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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)
 3 Months Ended 12 Months Ended
Dec. 31, 2014
Sep. 30, 2014
Jun. 30, 2014
Mar. 31, 2014
Dec. 31, 2013
Sep. 30, 2013
Jun. 30, 2013
Mar. 31, 2013
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Dec. 31, 2014
Operator
Dec. 31, 2013
Operator
Dec. 31, 2012
Operator
Schedule of Equity Method Investments [Line Items]                              
Impairment of equity investment                         $ 0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment $ 2,160,000us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment $ 0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Marketable Securities [Abstract]                              
Unrealized gains in the marketable securities                         1,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax 45,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax  
Accounts Receivable [Abstract]                              
Bad debt expense                         0us-gaap_ProvisionForDoubtfulAccounts 0us-gaap_ProvisionForDoubtfulAccounts  
Reserve for uncollectable receivables 0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent       0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent               0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent 0us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent  
Valuation of Equity Method Investment [Abstract]                              
Non-cash impairment charge on equity method investment                         0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment 2,160,000us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment 0us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
Revenue Recognition [Abstract]                              
Period of payment received after date of production, minimum                         30 days    
Period of payment received after date of production, maximum                         90 days    
Concentration Risk [Line Items]                              
Number of major operators                         3useg_NumberOfMajorOperators 3useg_NumberOfMajorOperators 2useg_NumberOfMajorOperators
Assumptions [Line Items]                              
Risk free interest rate (in hundredths)                         2.06%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate 1.66%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate  
Expected lives                         6 years 6 years  
Expected volatility (in hundredths)                         65.45%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate 62.59%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate  
Expected dividend yield (in hundredths)                         0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate 0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
Earnings Per Share [Abstract]                              
Shares held by the ESOP (in shares) 949,870us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP       877,399us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP       824,123us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP       949,870us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP 877,399us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP 824,123us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP
Summary of calculations of basic and diluted earnings per share [Abstract]                              
Net (loss) (2,334,000)us-gaap_NetIncomeLoss (63,000)us-gaap_NetIncomeLoss 56,000us-gaap_NetIncomeLoss 250,000us-gaap_NetIncomeLoss (1,220,000)us-gaap_NetIncomeLoss (834,000)us-gaap_NetIncomeLoss 573,000us-gaap_NetIncomeLoss (5,898,000)us-gaap_NetIncomeLoss (7,929,000)us-gaap_NetIncomeLoss (1,945,000)us-gaap_NetIncomeLoss (990,000)us-gaap_NetIncomeLoss (381,000)us-gaap_NetIncomeLoss (2,091,000)us-gaap_NetIncomeLoss (7,379,000)us-gaap_NetIncomeLoss (11,245,000)us-gaap_NetIncomeLoss
Basic weighted-average common shares outstanding (in shares) 27,905,940us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,905,940us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,785,280us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,738,083us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,682,602us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,682,602us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,682,272us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 2,766,710us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,475,813us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,468,355us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,460,483us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,438,584us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,832,859us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,678,698us-gaap_WeightedAverageNumberOfSharesOutstandingBasic 27,466,549us-gaap_WeightedAverageNumberOfSharesOutstandingBasic
Add: dilutive effect of stock options (in shares)                         0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements 0us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements
Diluted weighted-average common shares outstanding (in shares) 27,905,940us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,905,940us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 28,237,883us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 28,142,253us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,682,602us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,682,602us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,682,272us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,667,102us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,475,813us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,468,355us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,460,483us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,438,584us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,832,859us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,678,698us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding 27,466,549us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding
