Contingencies (Details 2) (Pending Litigation [Member], USD $) In Millions, unless otherwise specified	1 Months Ended	12 Months Ended
Feb. 28, 2011	Dec. 31, 2012 A
Pending Litigation [Member]
Litigations
Percentage of overriding royalty interest in production (as a percent)		7.46875%
Acres of land for which an overriding royalty interest is claimed (in acres)		22,000
Damages sought value (in dollars)	$ 5.1

The value (monetary amount) of the award the plaintiff seeks in the legal matter.

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

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-Publisher FASB

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Statement of Financial Accounting Standard (FAS)

-Number 5

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

+ Details