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Organization and Basis of Preparation (Details)	Dec. 31, 2013 item
Organization and Basis of Preparation
Number of wholly owned subsidiaries	3

X

- Definition

Represents the number of wholly owned subsidiaries of the entity.

+ References

No definition available.

+ Details

Name:	epm_NumberOfWhollyOwnedSubsidiaries
Namespace Prefix:	epm_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration