Annual report pursuant to Section 13 and 15(d)

Estimated Quantities of Net Proved, Proved Developed and Proved Undeveloped Oil, Ngls and Natural Gas Reserves (Parenthetical) (Detail)

v2.4.0.6
Estimated Quantities of Net Proved, Proved Developed and Proved Undeveloped Oil, Ngls and Natural Gas Reserves (Parenthetical) (Detail)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Reserve Quantities [Line Items]      
Revision of price (in Bcfe) 8.0 6.3 17.5
Revisions due to NGL marketing arrangement (in Bcfe)   16.5  
Discoveries
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe     21.9
Extensions
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe     7.2
Tahoe field (Viosca Knoll 784)
      
Reserve Quantities [Line Items]      
Revisions related to compressor project (in Bcfe)   11.3  
Fairway Properties
      
Reserve Quantities [Line Items]      
Revision of reserve   10.6  
Main Pass 98 | Discoveries
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe   13.9  
Ship Shoal 349/359 | Discoveries
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe   8.0  
Main Pass 108 | Discoveries
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe   3.7  
Yellow Rose Properties
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe 69.5    
Yellow Rose Properties | Revisions From Negative Performance
      
Reserve Quantities [Line Items]      
Revision of reserve 17.9    
High Island 22
      
Reserve Quantities [Line Items]      
Changes due to extensions and discoveries, Bcfe 16.2