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Crude Oil and Natural Gas Property Information - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Oil and Gas Exploration and Production Industries Disclosures [Abstract]      
Exploration costs included in asset retirement costs $ 1.8 $ 3.3 $ 1.7
Development costs included in asset retirement costs $ 6.0 $ 1.0 $ 3.7