Annual report pursuant to Section 13 and 15(d)

Oil And Natural Gas Properties And Equipment (Schedule Of Capitalized Exploratory Well Costs) (Detail)

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Oil And Natural Gas Properties And Equipment (Schedule Of Capitalized Exploratory Well Costs) (Detail)
Dec. 31, 2015
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Dec. 31, 2014
USD ($)
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Dec. 31, 2013
USD ($)
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Supplemental Information On Oil And Gas Producing Activities [Abstract]      
Exploratory well costs capitalized for greater than one year   $ 8,900,000 $ 16,700,000
Total capitalized exploratory well costs   $ 8,900,000 $ 16,700,000
Number of projects capitalized for greater than a year | item 0 1 2