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

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- Definition Represents the number of wholly owned subsidiaries of the entity. + References No definition available. + Details
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Namespace Prefix: | epm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration