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v2.4.1.9

Supplemental Information on Oil and Natural Gas Producing Activities - Summary of Changes in Estimated Oil and Natural Gas Reserves (Unaudited) (Details) | 12 Months Ended |
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Dec. 31, 2014 MBbls | Dec. 31, 2013 MBbls | Dec. 31, 2012 MBbls | Dec. 31, 2011 MBbls
Oil Reserves |  |  |  |  |  |  |  |
Proved Developed and Undeveloped Reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) |  |  |  |  |  |  |  |
Proved developed and undeveloped reserves, beginning balance | 142,641 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | [1] | 262,045 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | [1] | 214,450 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Revisions of previous estimates | (18,687)us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (13,969)us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (37,394)us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Acquisitions of new reserves | 1,009 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 43 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 31,470 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Extensions and discoveries | 37,603 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 40,570 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 89,656 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Sales of reserves in place | (25,659)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (131,769)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (20,269)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Production | (10,876)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (14,279)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | (15,868)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  |  |
Proved developed and undeveloped reserves, ending balance | 126,031 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | [1] | 142,641 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | [1] | 262,045 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember | [1] |  |
Proved developed reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 79,022 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 83,893 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 136,605 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 101,578 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |
Proved undeveloped reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 47,009 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 58,748 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 125,440 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |  | 112,872 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember |
Natural Gas Liquids |  |  |  |  |  |  |  |
Proved Developed and Undeveloped Reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) |  |  |  |  |  |  |  |
Proved developed and undeveloped reserves, beginning balance | 59,052 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | [1] | 67,994 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | [1] | 30,335 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Revisions of previous estimates | 11,103 us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 3,717 us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 15,098 us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Acquisitions of new reserves | 441 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 13 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 683 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Extensions and discoveries | 27,500 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 18,686 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 27,259 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Sales of reserves in place | (2,516)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | (29,067)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | (3,287)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Production | (3,794)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | (2,291)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | (2,094)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  |  |
Proved developed and undeveloped reserves, ending balance | 91,786 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | [1] | 59,052 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | [1] | 67,994 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember | [1] |  |
Proved developed reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 56,823 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 35,807 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 33,785 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 17,150 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |
Proved undeveloped reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 34,963 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 23,245 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 34,209 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |  | 13,185 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember |
Natural Gas |  |  |  |  |  |  |  |
Proved Developed and Undeveloped Reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) |  |  |  |  |  |  |  |
Proved developed and undeveloped reserves, beginning balance | 1,390,429 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [1],[2] | 1,415,042 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [1],[2] | 1,355,056 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Revisions of previous estimates | 167,589 us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (53,432)us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (538,214)us-gaap_ProvedDevelopedAndUndevelopedReservesRevisionsOfPreviousEstimatesIncreaseDecrease / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Acquisitions of new reserves | 12,527 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 363 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 202,995 us-gaap_ProvedDevelopedAndUndevelopedReservesPurchasesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Extensions and discoveries | 467,185 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 359,918 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 489,302 us-gaap_ProvedDevelopedAndUndevelopedReservesExtensionsDiscoveriesAndAdditions / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Sales of reserves in place | (163,800)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (228,229)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (548)us-gaap_ProvedDevelopedAndUndevelopedReservesSalesOfMineralsInPlace / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Production | (85,697)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (103,233)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | (93,549)us-gaap_ProvedDevelopedAndUndevelopedReservesProduction / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] |  |
Proved developed and undeveloped reserves, ending balance | 1,788,233 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [1],[2] | 1,390,429 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [1],[2] | 1,415,042 us-gaap_ProvedDevelopedAndUndevelopedReservesNet / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [1],[2] |  |
Proved developed reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 1,203,447 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 951,609 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 896,701 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 670,382 us-gaap_ProvedDevelopedReservesVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2]
Proved undeveloped reserves (in MBbls for Oil and NGLs/MMcf for Natural Gas) | 584,786 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 438,820 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 518,341 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2] | 684,674 us-gaap_ProvedUndevelopedReserveVolume / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember | [2]
[1] | Includes proved reserves attributable to noncontrolling interests at December 31, 2014, 2013 and 2012 as shown in the table below: December 31, 2014 2013 2012Oil (MBbl)11,027 13,569 17,340NGL (MBbl)4,761 4,737 5,132Natural gas (MMcf)70,833 69,693 94,543
[2] | Natural gas reserves are computed at 14.65 pounds per square inch absolute and 60 degrees Fahrenheit.

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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=8451039&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=8451039&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=27015464&loc=d3e511914-122862 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph a -Subparagraph 2 -Article 4 + Details
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- Definition Net quantities of an enterprise's interests in proved developed reserves of either crude oil (including condensate and natural gas liquids), natural gas, synthetic oil and gas, or other nonrenewable natural resource that is intended to be upgraded into synthetic oil and gas as of the beginning and the end of the year. "Net" quantities of reserves include those relating to the enterprise's operating and nonoperating interests in properties. Quantities of reserves relating to royalty interests owned are included in "net" quantities if the necessary information is available to the enterprise. "Net" quantities does not include reserves relating to interests of others in properties owned by the enterprise. The unit of measure for reserve quantities is defined as "barrels" for oil and synthetic oil reserves or "cubic feet" or "cubic meters" for natural gas and synthetic gas reserves. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61797-109447 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 235 -Section 50 -Paragraph 9 -URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e61884-109447 + Details
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