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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2012
13 to 24 months [Member]
Dec. 31, 2012
25 to 36 months [Member]
Dec. 31, 2012
37 to 60 months [Member]
Nov. 30, 2011
Barnett shale [Member]
Dec. 31, 2012
Proved oil and gas properties [Member]
Dec. 31, 2011
Proved oil and gas properties [Member]
Dec. 31, 2010
Proved oil and gas properties [Member]
Dec. 31, 2012
Unproved property leases [Member]
Dec. 31, 2011
Unproved property leases [Member]
Dec. 31, 2010
Unproved property leases [Member]
Dec. 31, 2012
Furniture and equipment [Member]
Minimum [Member]
Dec. 31, 2012
Furniture and equipment [Member]
Maximum [Member]
Dec. 31, 2012
Buildings [Member]
Interest Cost Capitalized And Depreciation And Amortization Expenses For Property, Plant and Equipment [Line Items]                                
Proceeds from sale of property   $ 2,202,000         $ 2,202,000                  
Gain (loss) on sale of properties   (207,000)         (207,000)                  
US Results of Operations, Impairment of Oil and Gas Properties 3,581,000 3,610,000 11,967,000         0 0 0 3,600,000 3,600,000 12,000,000      
Capitalized interest costs 3,300,000 3,100,000 0                          
Estimated life of assets                           3 years 7 years 20 years
Past-due receivables from counterparties 0                              
Contractual commodity derivative volume, percent 110.00%     100.00% 75.00% 50.00%                    
Restricted stock awards vesting period 3 years                              
Excess tax deduction related to stock-based compensation $ 2,700,000