Annual report pursuant to Section 13 and 15(d)

Supplemental Information On Oil And Gas Exploration And Production Activities (Costs Incurred In Oil And Gas Property Acquisition And Development Activities) (Details)

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Supplemental Information On Oil And Gas Exploration And Production Activities (Costs Incurred In Oil And Gas Property Acquisition And Development Activities) (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Oil and Gas Exploration and Production Industries Disclosures [Abstract]      
Acquisition $ 513,904 $ 119,522 $ 17,627
Development of proved undeveloped properties 121,787 123,489 64,652
Exploratory 93,397 3,994 0
Recompletions 24,643 17,259 16,917
Capitalized asset retirement obligation 2,195 1,390 1,328
Total $ 755,926 $ 265,654 $ 100,524