OIL AND NATURAL GAS PROPERTIES (Details) (USD $)	3 Months Ended	9 Months Ended	12 Months Ended			3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Unevaluated Oil and Gas Leaseholds	Sep. 30, 2012 Unevaluated Oil and Gas Leaseholds	Sep. 30, 2013 Unevaluated Oil and Gas Leaseholds	Sep. 30, 2012 Unevaluated Oil and Gas Leaseholds
Oil and Natural Gas Properties
Amount of unevaluated property costs transferred to the full cost pool	$ 655,700,000
Unevaluated	1,982,188,000	1,982,188,000	1,982,188,000		2,326,598,000
Interest costs capitalized						52,600,000	19,400,000	157,600,000	22,800,000
Ceiling Limitation Disclosures
First day average of the West Texas Intermediate (WTI) spot price (in dollars per barrel)			95.20	94.97
First day average of the Henry Hub price (in dollars per Mmbtu)			3.61	2.83
Full cost ceiling impairment	909,098,000	909,098,000
Full cost ceiling impairment, after tax		$ 574,800,000