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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES, MINERAL PROPERTIES (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2010 | Jan. 21, 2014 acre
Mineral Properties [Abstract] |  |  |  |  |  |  |  |
Costs associated with Mount Emmons beginning of year | $ 20,739 us-gaap_MineralPropertiesNet |  |  |  |  |  |  |
Property purchase | 3,732 us-gaap_AcquisitionCosts |  | 2,067 us-gaap_AcquisitionCosts |  | 271 us-gaap_AcquisitionCosts | 4,015 us-gaap_AcquisitionCosts | 103 us-gaap_AcquisitionCosts |
Costs at the end of the period | 21,942 us-gaap_MineralPropertiesNet |  | 20,739 us-gaap_MineralPropertiesNet |  |  |  |  |
Percentage interest acquired (in hundredths) |  |  |  |  |  |  |  | 50.00%useg_WorkingInterest
Acres acquired |  |  |  |  |  |  |  | 160 us-gaap_GasAndOilAreaDevelopedGross
Reconciliation of total liability for asset retirement obligations [Roll Forward] |  |  |  |  |  |  |  |
Beginning asset retirement obligation | 812 us-gaap_AssetRetirementObligation |  | 686 us-gaap_AssetRetirementObligation |  |  |  |  |
Accretion of discount | 40 us-gaap_AssetRetirementObligationAccretionExpense |  | 38 us-gaap_AssetRetirementObligationAccretionExpense |  |  |  |  |
Liabilities incurred | 310 us-gaap_AssetRetirementObligationLiabilitiesIncurred |  | 131 us-gaap_AssetRetirementObligationLiabilitiesIncurred |  |  |  |  |
Liabilities settled | (29)us-gaap_AssetRetirementObligationLiabilitiesSettled |  | (43)us-gaap_AssetRetirementObligationLiabilitiesSettled |  |  |  |  |
Ending asset retirement obligation | 1,133 us-gaap_AssetRetirementObligation |  | 812 us-gaap_AssetRetirementObligation |  | 686 us-gaap_AssetRetirementObligation |  |  |
Mt. Emmons Property [Member] |  |  |  |  |  |  |  |
Mineral Properties [Abstract] |  |  |  |  |  |  |  |
Costs associated with Mount Emmons beginning of year | 20,739 us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember |  | 20,739 us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember |  |  |  |  |
Property purchase | 1,203 us-gaap_AcquisitionCosts / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember | [1] | 0 us-gaap_AcquisitionCosts / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember | [1] |  |  |  |
Costs at the end of the period | 21,942 us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember |  | 20,739 us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember |  |  |  |  |
Mining Properties [Member] |  |  |  |  |  |  |  |
Reconciliation of total liability for asset retirement obligations [Roll Forward] |  |  |  |  |  |  |  |
Ending asset retirement obligation | 187 us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_MiningPropertiesAndMineralRightsMember |  | 175 us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_MiningPropertiesAndMineralRightsMember |  |  |  |  |
Oil and Gas Wells [Member] |  |  |  |  |  |  |  |
Reconciliation of total liability for asset retirement obligations [Roll Forward] |  |  |  |  |  |  |  |
Ending asset retirement obligation | $ 946 us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_OilAndGasPropertiesMember |  | $ 637 us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_OilAndGasPropertiesMember |  |  |  |  |
[1] | On January 21, 2014, the Company acquired Thompson Creek Metals' ("TCM") 50% interest in 160 acres of fee land in the vicinity of the Mt. Emmons project mining claims for $1.2 million. The property was originally acquired jointly by the Company and TCM in January 2009.

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- Definition A percentage of ownership in an oil and gas lease granting its owner the right to explore, drill and produce oil and gas from a tract of property. Working interest owners are obligated to pay a corresponding percentage of the cost of leasing, drilling, producing and operating a well or unit. After royalties are paid, the working interest also entitles its owner to share in production revenues with other working interest owners, based on the percentage of working interest owned. + References No definition available. + Details
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- Definition The capitalized costs incurred during the period (excluded from amortization) to purchase, lease or otherwise acquire an unproved property, including costs of lease bonuses and options to purchase or lease properties, the portion of costs applicable to minerals when land including mineral rights is purchased in fee, brokers' fees, recording fees, legal costs, and other costs incurred in acquiring properties. + References Reference 1: 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.(c)(7)(ii)) -URI http://asc.fasb.org/extlink&oid=27015464&loc=d3e511914-122862 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 10 -Paragraph c -Subparagraph 3(ii)(A) -Article 4 + Details
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- Definition Amount of accretion expense recognized during the period that is associated with an asset retirement obligation. Accretion expense measures and incorporates changes due to the passage of time into the carrying amount of the liability. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6392676&loc=d3e7480-110848 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 + Details
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- Definition Area spaced or assigned to productive wells in which a working interest is owned. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Industry Guide -Number 2 -Paragraph 4 -Subparagraph A + Details
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- Definition Mineral properties, net of adjustments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 932 -SubTopic 360 -Section 25 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6474861&loc=d3e64895-109465 + Details
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