The cash inflow adjustment related to revenue.

No definition available.

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

- 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

The initial well commitment under the terms of the agreement.

+ References

No definition available.

+ Details

Name:	useg_InitialWellCommitment
Namespace Prefix:	useg_
Data Type:	xbrli:integerItemType
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

Proceeds from the transaction after deduction of payment of the note, commission and other closing costs.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

Name:	useg_NetSalesOfAcres
Namespace Prefix:	useg_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Represent percentage of working interest retained.

+ References

No definition available.

+ Details

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

- Definition

Represent percentage payout of all costs.

+ References

No definition available.

+ Details

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

- 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.

+ References

No definition available.

+ Details

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

- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 30

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

The cash inflow from the sale of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

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

- Details

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

- Details

Name:	dei_LegalEntityAxis=useg_DimmitWoodPropertiesLtdMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=useg_FarmorMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=useg_WilliamsAndMckenzieCountiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=useg_SouthTexasBasedOilAndGasCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementGeographicalAxis=useg_FarmInAcreageMember
Namespace Prefix:
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ACQUISITIONS AND DIVESTITURES (Details) (USD $)	12 Months Ended			0 Months Ended	3 Months Ended
ACQUISITIONS AND DIVESTITURES (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	May 07, 2014 Wells	Jun. 30, 2014	Jan. 21, 2014 acre
Acquisitions and Divestitures [Line Items]
Percentage interest acquired (in hundredths)						50.00%useg_WorkingInterest
Gross acres acquired in acquisition (in acres)						160us-gaap_GasAndOilAreaDevelopedGross
Proceeds from sale of assets held for sale	$ 109,000	$ 2,628,000	$ 76,000
Farm in Acreage [Member]
Acquisitions and Divestitures [Line Items]
Initial well commitment				2
Minimum percentage of net revenue interest in lease owned (in hundredths)				12.50%
South Texas Based Oil and Gas Company [Member]
Acquisitions and Divestitures [Line Items]
Percentage interest acquired (in hundredths)				33.00%
Percentage payout of all costs (in hundredths)				100.00%
Expected net revenue interests in new wells after sale (in hundredths)				115.00%
Cost of acquisition				3,900,000
Dimmit County [Member]
Acquisitions and Divestitures [Line Items]
Percentage interest acquired (in hundredths)	30.00%
Gross acres acquired in acquisition (in acres)	800.77			12,100
Net acres acquired in acquisition (in acres)				3,384
Dimmit County [Member] \| Primary Leasehold Acreage [Member]
Acquisitions and Divestitures [Line Items]
Gross acres acquired in acquisition (in acres)				4,020
Net acres acquired in acquisition (in acres)				1,181
Dimmit County [Member] \| Farm in Acreage [Member]
Acquisitions and Divestitures [Line Items]
Gross acres acquired in acquisition (in acres)				8,080
Net acres acquired in acquisition (in acres)				2,203
Farmor [Member]
Acquisitions and Divestitures [Line Items]
Number of developed wells in which our original working interest is retained				10
Percentage of working interest retained (in hundredths)				25.00%
Williams and McKenzie Counties [Member]
Acquisitions and Divestitures [Line Items]
Gross acres acquired in acquisition (in acres)				16
Net acres acquired in acquisition (in acres)				0.62
Net proceeds on transaction					12,200,000
Adjustment related to revenue					681,000
Proceeds from sale of assets held for sale					$ 11,500,000
Net sales of acres (in acres)				285.70