Subsequent Events (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	9 Months Ended
Oct. 06, 2011	Sep. 30, 2011
Senior Credit Facility Details [Abstract]
Revolving Bank Loan Comitment Value	$ 1,000	$ 500
Max Revolving Bank Loan Comitment Value	1,250	750
Letter Of Credit Commitment Credit Facility	$ 250.0
Debt Instrument Interest Rate Terms Prime	0.50%	0.50%
Debt Instrument Interest Rate Terms Libor	1.75%	1.25%
Line of Credit Facility, Covenant Terms		The 2007 Credit Agreement had restrictive covenants that included the maintenance of a ratio of consolidated funded debt to EBITDAX (earnings before interest, taxes, DD&A and other non-cash charges) not to exceed three and one half times; and as long as the Company’s debt rating was below investment grade, the maintenance of an annual ratio of the net present value of the Company’s oil and gas properties to total funded debt of at least 1.75 to 1.00.

Description of the interest rate as being variable and identification of the LIBOR index as the rate on which the interest is based and the number of points or percentage added to that index or rate to set the rate.

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- Definition

Description of the interest rate as being variable and identification of the Prime index as the rate on which the interest is based and the number of points or percentage added to that index or rate to set the rate.

+ Details

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- Definition

Represents the commitment under the 2011 Credit Agreement for the issuance of letters of credit.

+ Details

Name:	upl_LetterOfCreditCommitmentCreditFacility
Namespace Prefix:	upl
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum aggregate commitment available under the current revolving credit facility.

+ Details

Name:	upl_MaxRevolvingBankLoanComitmentValue
Namespace Prefix:	upl
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Initial loan commitment for revolving credit facility.

+ Details

Name:	upl_RevolvingBankLoanComitmentValue
Namespace Prefix:	upl
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	upl_SeniorCreditFacilityDetailsAbstract
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- Definition

Description of the conditions for borrowing under the credit facility including the nature of any restrictions.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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