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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	$ 20,739us-gaap_MineralPropertiesNet
Property purchase	3,732us-gaap_AcquisitionCosts		2,067us-gaap_AcquisitionCosts		271us-gaap_AcquisitionCosts	4,015us-gaap_AcquisitionCosts	103us-gaap_AcquisitionCosts
Costs at the end of the period	21,942us-gaap_MineralPropertiesNet		20,739us-gaap_MineralPropertiesNet
Percentage interest acquired (in hundredths)								50.00%useg_WorkingInterest
Acres acquired								160us-gaap_GasAndOilAreaDevelopedGross
Reconciliation of total liability for asset retirement obligations [Roll Forward]
Beginning asset retirement obligation	812us-gaap_AssetRetirementObligation		686us-gaap_AssetRetirementObligation
Accretion of discount	40us-gaap_AssetRetirementObligationAccretionExpense		38us-gaap_AssetRetirementObligationAccretionExpense
Liabilities incurred	310us-gaap_AssetRetirementObligationLiabilitiesIncurred		131us-gaap_AssetRetirementObligationLiabilitiesIncurred
Liabilities settled	(29)us-gaap_AssetRetirementObligationLiabilitiesSettled		(43)us-gaap_AssetRetirementObligationLiabilitiesSettled
Ending asset retirement obligation	1,133us-gaap_AssetRetirementObligation		812us-gaap_AssetRetirementObligation		686us-gaap_AssetRetirementObligation
Mt. Emmons Property [Member]
Mineral Properties [Abstract]
Costs associated with Mount Emmons beginning of year	20,739us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember		20,739us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember
Property purchase	1,203us-gaap_AcquisitionCosts / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember	[1]	0us-gaap_AcquisitionCosts / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember	[1]
Costs at the end of the period	21,942us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember		20,739us-gaap_MineralPropertiesNet / useg_ProjectAxis = us-gaap_UncompletedWellsEquipmentAndFacilitiesMember
Mining Properties [Member]
Reconciliation of total liability for asset retirement obligations [Roll Forward]
Ending asset retirement obligation	187us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_MiningPropertiesAndMineralRightsMember		175us-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	$ 946us-gaap_AssetRetirementObligation / useg_ProjectAxis = us-gaap_OilAndGasPropertiesMember		$ 637us-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.

X

- 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.

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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.

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Area spaced or assigned to productive wells in which a working interest is owned.

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Mineral properties, net of adjustments.

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