Mineral Property Transactions (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2012
Gas and Oil Acreage [Line Items]
Number of Projects	7
Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Percentage of undeveloped acreage sold (in hundredths)	75.00%
Proceeds from sale of undeveloped acreage	16.7
Proceeds from reimbursed well costs	1.4
Transfer of costs from unevaluated properties to proved properties	5.3
Percentage of interest in undeveloped acreage retained (in hundredths)	25.00%
Number of developed wells in which our original working interest is retained	10
Percentage of average working interest in the remaining locations (in hundredths)	8.75%
Purchase price of Woodbine acquisition	2.3
Number of formation wells in which interest acquired	27
Number of drilling units in which interest acquired	23
Production per day, barrels of oil equivalents	47
Woodbine [Member]
Gas and Oil Acreage [Line Items]
Percentage of initial working interest (in hundredths)	26.50%
Percentage of net revenue interest (in hundredths)	19.60%
Reduced percentage of net revenue interests after payout of initial well cost (in hundredths)	14.70%
Reduced percentage of working interests after payout of initial well cost (in hundredths)	19.80%
Gross acres acquired in Woodbine acquisition (in acres)	6,766
Net acres acquired in Woodbine acquisition (in acres)	1,274
Purchase price of Woodbine acquisition	1.7
Montana Acreage [Member]
Gas and Oil Acreage [Line Items]
Percentage of undeveloped acreage sold (in hundredths)	87.50%
Proceeds from sale of undeveloped acreage	3.7
Transfer of costs from unevaluated properties to proved properties	1.0
Percentage of interest in undeveloped acreage retained (in hundredths)	12.50%
Minimum percentage of net revenue interest in lease owned (in hundredths)	81.00%
Percentage of net revenue interest delivered to purchaser (in hundredths)	80.00%
Percentage of overriding royalty interest delivered to land broker (in hundredths)	1.00%
Percentage of commission paid to land broker (in hundredths)	10.00%
Minimum [Member] \| Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Expected net revenue interests in new wells after sale (in hundredths)	6.7375%
Percentage of initial working interest (in hundredths)	1.00%
Maximum [Member] \| Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Expected net revenue interests in new wells after sale (in hundredths)	7.00%
Percentage of initial working interest (in hundredths)	5.00%
Weighted Average [Member] \| Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Percentage of initial working interest (in hundredths)	1.45%
GeoResources, Inc [Member] \| Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Percentage of undeveloped acreage sold (in hundredths)	(56.25%)
Yuma Exploration and Production Company, Inc [Member] \| Bakken and Three Forks [Member]
Gas and Oil Acreage [Line Items]
Percentage of undeveloped acreage sold (in hundredths)	(18.75%)

Percentage of net revenue interests acquired in the business combination.

No definition available.

Name:	useg_BusinessAcquisitionPercentageOfNetRevenueInterestsAcquired
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the expected net revenue interests in new wells after sale.

+ References

No definition available.

+ Details

Name:	useg_ExpectedNetRevenueInterestsInNewWellsAfterSale
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represent the minimum percentage of net revenue interest in lease owned as per the agreement.

+ References

No definition available.

+ Details

Name:	useg_MinimumPercentageOfNetRevenueInterestInLeasesOwned
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This line item represents the number of drilling units for mineral property transactions.

+ References

No definition available.

+ Details

Name:	useg_NumberOfDrillingUnitsInWhichInterestAcquired
Namespace Prefix:	useg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

This line item represents the number of formation wells in which interest is acquired by the reporting entity.

+ References

No definition available.

+ Details

Name:	useg_NumberOfFormationWellsInWhichInterestAcquired
Namespace Prefix:	useg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the number of projects.

+ References

No definition available.

+ Details

Name:	useg_NumberOfProjects
Namespace Prefix:	useg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of acreage sold.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfAcreageSold
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of average working interest in the remaining locations.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfAverageWorkingInterestInRemainingLocations
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of commission paid to the land broker for the cash consideration paid by purchaser.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfCommissionPaidToLandBroker
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of interest in acreage retained.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfInterestInAcreageRetained
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of net revenue interest delivered to purchaser.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfNetRevenueInterestDeliveredToPurchaser
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of overriding royalty interest delivered to land broker.

+ References

No definition available.

+ Details

Name:	useg_PercentageOfOverridingRoyaltyInterestDeliveredToLandBroker
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow from reimbursed well costs.

+ References

No definition available.

+ Details

Name:	useg_ProceedsFromReimbursedWellCosts
Namespace Prefix:	useg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The cash inflow from sale of undeveloped acreage.

+ References

No definition available.

+ Details

Name:	useg_ProceedsFromSaleOfUndevelopedAcreage
Namespace Prefix:	useg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the reduced percentage of net revenue interests after payout of initial well cost.

+ References

No definition available.

+ Details

Name:	useg_ReducedPercentageOfNetRevenueInterestsAfterPayoutOfInitialWellCost
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the reduced percentage of working interests after payout of initial well cost.

+ References

No definition available.

+ Details

Name:	useg_ReducedPercentageOfWorkingInterestsAfterPayoutOfInitialWellCost
Namespace Prefix:	useg_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of transfer of costs from unevaluated properties to proved properties.

+ References

No definition available.

+ Details

Name:	useg_TransferOfCostsFromUnevaluatedPropertiesToProvedProperties
Namespace Prefix:	useg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 51

-Subparagraph d

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Name:	us-gaap_BusinessAcquisitionCostOfAcquiredEntityPurchasePrice
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of voting equity interests acquired in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7659399&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_GasAndOilAcreageLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_GasAndOilAreaDevelopedGross
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Fractional interest owned based on working interests or other economic arrangements of area spaced or assigned to productive wells.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 4

-Subparagraph A

+ Details

Name:	us-gaap_GasAndOilAreaDevelopedNet
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

This element represents the number of barrel of oil equivalents (BOE) which is a measurement used by oil and gas companies as a way of combining oil and natural gas reserves and production into a single measurement. Natural gas volumes are converted to BOE based on the energy content of 6,000 cubic feet of gas to one barrel of oil.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Industry Guide

-Number 2

-Paragraph 3

-Subparagraph A

+ Details

Name:	us-gaap_ProductionBarrelsOfOilEquivalents
Namespace Prefix:	us-gaap_
Data Type:	us-types:boeItemType
Balance Type:	na
Period Type:	duration

- Definition

The total number of producing oil wells and oil wells capable of production, in which the entity owns an undivided working interest.

+ 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant