v2.4.0.6
Disclosures About Oil and Gas Producing Activities - Commodity Prices Inclusive of Adjustments for Quality and Location Used in Determining Future Net Revenues Related to Standardized Measure Calculation (Detail)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Oil (MBbls) [Member]
     
Average Sales Price and Production Costs Per Unit of Production [Line Items]      
Commodity Prices 90.21 89.65 74.90
NGLs (MBbls) [Member]
     
Average Sales Price and Production Costs Per Unit of Production [Line Items]      
Commodity Prices 37.88 49.63 39.25
Natural Gas (MMcf) [Member]
     
Average Sales Price and Production Costs Per Unit of Production [Line Items]      
Commodity Prices 2.62 3.97 4.13