Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Producing Activities - Net Proved Reserves (Detail)

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Supplemental Information on Oil and Gas Producing Activities - Net Proved Reserves (Detail)
12 Months Ended
Dec. 31, 2013
MBbls
Dec. 31, 2012
MBbls
Dec. 31, 2011
MBbls
Dec. 31, 2010
MBbls
Oil
       
Proved Reserves:        
Beginning Balance 7,488 6,048 6,922  
Production (1,549) (1,741) (1,868)  
Revisions of previous estimates 771 2,200 959  
Extensions and discoveries 522 981 35  
Ending Balance 7,232 7,488 6,048  
Proved Developed Reserves 3,305 3,750 3,854 5,029
Gas
       
Proved Reserves:        
Beginning Balance 1,544,000 1,925,000 23,000  
Production (325,000) (532,000) (255,000)  
Revisions of previous estimates 114,000 151,000 31,000  
Extensions and discoveries     2,126,000  
Ending Balance 1,333,000 1,544,000 1,925,000  
Proved Developed Reserves 1,333,000 1,544,000 856,000 23,000