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Costs Incurred in Oil and Gas Property Acquisition Exploration and Development Activities (Parenthetical) (Detail) (USD $)
In Millions, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2013
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Dec. 31, 2012
|
Dec. 31, 2011
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| Costs Incurred, Oil and Gas Property Acquisition, Exploration, and Development Activities [Line Items] | |||
| Acquired CO2 | $ 20.0 | $ 16.2 | $ 15.8 |