Basic net (loss) per share (in dollars per share) $ (0.08)us-gaap_EarningsPerShareBasic $ 0us-gaap_EarningsPerShareBasic $ 0us-gaap_EarningsPerShareBasic $ 0.01us-gaap_EarningsPerShareBasic $ (0.04)us-gaap_EarningsPerShareBasic $ (0.03)us-gaap_EarningsPerShareBasic $ 0.02us-gaap_EarningsPerShareBasic $ (0.21)us-gaap_EarningsPerShareBasic $ (0.29)us-gaap_EarningsPerShareBasic $ (0.07)us-gaap_EarningsPerShareBasic $ (0.04)us-gaap_EarningsPerShareBasic $ (0.01)us-gaap_EarningsPerShareBasic $ (0.08)us-gaap_EarningsPerShareBasic $ (0.27)us-gaap_EarningsPerShareBasic $ (0.41)us-gaap_EarningsPerShareBasic
Diluted net (loss) per share (in dollars per share) $ (0.08)us-gaap_EarningsPerShareDiluted $ 0us-gaap_EarningsPerShareDiluted $ 0us-gaap_EarningsPerShareDiluted $ 0.01us-gaap_EarningsPerShareDiluted $ (0.04)us-gaap_EarningsPerShareDiluted $ (0.03)us-gaap_EarningsPerShareDiluted $ 0.02us-gaap_EarningsPerShareDiluted $ (0.21)us-gaap_EarningsPerShareDiluted $ (0.29)us-gaap_EarningsPerShareDiluted $ (0.07)us-gaap_EarningsPerShareDiluted $ (0.04)us-gaap_EarningsPerShareDiluted $ (0.01)us-gaap_EarningsPerShareDiluted $ (0.08)us-gaap_EarningsPerShareDiluted $ (0.27)us-gaap_EarningsPerShareDiluted $ (0.41)us-gaap_EarningsPerShareDiluted
Stock Option [Member]                              
Antidilutive securities excluded from computation of earnings per share [Line Items]                              
Weighted-average anti-dilutive stock options (in shares)                         1,355,195us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockOptionMember		 2,531,202us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockOptionMember		 2,491,746us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
/ us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis
= us-gaap_StockOptionMember
Minimum [Member]                              
Assumptions [Line Items]                              
Risk free interest rate, minimum (in hundredths)                             0.82%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Expected lives                             5 years
Expected volatility, minimum (in hundredths)                             61.87%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Maximum [Member]                              
Assumptions [Line Items]                              
Risk free interest rate, maximum (in hundredths)                             1.41%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Expected lives                             6 years
Expected volatility, maximum (in hundredths)                             63.59%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Stock Options [Member]                              
Assumptions [Line Items]                              
Risk free interest rate, minimum (in hundredths)                             0.82%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Risk free interest rate (in hundredths)                         2.06%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		 1.66%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		  
Risk free interest rate, maximum (in hundredths)                             1.41%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected lives                         6 years 6 years  
Expected volatility, minimum (in hundredths)                             61.87%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMinimum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected volatility (in hundredths)                         65.45%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		 62.59%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		  
Expected volatility, maximum (in hundredths)                             63.59%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Expected dividend yield (in hundredths)                         0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember		   0.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
Stock Options [Member] | Minimum [Member]                              
Assumptions [Line Items]                              
Expected lives                             5 years
Stock Options [Member] | Maximum [Member]                              
Assumptions [Line Items]                              
Expected lives                             6 years
Statoil and Zavanna [Member]                              
Concentration Risk [Line Items]                              
Credit risk, percentage (in hundredths)                         28.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_StatoilAndZavannaMember		 38.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_StatoilAndZavannaMember		 57.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_StatoilAndZavannaMember
Contango Oil & Gas [Member]                              
Concentration Risk [Line Items]                              
Credit risk, percentage (in hundredths)                         38.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_ContangoOilGasMember		 32.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_ContangoOilGasMember		  
NGL [Member]                              
Concentration Risk [Line Items]                              
Credit risk, percentage (in hundredths)                         20.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_NglMember		 18.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_NglMember		 32.00%us-gaap_ConcentrationRiskPercentage1
/ dei_LegalEntityAxis
= useg_NglMember
Standard Steam Trust LLC [Member]                              
Schedule of Equity Method Investments [Line Items]                              
Impairment of equity investment                           2,160,000us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= useg_StandardSteamTrustLlcMember		  
Ownership interest (in hundredths) 19.54%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= useg_StandardSteamTrustLlcMember		                       19.54%us-gaap_EquityMethodInvestmentOwnershipPercentage
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= useg_StandardSteamTrustLlcMember		    
Valuation of Equity Method Investment [Abstract]                              
Non-cash impairment charge on equity method investment                           $ 2,160,000us-gaap_EquityMethodInvestmentOtherThanTemporaryImpairment
/ us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis
= useg_StandardSteamTrustLlcMember