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Supplemental Information On Oil And Gas Exploration And Production Activities (Unaudited) (Changes in Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves) (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | $ (486,185) | $ (530,098) | $ (197,559)
Net changes in prices, production costs, and development costs | (1,412,181) | 97,716 | 65,573
Acquisition of oil and gas reserves in place | 83,340 | 14,266 | 0
Extensions and discoveries | 262,895 | 790,533 | 130,826
Previously estimated development costs incurred during the period | 117,540 | 68,227 | 43,478
Revisions of previous quantity estimates, less related production costs | (98,162) | (37,801) | (3,591)
Accretion of discount | 142,717 | 57,847 | 34,864
Net changes in income taxes | 412,240 | (295,226) | (30,239)
Change in production rates and other | 314,960 | 683,237 | 186,473
Total change in standardized measure of discounted future net cash flows | (662,836) | 848,701 | 229,825
Diamondback Energy, Inc |  |  |
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | 0 | 0 | (12,524)
Change in ownership interest in Diamondback | 0 | 0 | (52,145)
Net changes in prices, production costs, and development costs | 0 | 0 | 3,312
Acquisition of oil and gas reserves in place | 0 | 0 | 21,968
Extensions and discoveries | 0 | 0 | 39,776
Previously estimated development costs incurred during the period | 0 | 0 | 5,517
Revisions of previous quantity estimates, less related production costs | 0 | 0 | (9,143)
Accretion of discount | 0 | 0 | 4,175
Net changes in income taxes | 0 | 0 | (12,137)
Change in production rates and other | 0 | 0 | 2,862
Total change in standardized measure of discounted future net cash flows | 0 | 0 | (8,339)
Investment in Grizzly Oil Sands ULC |  |  |
Changes In Standardized Measure of Discontinued Future Net Cash Flows [Line Items] |  |  |
Sales and transfers of oil and gas produced, net of production costs | 114 | 4,664 | 0
Net changes in prices, production costs, and development costs | 0 | (76,518) | 0
Acquisition of oil and gas reserves in place | 0 | 0 | 0
Extensions and discoveries | 0 | 7,107 | 0
Previously estimated development costs incurred during the period | 47 | 0 | 0
Revisions of previous quantity estimates, less related production costs | (103,282) | 10,659 | 0
Accretion of discount | 9,375 | 14,946 | 0
Net changes in income taxes | 0 | 9,162 | 0
Change in production rates and other | 0 | (25,738) | 0
Total change in standardized measure of discounted future net cash flows | $ (93,746) | $ (55,718) | $ 0

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