Borrowing base.

No definition available.

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

- Definition

Line of credit facility covenant, maximum required consolidated net leverage ratio on rolling period one.

+ References

No definition available.

+ Details

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

- Definition

Line of credit facility covenant, maximum required consolidated net leverage ratio on rolling period three.

+ References

No definition available.

+ Details

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

- Definition

Line of credit facility covenant, maximum required consolidated net leverage ratio on rolling period two.

+ References

No definition available.

+ Details

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

- Definition

Line of credit facility covenant, minimum required consolidated net leverage ratio, incremental interest rate.

+ References

No definition available.

+ Details

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

- Definition

Line of credit facility covenant, rolling period one, minimum required hedging percentage.

+ References

No definition available.

+ Details

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

- Definition

Line of credit facility covenant, rolling period two, minimum required hedging percentage.

+ References

No definition available.

+ Details

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

- Definition

The number of positions eliminated during the period as a result of restructuring activities.

+ References

No definition available.

+ Details

Name:	us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=upl_HoustonOfficeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=upl_CreditAgreementSecondAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=upl_BankOfMontrealMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=us-gaap_SubsidiaryIssuerMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
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Subsequent Events - Additional Information (Details) - Subsequent Event $ in Billions	May 10, 2018 Employee	Apr. 20, 2018	Apr. 19, 2018 USD ($)
Houston Office
Subsequent Event [Line Items]
Number of expected reduction in employees \| Employee	14
Second Amendment \| Bank Of Montreal
Subsequent Event [Line Items]
Borrowing Base			$ 1.4
Ultra Resources, Inc. \| Second Amendment \| Bank Of Montreal
Subsequent Event [Line Items]
Borrowing Base			$ 1.4
Ultra Resources, Inc. \| Second Amendment \| Bank Of Montreal \| Revolving Credit Facility
Subsequent Event [Line Items]
Minimum required consolidated net leverage ratio, as percentage beginning on last day of June 30, 2018 and ending on last day of June 30, 2019		450.00%
Maximum required consolidated net leverage ratio, as percentage beginning on last day of September 30, 2019 and ending on last day of December 31, 2019		425.00%
Maximum required consolidated net leverage ratio, as percentage beginning on last day of March 31, 2020		400.00%
Net leverage ratio beginning on June 30, 2018 and ending on September 29, 2019, minimum required hedging percentage		65.00%
Net leverage ratio beginning on September 30, 2019 and ending on March 30, 2020, minimum required hedging percentage		50.00%
Interest rate on minimum required consolidated net leverage ratio exceeds 4.00 to 1.00		0.25%