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Summary of Significant Accounting Policies (Details) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Center
Mar. 31, 2014
Dec. 31, 2014
Jan. 21, 2014
acre
Properties and Equipment [Abstract]        
Property, plant and equipment $ 8,320,000us-gaap_PropertyPlantAndEquipmentOther   $ 8,346,000us-gaap_PropertyPlantAndEquipmentOther  
Less accumulated depreciation (4,441,000)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment   (4,404,000)us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment  
Net book value 3,879,000us-gaap_PropertyPlantAndEquipmentOtherNet   3,942,000us-gaap_PropertyPlantAndEquipmentOtherNet  
Oil and Gas Properties [Abstract]        
Capitalized costs excluded from amortized cost pool 9,600,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative   12,500,000us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationCumulative  
Capitalized costs related to unevaluated properties included in the amortization base 0useg_CapitalizedCostsOfUnevaluatedPropertyIncludedInAmortizationBase   0useg_CapitalizedCostsOfUnevaluatedPropertyIncludedInAmortizationBase  
Percentage of discount used for future net revenue (in hundredths) 10.00%useg_PercentageOfDiscountUsedForFutureNetRevenue      
Period for calculating unescalated average prices prior to the end of reporting period 12 months      
Number of cost centers for quarterly ceiling test for oil and gas 1useg_NumberOfCostCentersForQuarterlyCeilingTestForOilAndGas      
Price per barrel for oil at ceiling test 82.72useg_PricePerBarrelForOilAtCeilingTest      
Price for natural gas at ceiling test 3.882useg_PricePerBarrelForNaturalGasAtCeilingTest      
Proved property impairments 19,240,000us-gaap_ImpairmentOfOilAndGasProperties 0us-gaap_ImpairmentOfOilAndGasProperties    
Mineral Properties [Abstract]        
Costs associated with Mount Emmons beginning of year 21,942,000us-gaap_MineralPropertiesNet 20,739,000us-gaap_MineralPropertiesNet 20,739,000us-gaap_MineralPropertiesNet  
Property purchase 0us-gaap_AcquisitionCosts [1]   1,203,000us-gaap_AcquisitionCosts [1]  
Costs at the end of the period $ 21,942,000us-gaap_MineralPropertiesNet   $ 21,942,000us-gaap_MineralPropertiesNet  
Percentage interest acquired (in hundredths)       50.00%useg_WorkingInterest
Acres acquired       160us-gaap_GasAndOilAreaDevelopedGross
Minimum [Member]        
Property, Plant and Equipment [Line Items]        
Estimated useful lives 3 years      
Maximum [Member]        
Property, Plant and Equipment [Line Items]        
Estimated useful lives 45 years      
[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.