Debt and Other Long Term Liabilities (Details Textuals) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Senior Credit Facility Details [Abstract]
Revolving Bank Loan Comitment Value	$ 1,000,000,000upl_RevolvingBankLoanComitmentValue
Max Revolving Bank Loan Comitment Value	1,250,000,000upl_MaxRevolvingBankLoanComitmentValue
Letters Of Credit Availability	250,000,000upl_LettersOfCreditAvailability
Bank indebtedness	518,000,000us-gaap_NotesPayableToBank	460,000,000us-gaap_NotesPayableToBank
Credit Facility Lender Consent Requirement	50.00%
Available borrowing capacity	482,000,000
Debt Instrument Interest Rate Terms Prime	100
Debt Instrument Interest Rate Terms Libor	200
Commitment fees incurred in current year	2,000,000
Ultra Resources Inc Senior Notes
Senior Notes Ultra Resources Inc	1,560,000,000upl_SeniorNotesUltraResourcesInc
Ultra Petroleum Corp Senior Notes
Senior Notes Ultra Petroleum Corp Due 2024	850,000,000
Senior Notes Ultra Petroleum Corp Due 2024 Interest Rate	6.125%
Debt Instrument Call Feature Ultra Petroleum Corp Senior Notes Due 2024	On and after October 1, 2019, the Company may redeem all or, from time to time, a part of the 2024 Notes at the following prices expressed as a percentage of principal amount of the 2024 Notes: (2019 – 103.063%; 2020 – 102.042%; 2021 – 101.021%; and 2022 and thereafter – 100.000%).
Senior Notes Ultra Petroleum Corp Due 2018	$ 450,000,000
Senior Notes Ultra Petroleum Corp Due 2018 Interest Rate	5.75%
Debt Instrument Call Feature	On and after December 15, 2015, the Company may redeem all or, from time to time, a part of the 2018 Notes at the following prices expressed as a percentage of principal amount of the 2018 Notes: (2015 – 102.875%; 2016 – 101.438%; and 2017 and thereafter – 100.000%).

Percentage requirement from consenting banks for commitment extensions under the revolving credit facility.

No definition available.

Name:	upl_CreditFacilityLenderConsentRequirement
Namespace Prefix:	upl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Description of a feature that permits the issuer of the debt to repay or convert it before the stated maturity date (early retirement date). The description may include such items as the call price, the period that the issuer can call the debt, including the earliest call date, and other significant terms of the call feature, which may include the debt holders' ability to convert the debt to equity if the call option is exercised and contingent events that trigger the issuer's ability to call the debt.

+ References

No definition available.

+ Details

Name:	upl_DebtInstrumentCallFeatureUltraPetroleumCorpSeniorNotesDue2024
Namespace Prefix:	upl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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.

+ References

No definition available.

+ Details

Name:	upl_DebtInstrumentInterestRateTermsLibor
Namespace Prefix:	upl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- 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.

+ References

No definition available.

+ Details

Name:	upl_DebtInstrumentInterestRateTermsPrime
Namespace Prefix:	upl_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount available to be issued as letters of credit under the Company's bank credit facility.

+ References

No definition available.

+ Details

Name:	upl_LettersOfCreditAvailability
Namespace Prefix:	upl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum aggregate commitment available under the current revolving credit facility.

+ References

No definition available.

+ 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.

+ References

No definition available.

+ Details

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

- Details

Name:	upl_SeniorCreditFacilityDetailsAbstract
Namespace Prefix:	upl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding principal amount of Senior Notes due 2018 at the parent company level

+ References

No definition available.

+ Details

Name:	upl_SeniorNotesUltraPetroleumCorpDue2018
Namespace Prefix:	upl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fixed interest rate related to the outstanding principal amount of Senior Notes due 2018 at the parent company level.

+ References

No definition available.

+ Details

Name:	upl_SeniorNotesUltraPetroleumCorpDue2018InterestRate
Namespace Prefix:	upl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding principal amount of Senior Notes due 2024 at the parent company level.

+ References

No definition available.

+ Details

Name:	upl_SeniorNotesUltraPetroleumCorpDue2024
Namespace Prefix:	upl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fixed interest rate related to the outstanding principal amount of Senior Notes due 2024 at the parent company level.

+ References

No definition available.

+ Details

Name:	upl_SeniorNotesUltraPetroleumCorpDue2024InterestRate
Namespace Prefix:	upl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Outstanding principal amount of Senior Notes at the subsidiary level.

+ References

No definition available.

+ Details

Name:	upl_SeniorNotesUltraResourcesInc
Namespace Prefix:	upl_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	upl_UltraPetroleumCorpSeniorNotesAbstract
Namespace Prefix:	upl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	upl_UltraResourcesIncSeniorNotesAbstract
Namespace Prefix:	upl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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 210.5-02.22(a)(5))

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

+ Details

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

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(b))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Subparagraph b

-Article 5

+ Details

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

- Definition

Amount of commitment fees for the unused borrowing capacity under the long-term financing arrangement that is available to the entity.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnusedBorrowingCapacityFee
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Including the current and noncurrent portions, the carrying value as of the balance sheet date of notes payable to banks, excluding mortgage notes, initially due beyond one year or beyond the operating cycle if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

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