,894	$ (11,724)	$ 51,272
Commodity Derivative
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	4,348	37,717	15,749	88,372
Change in fair value gain (loss)	(2,142)	177	(27,473)	(37,100)
Derivative gain	2,206	37,894	(11,724)	51,272
Commodity Derivative | Oil
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	4,348	37,027	15,749	86,325
Commodity Derivative | Natural gas
Components of the derivative gain (loss)
Derivative cash settlement gain (loss)	$ 0	$ 690	$ 0	$ 2,047