Major Customers - Additional Information (Detail)	12 Months Ended
Dec. 31, 2013 Customer	Dec. 31, 2012 Customer	Dec. 31, 2011 Customer
Concentration Risk [Line Items]
Number of customers accounted more than 10% of total oil and gas revenues	4	2	2
Minimum percentage of oil and gas sales revenue for identifying major customer	10.00%	10.00%	10.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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