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
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - expensed $ 46,453 $ 15,358 $ 23,928
International [Member]      
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - capitalized     2,942
Exploration - expensed 28,052 15,358 12,431
Development 60,397 79,722 54,420
Total $ 88,449 95,080 69,793
United States [Member]      
Costs Incurred in Oil and Gas Property Acquisition, Exploration and Development Activities      
Exploration - expensed     11,497
Development   8 113
Total   $ 8 $ 11,610