Annual report pursuant to Section 13 and 15(d)

Supplemental Information on Oil and Gas Producing Activities - Costs Incurred in Oil and Gas Property - Acquisition, Exploration and Development Activities (Detail)

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Supplemental Information on Oil and Gas Producing Activities - Costs Incurred in Oil and Gas Property - Acquisition, Exploration and Development Activities (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - expensed $ 23,928 $ 41,037 $ 5,708
Development 52,800    
United States
     
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - capitalized   2,602  
Exploration - expensed 11,497 38,159 2,083
Acquisition   1,630 9,495
Development 113 9,689 14,936
Total 11,610 52,080 26,514
Foreign Tax Authority
     
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - capitalized 2,942 5,916 69
Exploration - expensed 12,431 2,878 3,625
Acquisition   10,000 455
Development 54,420 4,022 8,011
Total $ 69,793 $ 22,816 $ 12,160