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Oil and Gas Producing Activities - Schedule of Information Regarding Costs Incurred for Oil and Gas Property Acquisition, Development and Exploration Activities (Parenthetical) (Detail) (USD $)
In Thousands, unless otherwise specified |
12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Development costs | $ 285,039 | $ 182,522 | $ 56,915 |
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Non-cash asset retirement obligations [Member]
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| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Development costs | $ 409 | $ 1,200 | $ 604 |