SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Changes in Estimated Proved Reserves (Unaudited) (Details)	12 Months Ended
	Dec. 31, 2013 bbl		Dec. 31, 2012 bbl		Dec. 31, 2011 bbl		Dec. 31, 2010 bbl
Reserve Quantities [Line Items]
Proved Reserves	265,774,000		192,810,000		169,248,000
Undeveloped Reserves Converted to Developed	0		0
Revisions of Previous Estimates	(46,480,000)		(58,639,000)
Extensions, Discoveries, and Other Additions	141,935,000		67,941,000
Purchases of Reserves	1,043,000		33,420,000
Dispositions	(16,104,000)		(10,891,000)
Production	(7,430,000)		(8,269,000)
Crude Oil (Bbls)
Reserve Quantities [Line Items]
Proved Reserves	93,830,000		59,310,000	[1]	37,636,000	[2]	23,236,000
Revisions of Previous Estimates	(18,420,000)		(6,729,000)		(1,904,000)
Extensions, Discoveries, and Other Additions	55,759,000		27,482,000		17,092,000
Purchases of Reserves	343,000		10,801,000		1,605,000
Dispositions	(252,000)		(7,854,000)		(435,000)
Production	(2,910,000)		(2,026,000)		(1,958,000)
Proved Developed Reserves	23,997,000		20,412,000	[1]	16,910,000	[2]	8,287,000
Proved Undeveloped Reserve	69,833,000		38,898,000	[1]	20,726,000	[2]	14,949,000
Natural Gas (Mcf)
Reserve Quantities [Line Items]
Proved Reserves	739,640,000		604,038,000	[1]	672,145,000	[2]	657,306,000
Revisions of Previous Estimates	(117,068,000)		(289,436,000)		(161,654,000)
Extensions, Discoveries, and Other Additions	365,563,000		172,933,000		176,689,000
Purchases of Reserves	2,894,000		87,212,000		32,761,000
Dispositions	(94,927,000)		(6,406,000)		(2,070,000)
Production	(20,860,000)		(32,410,000)		(30,887,000)
Proved Developed Reserves	220,387,000		281,925,000	[1]	299,369,000	[2]	227,341,000
Proved Undeveloped Reserve	519,253,000		322,113,000	[1]	372,776,000	[2]	429,965,000
Natural Gas Liquids (Bbls)
Reserve Quantities [Line Items]
Proved Reserves	48,671,000		32,827,000	[1]	19,588,000	[2]	10,649,000
Revisions of Previous Estimates	(8,549,000)		(3,671,000)		3,163,000
Extensions, Discoveries, and Other Additions	25,249,000		11,637,000		5,633,000
Purchases of Reserves	217,000		8,084,000		1,052,000
Dispositions	(30,000)		(1,970,000)		(94,000)
Production	(1,043,000)		(841,000)		(815,000)
Proved Developed Reserves	14,825,000		14,353,000	[1]	11,753,000	[2]	4,013,000
Proved Undeveloped Reserve	33,846,000		18,474,000	[1]	7,835,000	[2]	6,636,000
Crude Oil Equivalent (Boe)
Reserve Quantities [Line Items]
Proved Reserves	265,774,000		192,810,000	[1]	169,248,000	[2]	143,436,000
Revisions of Previous Estimates	(46,480,000)		(58,639,000)		(25,683,000)
Extensions, Discoveries, and Other Additions	141,935,000		67,941,000		52,173,000
Purchases of Reserves	1,043,000		33,420,000		8,117,000
Dispositions	(16,104,000)		(10,891,000)		(874,000)
Production	(7,430,000)		(8,269,000)		(7,921,000)
Proved Developed Reserves	75,553,000		81,753,000	[1]	78,558,000	[2]	50,190,000
Proved Undeveloped Reserve	190,221,000		111,058,000	[1]	90,690,000	[2]	93,246,000
Permian Asset Group | Crude Oil (Bbls)
Reserve Quantities [Line Items]
Proved Reserves					7,825,000	[2]
Proved Developed Reserves					1,815,000	[2]
Proved Undeveloped Reserve					6,010,000	[2]
Permian Asset Group | Natural Gas (Mcf)
Reserve Quantities [Line Items]
Proved Reserves					6,242,000	[2]
Proved Developed Reserves					1,750,000	[2]
Proved Undeveloped Reserve					4,492,000	[2]
Permian Asset Group | Natural Gas Liquids (Bbls)
Reserve Quantities [Line Items]
Proved Reserves					1,970,000	[2]
Proved Developed Reserves					550,000	[2]
Proved Undeveloped Reserve					1,420,000	[2]
Permian Asset Group | Crude Oil Equivalent (Boe)
Reserve Quantities [Line Items]
Proved Reserves					10,835,000	[2]
Proved Developed Reserves					2,657,000	[2]
Proved Undeveloped Reserve					8,179,000	[2]
Piceance and NECO Asset Group [Member] | Crude Oil (Bbls)
Reserve Quantities [Line Items]
Proved Developed Reserves	148,000	[2]
Piceance and NECO Asset Group [Member] | Natural Gas (Mcf)
Reserve Quantities [Line Items]
Proved Developed Reserves	83,656,000	[2]
Piceance and NECO Asset Group [Member] | Crude Oil Equivalent (Boe)
Reserve Quantities [Line Items]
Proved Developed Reserves	14,091,000	[2]

[1] Includes estimated reserve data related to our Piceance and NECO assets, which were divested in June 2013. See Note 14, Assets Held for Sale, Divestitures and Discontinued Operations, for additional details related to the divestiture of our Piceance and NECO assets. Total proved reserves include 148 MBbls of crude oil and 83,656 MMcf of natural gas, for an aggregate of 14,091 MBoe of crude oil equivalent related to our Piceance and NECO assets. There were no proved undeveloped reserves attributable to the Piceance and NECO assets as of December 31, 2012.

[2] Includes estimated reserve data related to our Permian Basin assets, which were divested in February 2012. See Note 14, Assets Held for Sale, Divestitures and Discontinued Operations, for additional details related to the divestiture of our Permian Basin assets. Total proved reserves included 7,825 MBbls of crude oil, 6,242 MMcf of natural gas and 1,970 MBbls of NGLs, for an aggregate of 10,835 Mboe of crude oil equivalent, related to our Permian asset group. Total proved developed reserves related to those assets included 1,815 MBbls, 1,750 MMcf, 550 MBbls and 2,657 MBoe, respectively, and proved undeveloped reserves included 6,010 MBbls, 4,492 MMcf, 1,420 MBbls and 8,179 MBoe, respectively.