BUSINESS SEGMENTS Business segments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Segment revenues	$ 141,067	$ 77,116	$ 121,305	$ 71,826	$ 97,139	$ 32,720	$ 99,740	$ 91,006	$ 411,314	$ 320,605	$ 337,289
Segment income (loss) before income taxes	21,258	(25,373)	26,293	(63,447)	(31,392)	(43,279)	29,391	10,884	(41,269)	(34,396)	34,364
Expenditures for segment long-lived assets									404,606	659,952	480,390
Segment assets	2,025,203				1,826,848				2,025,203	1,826,848
Oil and Gas Properties
Segment Reporting Information [Line Items]
Segment revenues									341,527	275,234	273,819
Segment income (loss) before income taxes									79,527	103,111	138,616
Expenditures for segment long-lived assets									403,227	656,443	479,027
Segment assets	1,934,466				1,723,011				1,934,466	1,723,011
Marketing
Segment Reporting Information [Line Items]
Segment revenues									69,787	45,371	63,470
Segment income (loss) before income taxes									(298)	349	639
Segment assets	20,342				11,090				20,342	11,090
Corporate and Other
Segment Reporting Information [Line Items]
Segment income (loss) before income taxes									(120,498)	(137,856)	(104,891)
Expenditures for segment long-lived assets									1,379	3,509	1,363
Segment assets	67,610				92,747				67,610	92,747
Assets Held-for-sale
Segment Reporting Information [Line Items]
Segment assets	$ 2,785				$ 0				$ 2,785	$ 0