Derivative Financial Instruments - Summary of Open Commodity Derivative Contracts (Details) $ in Thousands, bbl in Millions, MMBTU in Millions	3 Months Ended
Mar. 31, 2020 USD ($) MMBTU $ / bbl $ / MMBTU bbl	Dec. 31, 2019 USD ($)
Derivative [Line Items]
Fair Value Asset	$ 44,261	$ 32,100
Fair Value (Liability)	$ (4,866)	$ (20,692)
Commodity Derivative Contract Fixed Price Swaps \| Crude Oil
Derivative [Line Items]
Type	Crude oil fixed price swaps
Commodity Derivative Contract Fixed Price Swaps One \| Crude Oil
Derivative [Line Items]
Year	2020 (April through September)
Index	NYMEX-WTI
Total Volumes \| bbl	0.2
Weighted Average Price per Unit \| $ / bbl	59.79
Fair Value Asset	$ 7,960
Commodity Derivative Contract Collars \| Natural Gas
Derivative [Line Items]
Type	Natural gas collars
Commodity Derivative Contract Collars One \| Natural Gas
Derivative [Line Items]
Year	2020 (April through December)
Index	NYMEX
Total Volumes \| MMBTU	57.4
Weighted Average Floor Price \| $ / MMBTU	2.39
Weighted Average Ceiling Price \| $ / MMBTU	2.87
Fair Value Asset	$ 26,255
Commodity Derivative Contract Collars Two \| Natural Gas
Derivative [Line Items]
Year	2021
Index	NYMEX
Total Volumes \| MMBTU	7.2
Weighted Average Floor Price \| $ / MMBTU	2.46
Weighted Average Ceiling Price \| $ / MMBTU	3.05
Fair Value (Liability)	$ (180)
Commodity Derivative Contract Deferred Premium Put Options \| Natural Gas
Derivative [Line Items]
Type	Natural gas deferred premium put options
Commodity Derivative Contract Put Options One \| Natural Gas
Derivative [Line Items]
Year	2020 (April through December)
Index	NYMEX
Total Volumes \| MMBTU	13.4
Weighted Average Floor Price \| $ / MMBTU	2.42
Fair Value Asset	$ 5,360

Derivative contract maturity period.

No definition available.

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

- Definition

Derivative maturity period.

+ References

No definition available.

+ Details

Name:	upl_DerivativeMaturityPeriod
Namespace Prefix:	upl_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

+ Details

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

- Definition

The average cap rate on a group of price risk derivatives such as caps or collars. A payment or receipt is triggered if the market rate exceeds the cap rate on the contract.

+ References

No definition available.

+ Details

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

- Definition

The average floor rate on a group of price risk derivatives such as floors or collars. A payment or receipt is triggered if the market rate falls below the floor rate on the contract.

+ References

No definition available.

+ Details

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

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset, expected to be settled within one year or normal operating cycle, if longer. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

+ Details

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

Nominal energy measure used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountEnergyMeasure
Namespace Prefix:	us-gaap_
Data Type:	num:energyItemType
Balance Type:	na
Period Type:	duration

- Definition

Nominal volume used to calculate payments on a derivative instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountVolume
Namespace Prefix:	us-gaap_
Data Type:	num:volumeItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicates whether the entity pays a variable or fixed price on a price risk swap.

+ References

No definition available.

+ Details

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

- Definition

Average fixed price related to the group of price risk swap derivatives.

+ References

No definition available.

+ Details

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

- 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

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractFixedPriceSwapsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_EnergyAxis=srt_CrudeOilMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractFixedPriceSwapsOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractCollarsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ReserveQuantitiesByTypeOfReserveAxis=srt_NaturalGasReservesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractCollarsOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractCollarsTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractDeferredPremiumPutOptionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=upl_CommodityDerivativeContractPutOptionsOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: