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Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) (Oil and Gas Reserves) (Details) | 12 Months Ended
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Dec. 31, 2015 MMcf MBbls | Dec. 31, 2015 MMcf MBbls | Dec. 31, 2014 MMcf MBbls | Dec. 31, 2014 MMcf MBbls | Dec. 31, 2013 MMcf MBbls | Dec. 31, 2013 MMcf MBbls
Oil and condensate sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  | 9,497 |  | 8,346 |  | 8,106
Purchases in oil and gas reserves in place |  | 0 |  | 173 |  | 0
Extensions and discoveries |  | 2,413 |  | 4,975 |  | 2,765
Revisions of prior reserve estimates |  | (2,553) |  | (1,313) |  | (208)
Current production |  | (2,899) |  | (2,684) |  | (2,317)
End of period |  | 6,458 |  | 9,497 |  | 8,346
Proved developed reserves | 6,120 | 6,120 | 5,719 | 5,719 | 5,609 | 5,609
Proved undeveloped reserves | 338 | 338 | 3,778 | 3,778 | 2,737 | 2,737
Natural gas liquids sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period | 719,006 | 719,006 | 146,446 | 146,446 | 33,771 |
Purchases in oil and gas reserves in place | MMcf | 371,663 |  | 8,863 |  | 0 |
Extensions and discoveries | MMcf | 997,057 |  | 629,151 |  | 123,597 |
Revisions of prior reserve estimates | MMcf | (371,430) |  | (6,136) |  | (2,031) |
Current production | MMcf | (156,151) |  | (59,318) |  | (8,891) |
End of period |  | 1,560,145 | 719,006 | 719,006 | 146,446 | 146,446
Proved developed reserves | MMcf | 652,961 | 652,961 | 345,166 | 345,166 | 94,552 | 94,552
Proved undeveloped reserves | MMcf | 907,184 | 907,184 | 373,840 | 373,840 | 51,894 | 51,894
Natural Gas Liquids |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  | 26,268 |  | 5,675 |  | 145
Purchases in oil and gas reserves in place |  | 0 |  | 353 |  | 0
Extensions and discoveries |  | 5,486 |  | 22,594 |  | 5,850
Revisions of prior reserve estimates |  | (9,594) |  | (304) |  | 0
Current production |  | (4,424) |  | (2,050) |  | (320)
End of period |  | 17,736 |  | 26,268 |  | 5,675
Proved developed reserves | 12,910 | 12,910 | 12,379 | 12,379 | 3,527 | 3,527
Proved undeveloped reserves | 4,826 | 4,826 | 13,889 | 13,889 | 2,148 | 2,148
Diamondback Energy, Inc | Oil and condensate sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  |  |  | 3,067 |  | 5,606
Change in ownership interest in Diamondback |  |  |  |  |  | (3,720)
Purchases in oil and gas reserves in place |  |  |  |  |  | 528
Extensions and discoveries |  |  |  |  |  | 1,227
Revisions of prior reserve estimates |  |  |  |  |  | (428)
Current production |  |  |  |  |  | (146)
End of period |  |  |  |  |  | 3,067
Proved developed reserves |  |  |  |  | 1,425 | 1,425
Proved undeveloped reserves |  |  |  |  | 1,642 | 1,642
Diamondback Energy, Inc | Natural gas liquids sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period | MMcf |  |  | 4,441 |  | 7,398 |
Change in ownership interest in Diamondback | MMcf |  |  |  |  | (4,909) |
Purchases in oil and gas reserves in place | MMcf |  |  |  |  | 752 |
Extensions and discoveries | MMcf |  |  |  |  | 1,741 |
Revisions of prior reserve estimates | MMcf |  |  |  |  | (417) |
Current production | MMcf |  |  |  |  | (124) |
End of period | MMcf |  |  |  |  | 4,441 |
Proved developed reserves | MMcf |  |  |  |  | 2,263 | 2,263
Proved undeveloped reserves | MMcf |  |  |  |  | 2,178 | 2,178
Diamondback Energy, Inc | Natural Gas Liquids |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  |  |  | 771 |  | 1,766
Change in ownership interest in Diamondback |  |  |  |  |  | (1,171)
Purchases in oil and gas reserves in place |  |  |  |  |  | 120
Extensions and discoveries |  |  |  |  |  | 331
Revisions of prior reserve estimates |  |  |  |  |  | (249)
Current production |  |  |  |  |  | (26)
End of period |  |  |  |  |  | 771
Proved developed reserves |  |  |  |  | 358 | 358
Proved undeveloped reserves |  |  |  |  | 413 | 413
Investment in Grizzly Oil Sands ULC | Oil and condensate sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  | 14,558,000 |  | 13,637,000 |  |
Purchases in oil and gas reserves in place |  | 0 |  | 0 |  |
Extensions and discoveries |  | 0 |  | 0 |  |
Revisions of prior reserve estimates |  | (14,530,000) |  | 990,000 |  |
Current production |  | (28,000) |  | (69,000) |  |
End of period |  | 0 |  | 14,558,000 |  | 13,637,000
Proved developed reserves | 0 | 0 | 2,000 | 2,000 |  |
Proved undeveloped reserves | 0 | 0 | 13,000 | 13,000 |  |
Investment in Grizzly Oil Sands ULC | Natural gas liquids sales |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period | MMcf | 0 |  | 0 |  |  |
Purchases in oil and gas reserves in place | MMcf | 0 |  | 0 |  |  |
Extensions and discoveries | MMcf | 0 |  | 0 |  |  |
Revisions of prior reserve estimates | MMcf | 0 |  | 0 |  |  |
Current production | MMcf | 0 |  | 0 |  |  |
End of period | MMcf | 0 |  | 0 |  | 0 |
Proved developed reserves | MMcf | 0 | 0 | 0 | 0 |  |
Proved undeveloped reserves | MMcf | 0 | 0 | 0 | 0 |  |
Investment in Grizzly Oil Sands ULC | Natural Gas Liquids |  |  |  |  |  |
Proved Developed and Undeveloped Reserves [Roll Forward] |  |  |  |  |  |
Beginning of the period |  | 0 |  | 0 |  |
Purchases in oil and gas reserves in place |  | 0 |  | 0 |  |
Extensions and discoveries |  | 0 |  | 0 |  |
Revisions of prior reserve estimates |  | 0 |  | 0 |  |
Current production |  | 0 |  | 0 |  |
End of period |  | 0 |  | 0 |  | 0
Proved developed reserves | 0 | 0 | 0 | 0 |  |
Proved undeveloped reserves | 0 | 0 | 0 | 0 |  |

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- Definition Additions to proved reserves that result from (1) extension of the proved acreage of previously discovered (old) reservoirs through additional drilling in periods after discovery and (2) discovery of new fields with proved reserves or of new reservoirs of proved reserves in old fields. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=51678428&loc=d3e61831-109447 + Details
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- Definition The net quantity of proved reserves as of the balance sheet date. Proved oil reserves are the estimated quantities of crude oil and natural gas liquids which geological and engineering data demonstrate with reasonable certainty to be recoverable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=51678428&loc=d3e61831-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-10.(a)(2)) -URI http://asc.fasb.org/extlink&oid=50486907&loc=d3e511914-122862 + Details
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