Acquired Proved Reserves by Type of Reserve, Percentage

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- Definition

Acquisition Oil and Gas Properties, Number of Wells

+ References

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- Definition

Discount Rate Assumed To Measure Future Net Cash Flow of Proved Oil and Gas Reserves

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- Definition

The amount of Accounts Payable recognized as of the acquisition date.

+ References

No definition available.

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- Definition

The amount of Accounts Receivable recognized as of the acquisition date.

+ References

No definition available.

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- Definition

The amount of Asset Retirement Obligation recognized as of the acquisition date.

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No definition available.

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- Definition

The Net amount recognized as of the acquisition date for the aggregate identifiable assets acquired in excess of or less than the aggregate liabilities assumed.

+ References

No definition available.

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- Definition

The amount of Proved Properties recognized as of the acquisition date.

+ References

No definition available.

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- Definition

The amount of Unproved Properties assumed at the acquisition date.

+ References

No definition available.

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- Definition

Percentage of Undeveloped Portion of Proved Reserves

+ References

No definition available.

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- Definition

Proved Developed And Undeveloped Reserves, Net, Energy

+ References

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- Definition

Significant Acquisitions and Disposals, Percentage of Undivided Interest, Sale

+ References

No definition available.

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- Definition

The adjustment to expense previously capitalized costs of drilling exploratory wells when proved reserves are not found or when the entity obtains information that raises substantial doubt about the economic or operational viability of the project.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 360

-Section 40

-Paragraph 1

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 27, 28, 40, 41

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Fractional interest owned based on working interests or other economic arrangements of lease area on which wells have not been drilled or completed to a point that would permit the production of commercial quantities of oil and gas regardless of whether or not such area contains proved reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 5

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- Definition

The expense recorded to reduce the value of oil and gas assets consisting of proved properties and unproved properties as the estimate of future successful production from these properties is reduced.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 19

-Paragraph 27, 28, 29

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

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The net result for the period of deducting operating expenses from operating revenues.

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- Definition

The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 16

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Glossary Investing Activities

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Total revenue from sale of goods and services rendered during the reporting period, in the normal course of business, reduced by sales returns and allowances, and sales discounts.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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-SubTopic 10

-Section S99

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-Subparagraph (SX 210.5-03.1)

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-Name Regulation S-X (SX)

-Number 210

-Section 03

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-Article 5

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The value of all consideration given or received by the Entity in the significant acquisition or disposal.

