Derivative Financial Instruments - Summary of Pre-tax Realized and Unrealized Gain (Loss) Recognized Related to Derivative Instruments (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Unrealized gain on commodity derivatives	$ 27,945	$ 14,292
Total gain (loss) on commodity derivatives	44,294	(64,339)
Commodity Derivative Contract
Derivative [Line Items]
Unrealized gain on commodity derivatives	27,945	14,292
Total gain (loss) on commodity derivatives	44,294	(64,339)
Commodity Derivative Contract \| Natural Gas
Derivative [Line Items]
Realized gain (loss) on commodity derivatives	11,452	(81,203)
Commodity Derivative Contract \| Oil Reserves
Derivative [Line Items]
Realized gain (loss) on commodity derivatives	$ 4,897	$ 2,572

The realized and unrealized gain (loss) on commodity derivatives relating to actual amounts received or paid under the respective contracts and the realized and unrealized gain or loss on commodity derivative contracts representing the change in the fair market value of derivative instruments that have not actually settled.

No definition available.

+ Details

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

- Definition

Actual amounts received or paid related to natural gas derivative instruments, including options, swaps, futures, and forward contracts, which were included in earnings in the period.

+ References

No definition available.

+ Details

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

- 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

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivatives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
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:	srt_ReserveQuantitiesByTypeOfReserveAxis=srt_OilReservesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: