Name:	ual_DefinedBenefitPlanNetPeriodicBenefitCostCreditGainLossDueToSettlementRestructuringAndSpecialAndContractualTerminationBenefits
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due To Special And Contractual Termination Benefits

No definition available.

Name:	ual_DefinedBenefitPlanNetPeriodicBenefitCostCreditGainLossDueToSpecialAndContractualTerminationBenefits
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Defined Benefit Plan, Plan Assets, Employer Discretionary Contribution Amount

No definition available.

Name:	ual_DefinedBenefitPlanPlanAssetsEmployerDiscretionaryContributionAmount
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

The time period over which the stock closing prices are averaged to arrive at a per-share valuation for equity based awards such as Restricted Stock Units, Performance Share and other equity based awards.

No definition available.

Name:	ual_DeterminationPeriodAverageClosingPrice
Namespace Prefix:	ual_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Restructuring Programs, One-Time Contribution Per Employee

No definition available.

Name:	ual_RestructuringProgramsOneTimeContributionPerEmployee
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- References

No definition available.

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

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Description of terms of award under share-based payment arrangement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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

Percentage of vesting of award under share-based payment arrangement.

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_EmployeeSeveranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RestructuringPlanAxis=ual_VoluntarySeparationLeaveVSLProgramsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ual_EmployeeClassificationAxis=ual_PartTimeEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	ual_EmployeeClassificationAxis=ual_FullTimeEmployeesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_AwardTypeAxis=ual_TimeVestedRestrictedStockUnitsRSUsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: