SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Schedule of Developed and Undeveloped Reserves (Unaudited) (Details)	12 Months Ended			12 Months Ended						12 Months Ended											12 Months Ended
	Dec. 31, 2013 bbl	Dec. 31, 2012 bbl	Dec. 31, 2011 bbl	Dec. 31, 2013 Crude Oil Equivalent (Boe) bbl	Dec. 31, 2012 Crude Oil Equivalent (Boe) bbl		Dec. 31, 2011 Crude Oil Equivalent (Boe) bbl		Dec. 31, 2010 Crude Oil Equivalent (Boe) bbl	Dec. 31, 2018 Year-over-Year Activity [Domain] Rate	Dec. 31, 2017 Year-over-Year Activity [Domain] Rate	Dec. 31, 2016 Year-over-Year Activity [Domain] Rate	Dec. 31, 2015 Year-over-Year Activity [Domain] Rate	Dec. 31, 2014 Year-over-Year Activity [Domain] Rate	Dec. 31, 2013 Year-over-Year Activity [Domain] bbl	Dec. 31, 2012 Year-over-Year Activity [Domain] bbl	Dec. 31, 2011 Year-over-Year Activity [Domain] bbl	Dec. 31, 2013 Developed [Member] bbl	Dec. 31, 2012 Developed [Member] bbl	Dec. 31, 2011 Developed [Member] bbl	Dec. 31, 2013 Undeveloped [Member] bbl	Dec. 31, 2012 Undeveloped [Member] bbl	Dec. 31, 2011 Undeveloped [Member] bbl
Schedule of Developed and Undeveloped Reserves [Line Items]
Proved Developed and Undeveloped Reserves, Net	265,774,000	192,810,000	169,248,000	265,774,000	192,810,000	[1]	169,248,000	[2]	143,436,000									75,553,000	81,753,000	78,558,000	190,221,000	111,057,000	90,690,000
Undeveloped Reserves Converted to Developed	0	0																3,212,000	7,655,000		(3,212,000)	(7,655,000)
Revisions of Previous Estimates	(46,480,000)	(58,639,000)		(46,480,000)	(58,639,000)		(25,683,000)								46,000,000	59,000,000	26,000,000	(6,751,000)	(18,318,000)		(39,729,000)	(40,321,000)
Extensions, Discoveries, and Other Additions	141,935,000	67,941,000		141,935,000	67,941,000		52,173,000								142,000,000	68,000,000	52,000,000	19,830,000	11,298,000		122,105,000	56,643,000
Purchases of Reserves	1,043,000	33,420,000		1,043,000	33,420,000		8,117,000								1,000,000	33,000,000		1,043,000	13,542,000		0	19,878,000
Dispositions	(16,104,000)	(10,891,000)		(16,104,000)	(10,891,000)		(874,000)								(16,000,000)	(11,000,000)	(800,000)	(16,104,000)	(2,713,000)		0	(8,178,000)
Production	(7,430,000)	(8,269,000)		(7,430,000)	(8,269,000)		(7,921,000)											(7,430,000)	(8,269,000)		0	0
Increase in reserves during period															73,000,000
Majority of downward revision of our previous estimate of proved reserves															(55,000,000)
Downward revisions due to adjustments in previous PUD well spacing plans															(32,000,000)
Downward revisions in reserves due to abandoned leases															(9,000,000)
Downward revisions in reserves due to our shift from vertical to horizontal drilling															(11,000,000)
Downward revisions Wattenberg Field related to PUDs that are no longer in our core drilling area															(3,000,000)
Downward revision in reserves due to increase in operating costs																(1,000,000)
Revisions due to asset performance															2,000,000	2,000,000	2,000,000
Revision in reserves due to production from uneconomic or divested wells															2,000,000
Revisions due to change in commodity pricing															1,000,000	(40,000,000)	(700,000)
Reserve discoveries from non-PUD drilling															17,000,000
Extension and discoveries from new proved undeveloped reserves															125,000,000
Extension and discoveries due to adjustments in wells spacing in Wattenberg Field and Marcellus Shale															32,000,000
Extension and discoveries in the Marcellus Shale															18,000,000
Extension and discoveries in the Utica Shale															14,000,000
Adjustments for geological reasons																(8,000,000)
PUD conversion rate										19.00%	24.00%	27.00%	22.00%	7.40%
Revision due to SEC 5 Year Rule																(13,000,000)	(29,000,000)
Revisions due to interest adjustments															3,000,000	500,000	800,000
Revisions due to transfers from PUD to PDNP																	21,000,000
Revisions due to changes in production costs																	(1,000,000)
Reserve discoveries, Eastern Operating Region																10,000,000	9,000,000
Reserve discoveries, Wattenberg Field															110,000,000	59,000,000	24,000,000
Reserve discoveries, Piceance Basin																	13,000,000
Reserve discoveries, Permian																	7,000,000
Reserves acquired, Eastern Operating Region																	1,000,000
Reserves acquired, Wattenberg Field																	5,000,000
Reserves acquired, Piceance Basin																	2,000,000
Reserves disposition, North Dakota																	(300,000)
Reserves disposition, Permian Basin																	(500,000)
Development Wells Drilled, Net Productive																0	0

[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.