v2.4.0.6

Disclosures About Oil and Gas Producing Activities - Additional Information (Detail)	12 Months Ended				12 Months Ended			12 Months Ended
	Dec. 31, 2012 MMBoe MBoe	Dec. 31, 2011 MMBoe MBoe	Dec. 31, 2010 MMBoe MBoe	Dec. 31, 2009 MBoe	Dec. 31, 2012 Southeast Project Pangea [Member] MMBoe	Dec. 31, 2010 Southeast Project Pangea [Member] MMBoe	Dec. 31, 2011 Working Interest Acquisition [Member] MMBoe	Dec. 31, 2011 Permian Basin [Member] MMBoe	Dec. 31, 2011 East Texas Basin [Member] MMBoe	Dec. 31, 2010 North Bald Prairie [Member] MMBoe Bcf	Dec. 31, 2012 Project Pangea [Member] MMBoe	Dec. 31, 2010 Project Pangea [Member] MMBoe	Dec. 31, 2010 Natural Gas (MMcf) [Member]	Dec. 31, 2009 Natural Gas (MMcf) [Member]	Dec. 31, 2010 NGLs (MBbls) [Member]	Dec. 31, 2009 NGLs (MBbls) [Member]	Dec. 31, 2010 Oil (MBbls) [Member]	Dec. 31, 2009 Oil (MBbls) [Member]	Dec. 31, 2012 Natural Gas [Member] MMBoe	Dec. 31, 2012 Technical Evaluations [Member] MMBoe
Reserve Quantities [Line Items]
Production	2.9	2.4
Percentage of production attributable to assets	99.40%	99.00%
Extensions and discoveries	38.9	25.5
Downward revisions	17.5	7.5	0.2							0.1	3.3								2.4	2.9
Economic revisions					8.9			5.6	2.2
Extensions and discoveries attributable to Wolffork oil shale resource play		24.2
MMBoe of proved reserves	95,479	76,975	50,715	36,488			10.5
Percentage of working interest acquisition							38.00%
Positive revisions		0.3	10.1
Positive revisions attributable to planned processing upgrades						9.2
Positive revisions attributable to increase in commodity price			1.1
Commodity Prices													4.38	3.87	39.25	27.20	79.40	56.04
Proved reserves removed			0.2							0.9
Proved reserves removed due to performance revisions												0.1

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Downward performance revisions to our proved reserves.

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields.

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Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in the Wolffork.

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Percentage of production attributable to assets in the Permian Basin.

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Production measured in million barrels of oil equivalent.

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The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable.

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Proved Reserves Removed

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Upward performance revisions to our proved reserves.

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Upward Revisions Attributable To Price

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The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

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Percentage of voting equity interests acquired in the business combination.

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