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Supplemental Information on Oil and Natural Gas Producing Activities - Capitalized Costs Related to Oil, Natural Gas and NGL Producing Activities (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Oil and natural gas properties      
Proved $ 10,972,816 [1] $ 12,262,921 [1] $ 8,969,296
Unproved 531,606 865,863 689,393
Total oil and natural gas properties 11,504,422 13,128,784 9,658,689
Less: accumulated depreciation, depletion and impairment (5,762,969) (5,231,182) (4,791,534)
Net oil and natural gas properties capitalized costs $ 5,741,453 $ 7,897,602 $ 4,867,155
[1] Includes cumulative capitalized interest of approximately $23.4 million and $11.7 million at December 31, 2013 and 2012, respectively.