BUSINESS SEGMENTS Business segments (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total revenues	$ 168,634	$ 231,100	$ 50,960	$ 144,632	$ 407,691	$ 224,556	$ 101,303	$ 122,657	$ 595,326	$ 856,207	$ 392,665
Segment income (loss) before income taxes	5,274	$ (62,661)	$ (76,986)	$ 27,785	138,085	$ 89,473	$ (48,028)	$ (2,302)	(106,588)	177,228	(32,963)
Expenditures for segment long-lived assets									604,668	628,592	404,606
Segment assets	2,370,543				2,331,140				2,370,543	2,331,140
Oil and Gas Properties
Segment Reporting Information [Line Items]
Total revenues									584,406	784,636	322,878
Segment income (loss) before income taxes									31,429	344,149	81,913
Expenditures for segment long-lived assets									599,617	623,912	403,227
Segment assets	2,294,288				2,258,060				2,294,288	2,258,060
Marketing
Segment Reporting Information [Line Items]
Total revenues									10,920	71,571	69,787
Segment income (loss) before income taxes									(797)	(445)	(297)
Segment assets	4,217				6,979				4,217	6,979
Corporate and Other
Segment Reporting Information [Line Items]
Segment income (loss) before income taxes									(137,220)	(166,476)	(114,579)
Expenditures for segment long-lived assets									5,051	4,680	$ 1,379
Segment assets	69,164				63,227				69,164	63,227
Assets Held-for-sale
Segment Reporting Information [Line Items]
Segment assets	$ 2,874				$ 2,874				$ 2,874	$ 2,874