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Acquisition and Dispositions of Oil and Gas Properties (Details) (USD $)	3 Months Ended								12 Months Ended				12 Months Ended		0 Months Ended		12 Months Ended	0 Months Ended					0 Months Ended										0 Months Ended					0 Months Ended	12 Months Ended	0 Months Ended
	Dec. 31, 2012 MMBoe	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011 MMBoe	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 MMBoe	Dec. 31, 2011 MMBoe	Dec. 31, 2010 MMBoe	Dec. 31, 2009 MMBoe	Dec. 31, 2011 Alabama Shale	Dec. 31, 2011 Alabama Shale Well	Feb. 21, 2012 Feb 21, 2012, Reeves County well acre	Feb. 14, 2012 Feb 14, 2012, Permian Basin MMBoe	Dec. 31, 2012 Feb 14, 2012, Permian Basin	Feb. 14, 2012 Feb 14, 2012, Permian Basin Oil Reserves	Feb. 14, 2012 Feb 14, 2012, Permian Basin Natural Gas Liquids Reserves	Feb. 14, 2012 Feb 14, 2012, Permian Basin Natural Gas Reserves	Dec. 31, 2012 December 2012, Permian Basin	Dec. 31, 2012 Unproved Leasehold Properties	Dec. 27, 2011 Dec 27, 2011, Permian Basin MMBoe	Dec. 27, 2011 Dec 27, 2011, Permian Basin Oil Reserves	Dec. 27, 2011 Dec 27, 2011, Permian Basin Natural Gas Liquids Reserves	Dec. 27, 2011 Dec 27, 2011, Permian Basin Natural Gas Reserves	Nov. 16, 2011 Nov 16, 2011, Permian Basin MMBoe	Nov. 16, 2011 Nov 16, 2011, Permian Basin Oil Reserves	Nov. 16, 2011 Nov 16, 2011, Permian Basin Natural Gas Liquids Reserves	Nov. 16, 2011 Nov 16, 2011, Permian Basin Natural Gas Reserves	Dec. 31, 2012 July 2011, Permian Basin	Dec. 31, 2012 April 2011, Permian Basin acre	Dec. 15, 2010 Dec 15, 2010, Permian Basin MMBoe	Dec. 15, 2010 Dec 15, 2010, Permian Basin Oil Reserves	Dec. 15, 2010 Dec 15, 2010, Permian Basin Natural Gas Liquids Reserves	Dec. 15, 2010 Dec 15, 2010, Permian Basin Natural Gas Reserves	Dec. 09, 2010 Dec 9, 2010, Permian Basin MMBoe	Sep. 30, 2010 Sep 30, 2010, Permian Basin MMBoe	Dec. 31, 2011 Sep 30, 2010, Permian Basin	Sep. 30, 2010 Sep 30, 2010, Permian Basin Oil Reserves	Sep. 30, 2010 Sep 30, 2010, Permian Basin Natural Gas Liquids Reserves	Sep. 30, 2010 Sep 30, 2010, Permian Basin Natural Gas Reserves	May 01, 2012 Contingent Sales Agreement Feb 21, 2012, Reeves County acre
Significant Acquisitions and Disposals [Line Items]
Impairment of oil and gas properties									$ 21,545,000
Discount rate assumed for valuation (in percent)									10.00%
Significant Acquisitions and Disposals, Percentage of Undivided Interest, Sale															50.00%																												50.00%
Acquisition Oil and Gas Properties, Number of Wells															3
Cash received from sale of oil properties															18,000,000
Net acres															4,829																	11,000											51,720
Consideration - Purchase Price																67,615,000					18,723,000	18,000,000	60,017,000				161,967,000				20,000,000	37,000,000	73,630,000				103,000,000	188,314,000
Proved reserves acquired	346.4				343.1				346.4	343.1	302.9	257.8				8.2							3.4				13.6						7.6				0	18
Percentage of undeveloped portion of proved reserves									59.00%	69.00%	77.00%					81.00%							77.00%				76.00%						92.00%					89.00%
Acquired proved reserves by type of reserve, percentage																		64.00%	22.00%	14.00%				61.00%	24.00%	15.00%		59.00%	25.00%	16.00%				62.00%	24.00%	14.00%				65.00%	22.00%	13.00%
Exploration Abandonment and Impairment Expense													39,700,000	15,500,000
Recognized amounts of identifiable assets acquired and liabilities assumed
Proved properties																65,581,000							36,068,000				151,544,000						41,066,000					151,747,000
Unproved leasehold properties																911,000							23,686,000				7,883,000						32,500,000					35,360,000
Accounts receivable																1,358,000							680,000				3,070,000						143,000					1,461,000
Accounts payable																(25,000)							(244,000)				(388,000)											(112,000)
Asset retirement obligation																(210,000)							(173,000)				(142,000)						(79,000)					(142,000)
Total identifiable net assets																67,615,000							60,017,000				161,967,000						73,630,000					188,314,000
Revenue, Net	433,046,000	295,324,000	470,355,000	418,444,000	288,148,000	378,568,000	330,399,000	486,364,000	1,617,169,000	1,483,479,000	1,578,534,000						11,700,000																						5,000,000
Operating Income (Loss)	$ 115,166,000	$ 19,458,000	$ 220,598,000	$ 104,170,000	$ 31,641,000	$ 150,412,000	$ 106,335,000	$ 159,881,000	$ 459,392,000	$ 448,269,000	$ 493,377,000						$ 3,100,000																						$ 2,100,000