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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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

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- Definition The notional volumes in commodity derivative contracts as a percentage of current production. + References No definition available. + Details
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- Definition Gain (loss) recognized on the sale of oil and gas property or timber property. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 28 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585 + Details
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- Definition The cash inflow to dispose of long-lived, physical assets and mineral interests in oil and gas properties used for normal oil and gas operations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 16 -Subparagraph c -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3179-108585 + Details
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