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Property, Plant and Equipment - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Property, Plant and Equipment [Line Items]        
Impairment of oil and gas properties $ 208 $ 2,203 $ 706 $ 2,571
Unproved property leases [Member]
       
Property, Plant and Equipment [Line Items]        
Impairment of oil and gas properties $ 208 $ 2,203 $ 706 $ 2,571