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Fair Value Measurements - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended
Sep. 30, 2013
Jun. 30, 2013
Dec. 31, 2012
Sep. 30, 2012
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Interest and dividends         $ 1,200,000 $ 1,400,000 $ 1,400,000
Mark-to-market gain (loss)         3,900,000 4,700,000 2,300,000
Impairment 7,012,000 741,000 34,273,000 1,281,000 7,753,000 35,554,000 38,681,000
Gulf Coast
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on oil and gas properties         7,000,000   7,500,000
Mississippi
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on oil and gas properties           31,100,000  
North Texas
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on oil and gas properties           3,200,000  
East Texas
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment on oil and gas properties             31,200,000
Surface Property | Fair Value, Measurements, Nonrecurring
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment         741,000 1,281,000  
Natural gas | Fair Value, Inputs, Level 3
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Number of natural gas basis swap         4    
Natural gas | Fair Value, Measurements, Nonrecurring
              
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]              
Impairment         $ 7,012,000 $ 34,273,000 $ 38,681,000