Annual report pursuant to Section 13 and 15(d)

Supplemental Information On Oil And Gas Exploration And Production Activities (Oil and Gas Reserves) (Details)

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Supplemental Information On Oil And Gas Exploration And Production Activities (Oil and Gas Reserves) (Details)
 12 Months Ended
Dec. 31, 2013
MBbls
Dec. 31, 2012
MBbls
Dec. 31, 2011
MBbls
Oil [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 8,106 13,954 16,597
Purchases in oil and gas reserves in place 0 0 2
Extensions and discoveries 2,765 4,732 3,723
Sales of oil and gas reserves in place 0 (7,875) 0
Revisions of prior reserve estimates (208) (382) (4,240)
Current production (2,317) (2,323) (2,128)
End of period 8,346 8,106 13,954
Proved developed reserves 5,609 5,175 6,780
Proved undeveloped reserves 2,737 2,931 7,174
Gas [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 33,771 15,728 16,158
Purchases in oil and gas reserves in place 0 0 19
Extensions and discoveries 123,597 31,265 2,091
Sales of oil and gas reserves in place 0 (11,757) 0
Revisions of prior reserve estimates (2,031) (357) (1,662)
Current production (8,891) (1,108) (878)
End of period 146,446 33,771 15,728
Proved developed reserves 94,552 18,482 6,152
Proved undeveloped reserves 51,894 15,289 9,576
Natural Gas Liquids [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 145 2,791 3,107
Purchases in oil and gas reserves in place 0   0
Extensions and discoveries 5,850 148 217
Sales of oil and gas reserves in place 0 (2,729) 0
Revisions of prior reserve estimates 0   (474)
Current production (320) (65) (59)
End of period 5,675 145 2,791
Proved developed reserves 3,527 44 705
Proved undeveloped reserves 2,148 101 2,086
Diamondback Energy, Inc [Member] | Oil [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 5,606 3,874  
Change in ownership interest in Diamondback (3,720) 0  
Purchases in oil and gas reserves in place 528 1,543  
Extensions and discoveries 1,227 665  
Revisions of prior reserve estimates (428) (314)  
Current production (146) (162)  
End of period 3,067 5,606  
Proved developed reserves 1,425 1,539  
Proved undeveloped reserves 1,642 4,068  
Diamondback Energy, Inc [Member] | Gas [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 7,398 4,398  
Change in ownership interest in Diamondback (4,909) 0  
Purchases in oil and gas reserves in place 752 2,292  
Extensions and discoveries 1,741 804  
Revisions of prior reserve estimates (417) 82  
Current production (124) (178)  
End of period 4,441 7,398  
Proved developed reserves 2,263 2,753  
Proved undeveloped reserves 2,178 4,645  
Diamondback Energy, Inc [Member] | Natural Gas Liquids [Member]
      
Proved Developed and Undeveloped Reserves [Roll Forward]      
Beginning of the period 1,766 1,080  
Change in ownership interest in Diamondback (1,171) 0  
Purchases in oil and gas reserves in place 120 540  
Extensions and discoveries 331 186  
Revisions of prior reserve estimates (249) (1)  
Current production (26) (39)  
End of period 771 1,766  
Proved developed reserves 358 641  
Proved undeveloped reserves 413 1,124