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ACQUISITIONS AND DIVESTITURES (Details) (USD $) | 12 Months Ended | 0 Months Ended | 3 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | May 07, 2014 Wells | Jun. 30, 2014 | Jan. 21, 2014 acre
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Percentage interest acquired (in hundredths) |  |  |  |  |  | 50.00%useg_WorkingInterest
Gross acres acquired in acquisition (in acres) |  |  |  |  |  | 160 us-gaap_GasAndOilAreaDevelopedGross
Proceeds from sale of assets held for sale | $ 109,000 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment | $ 2,628,000 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment | $ 76,000 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment |  |  |
Farm in Acreage [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Initial well commitment |  |  |  | 2 useg_InitialWellCommitment / us-gaap_StatementGeographicalAxis = useg_FarmInAcreageMember |  |
Minimum percentage of net revenue interest in lease owned (in hundredths) |  |  |  | 12.50%useg_MinimumPercentageOfNetRevenueInterestInLeasesOwned / us-gaap_StatementGeographicalAxis = useg_FarmInAcreageMember |  |
South Texas Based Oil and Gas Company [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Percentage interest acquired (in hundredths) |  |  |  | 33.00%useg_WorkingInterest / us-gaap_BusinessAcquisitionAxis = useg_SouthTexasBasedOilAndGasCompanyMember |  |
Percentage payout of all costs (in hundredths) |  |  |  | 100.00%useg_PercentagePayoutOfAllCosts / us-gaap_BusinessAcquisitionAxis = useg_SouthTexasBasedOilAndGasCompanyMember |  |
Expected net revenue interests in new wells after sale (in hundredths) |  |  |  | 115.00%useg_ExpectedNetRevenueInterestsInNewWellsAfterSale / us-gaap_BusinessAcquisitionAxis = useg_SouthTexasBasedOilAndGasCompanyMember |  |
Cost of acquisition |  |  |  | 3,900,000 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = useg_SouthTexasBasedOilAndGasCompanyMember |  |
Dimmit County [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Percentage interest acquired (in hundredths) | 30.00%useg_WorkingInterest / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember |  |  |  |  |
Gross acres acquired in acquisition (in acres) | 800.77 us-gaap_GasAndOilAreaDevelopedGross / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember |  |  | 12,100 us-gaap_GasAndOilAreaDevelopedGross / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember |  |
Net acres acquired in acquisition (in acres) |  |  |  | 3,384 us-gaap_GasAndOilAreaDevelopedNet / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember |  |
Dimmit County [Member] | Primary Leasehold Acreage [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Gross acres acquired in acquisition (in acres) |  |  |  | 4,020 us-gaap_GasAndOilAreaDevelopedGross / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember / us-gaap_StatementGeographicalAxis = useg_PrimaryLeaseholdAcreageMember |  |
Net acres acquired in acquisition (in acres) |  |  |  | 1,181 us-gaap_GasAndOilAreaDevelopedNet / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember / us-gaap_StatementGeographicalAxis = useg_PrimaryLeaseholdAcreageMember |  |
Dimmit County [Member] | Farm in Acreage [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Gross acres acquired in acquisition (in acres) |  |  |  | 8,080 us-gaap_GasAndOilAreaDevelopedGross / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember / us-gaap_StatementGeographicalAxis = useg_FarmInAcreageMember |  |
Net acres acquired in acquisition (in acres) |  |  |  | 2,203 us-gaap_GasAndOilAreaDevelopedNet / dei_LegalEntityAxis = useg_DimmitWoodPropertiesLtdMember / us-gaap_StatementGeographicalAxis = useg_FarmInAcreageMember |  |
Farmor [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Number of developed wells in which our original working interest is retained |  |  |  | 10 us-gaap_ProductiveOilWellsNumberOfWellsGross / dei_LegalEntityAxis = useg_FarmorMember |  |
Percentage of working interest retained (in hundredths) |  |  |  | 25.00%useg_PercentageOfWorkingInterestRetained / dei_LegalEntityAxis = useg_FarmorMember |  |
Williams and McKenzie Counties [Member] |  |  |  |  |  |
Acquisitions and Divestitures [Line Items] |  |  |  |  |  |
Gross acres acquired in acquisition (in acres) |  |  |  | 16 us-gaap_GasAndOilAreaDevelopedGross / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |  |
Net acres acquired in acquisition (in acres) |  |  |  | 0.62 us-gaap_GasAndOilAreaDevelopedNet / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |  |
Net proceeds on transaction |  |  |  |  | 12,200,000 useg_NetProceedsOnTransaction / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |
Adjustment related to revenue |  |  |  |  | 681,000 useg_AdjustmentRelatedToRevenue / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |
Proceeds from sale of assets held for sale |  |  |  |  | $ 11,500,000 us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |
Net sales of acres (in acres) |  |  |  | 285.70 useg_NetSalesOfAcres / dei_LegalEntityAxis = useg_WilliamsAndMckenzieCountiesMember |  |

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