Supplemental Information on Oil & Natural Gas Exploration and Production Activities (unaudited) - Additional Information (Detail)	12 Months Ended
Dec. 31, 2015 $ / Bbls $ / Mcf	Dec. 31, 2014 $ / Bbls $ / Mcf
Oil
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Average prices used in calculations \| $ / Bbls	50.28	94.99
Natural Gas
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Average prices used in calculations \| $ / Mcf	2.59	4.35

The revenues derived from sales of oil or gas in each geographic area during the reporting period divided by the number of barrels of oil produced or thousands of cubic feet of gas produced.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1204
-Paragraph (b)
-Subparagraph (1)

Name:	us-gaap_AverageSalesPrices
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration