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SHAREHOLDERS' EQUITY (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Weighted Average Exercise Price [Roll Forward]      
Value of stock options exercised $ (62,000)us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised   $ 0us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of outstanding shares reserved for issuance (in hundredths) 25.00%useg_PercentageOfOutstandingSharesReservedForIssuance
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
   
Shares reserved for authorization (in shares) 1,200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
   
Number of options available for grant and intrinsic value of options outstanding and exercisable [Abstract]      
Available for future grant (in shares) 790,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
790,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
1,060,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
Aggregate intrinsic value of options outstanding 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
1,661,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
Aggregate intrinsic value of options exercisable 0us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
1,073,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
0us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
Employee Stock Options [Member]      
Options [Roll Forward]      
Outstanding at beginning of the year (in shares) 2,500,949us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,259,282us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,318,399us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Granted (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
270,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
150,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Forfeited (in shares) (3,333)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
(10,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Expired (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
(28,333)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
(194,950)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in shares) (400,203)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
(4,167)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Outstanding at period end (in shares) 2,097,413us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,500,949us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,259,282us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercisable at year end (in shares) 1,949,080us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,137,619us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
2,119,282us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Weighted Average Exercise Price [Roll Forward]      
Beginning Balance (in dollars per share) $ 3.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.94us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Granted (in dollars per share) $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 2.08us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 2.32us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Forfeited (in dollars per share) $ 2.08us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 2.32us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Expired (in dollar per share) $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 4.68us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 4.47us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercised (in dollars per share) $ 2.46us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 2.52us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Ending Balance (in dollars per share) $ 3.82us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.60us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.80us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Exercisable (in dollars per share) $ 3.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 3.90us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Weighted average fair value of options granted during the period (in dollars per share) $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 1.20us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
$ 1.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Employee Stock Options [Member] | Stock Options [Member]      
Weighted Average Exercise Price [Roll Forward]      
Proceeds from stock options exercised 1,000us-gaap_ProceedsFromStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
   
Withholding of shares (in shares) 14,206useg_StockWithholdingOfSharesDuringPeriod
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
   
Withhold values of common stock 63,000useg_WithholdValuesOfCommonStock
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
   
Shares surrendered upon stock option exercise (in shares) 228,047us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
  3,097us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Value of stock options exercised 982,000us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
  10,000us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Intrinsic value of option exercised 743,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
4,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Share-based compensation expense 229,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
120,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
33,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
Total unrecognized expense for the option plan 124,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= us-gaap_EmployeeStockOptionMember
   
Director Stock Options [Member]      
Options [Roll Forward]      
Outstanding at beginning of the year (in shares) 146,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
150,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
210,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Granted (in shares) 60,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
36,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
80,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Forfeited (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Expired (in shares) 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
(40,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
(120,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Exercised (in shares) (27,334)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
0us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
(20,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Outstanding at period end (in shares) 178,666us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
146,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
150,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Exercisable at year end (in shares) 82,333us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
56,668us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
63,335us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Weighted Average Exercise Price [Roll Forward]      
Beginning Balance (in dollars per share) $ 2.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.10us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Granted (in dollars per share) $ 3.77us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 2.08us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 2.78us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Forfeited (in dollars per share) $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Expired (in dollar per share) $ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 2.60us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.05us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Exercised (in dollars per share) $ 2.53us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 0us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 2.52us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Ending Balance (in dollars per share) $ 3.28us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 2.93us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.05us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Exercisable (in dollars per share) $ 3.30us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.46us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 3.01us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Weighted average fair value of options granted during the period (in dollars per share) $ 2.27us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 1.20us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 1.59us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Director Stock Options [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percentage of common stock (in hundredths) 1.00%us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
   
Weighted Average Exercise Price [Roll Forward]      
Proceeds from stock options exercised 8,000us-gaap_ProceedsFromStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
50,000us-gaap_ProceedsFromStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
 
Shares surrendered upon stock option exercise (in shares) 15,000us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
   
Value of stock options exercised 61,000us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
   
Intrinsic value of option exercised 45,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
17,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Share-based compensation expense 89,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
64,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
69,000us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Total unrecognized expense for the option plan 147,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
   
Number of options available for grant and intrinsic value of options outstanding and exercisable [Abstract]      
Available for future grant (in shares) 101,811us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
131,359us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
126,526us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Aggregate intrinsic value of options outstanding 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
142,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
Aggregate intrinsic value of options exercisable $ 0us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 35,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
$ 0us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= useg_StockOption1Member
/ us-gaap_PlanNameAxis
= useg_DirectorStockOptionMember
2001 Incentive Stock Option Plan [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Term of the plan 10 years    
2012 Equity Plan [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Term of the plan 10 years    
2008 Stock Option Plan [Member] | Stock Options [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Term of the plan 10 years