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Income Taxes - Summary of Deferred Tax Assets and Liabilities (Detail) (USD $) In Thousands, unless otherwise specified | Dec. 31, 2012 | Dec. 31, 2011
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Components Of Deferred Income Tax Assets And Liabilities [Line Items] |  |
Net operating loss carryforward | $ 13,926 | $ 13,110
Bonus and stock-based compensation | 3,571 | 2,321
Derivative instruments |  | 1,888
Total deferred tax assets | 17,497 | 17,319
Oil and natural gas properties | 191,271 | 107,069
Derivative instruments | 8,455 |
Total deferred tax liabilities | 199,726 | 107,069
Total net deferred tax liability | $ 182,229 | $ 89,750

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