Commodity Price Risk Management (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013 bbl
Current Asset [Member] \| Crude Oil Costless Collars [Member]
Derivatives, Fair Value [Line Items]
Derivative Assets, Fair Value	0
Current Liability [Member] \| Crude Oil Costless Collars [Member]
Derivatives, Fair Value [Line Items]
Derivative Liabilities, Fair Value	145
Crude Oil Costless Collar 10/01/12 - 03/31/13 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	200
Crude Oil Costless Collar 10/01/12 - 03/31/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	85.00
Crude Oil Costless Collar 10/01/12 - 03/31/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	101.00
Crude Oil Costless Collar 01/01/13 - 06/30/13 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	200
Crude Oil Costless Collar 01/01/13 - 06/30/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	90.00
Crude Oil Costless Collar 01/01/13 - 06/30/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	105.75
Crude Oil Costless Collar 04/01/13 - 06/30/13 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	200
Crude Oil Costless Collar 04/01/13 - 06/30/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	90.00
Crude Oil Costless Collar 04/01/13 - 06/30/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	97.50
Crude Oil Costless Collar 10/01/12 - 09/30/13 [Member]
Derivative [Line Items]
Counterparty	BNP Paribas
Basis	WTI
Quantity (barrels per day)	200
Crude Oil Costless Collar 10/01/12 - 09/30/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	95.00
Crude Oil Costless Collar 10/01/12 - 09/30/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	116.60
Crude Oil Costless Collar 07/01/13 - 09/30/13 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	400
Crude Oil Costless Collar 07/01/13 - 09/30/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	90.00
Crude Oil Costless Collar 07/01/13 - 09/30/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	97.50
Crude Oil Costless Collar 10/01/13 - 12/31/13 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	600
Crude Oil Costless Collar 10/01/13 - 12/31/13 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	90.00
Crude Oil Costless Collar 10/01/13 - 12/31/13 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	97.50
Crude Oil Costless Collar 01/01/14 - 06/30/14 [Member]
Derivative [Line Items]
Counterparty	Wells Fargo
Basis	WTI
Quantity (barrels per day)	300
Crude Oil Costless Collar 01/01/14 - 06/30/14 [Member] \| Put Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	90.00
Crude Oil Costless Collar 01/01/14 - 06/30/14 [Member] \| Call Option [Member]
Derivative [Line Items]
Strike Price (in dollars per barrel)	95.00

Identification of the name or type of counterparty to the derivative instrument.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column A

-Footnote 1

+ Details

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Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The quantity per day of future oil and gas production being hedged.

+ References

No definition available.

+ Details

Name:	useg_PortionOfFutureOilAndGasProductionBeingHedgedPerDay
Namespace Prefix:	useg_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

-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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

+ Details

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

- Definition

Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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

- Definition

The strike price on the price risk option contract such as a put option or a call option.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativePriceRiskOptionStrikePrice
Namespace Prefix:	us-gaap_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

- Details

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

- Definition

Reference to the index or unit of measurement for the underlying which establishes the pricing terms of the derivative instrument. For example, the basis on the underlying for a natural gas futures contract might be the NYMEX price per million British thermal units (MMBtu).

+ References

No definition available.

+ Details

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