Hedging Activities - Additional Information (Detail) $ in Millions	9 Months Ended
Sep. 30, 2015 USD ($) gal	Dec. 31, 2014 USD ($)
Derivatives And Hedging Activities [Line Items]
Fuel hedges expiration date	2016-12
Fuel hedge collateral deposits	$ 156	$ 577
Fair value of derivative asset	$ 17	6
Cash Flow Hedging
Derivatives And Hedging Activities [Line Items]
Percentage of projection of European euro for hedging financial instruments for remainder of 2015	36.00%
Percentage of projection of European euro for hedging financial instruments for 2016	21.00%
Foreign Currency Derivatives Asset, Net
Derivatives And Hedging Activities [Line Items]
Fair value of derivative asset	$ 2
2015 Projected
Derivatives And Hedging Activities [Line Items]
Percentage of projection for hedging financial instruments	23.00%
Volume of fuel hedging \| gal	221,000,000
2016 Projected
Derivatives And Hedging Activities [Line Items]
Percentage of projection for hedging financial instruments	17.00%
Volume of fuel hedging \| gal	652,000,000
Fuel Derivative Instruments
Derivatives And Hedging Activities [Line Items]
Fuel hedge collateral deposits	$ 156	$ 577

Aggregate notional amount of derivative expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

Name:	invest_DerivativeNonmonetaryNotionalAmount
Namespace Prefix:	invest_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash Collateral Posted For Derivatives Liability

+ References

No definition available.

+ Details

Name:	ual_CashCollateralPostedForDerivativesLiability
Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Derivative Instrument Expiry Date

+ References

No definition available.

+ Details

Name:	ual_DerivativeInstrumentExpiryDate
Namespace Prefix:	ual_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- Definition

Derivatives And Hedging Activities [Line Items]

+ References

No definition available.

+ Details

Name:	ual_DerivativesAndHedgingActivitiesLineItems
Namespace Prefix:	ual_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The percentage of projected European euro denominated net cash inflows that are hedged with foreign currency derivatives

+ References

No definition available.

+ Details

Name:	ual_HedgingContractAsPercentageOfProjectedEuropeanEuroNetCashInflow
Namespace Prefix:	ual_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Hedging contract as percentage of projected European euro net cash inflow in year two.

+ References

No definition available.

+ Details

Name:	ual_HedgingContractAsPercentageOfProjectedEuropeanEuroNetCashInflowInYearTwo
Namespace Prefix:	ual_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fair value, before 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. Includes assets elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=51825145&loc=SL20226000-175313

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 20

-Section 50

-Paragraph 4D

-Subparagraph (c)(2)

-URI http://asc.fasb.org/extlink&oid=51814546&loc=SL51823488-111719

+ Details

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

- Definition

The percentage of expected requirements covered by the aggregate notional amount of derivative contracts expressed in nonmonetary units. For example, the number of barrels specified in a fuel oil forward purchase contract as a percentage of expected need.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeNonmonetaryNotionalAmountPercentOfRequiredNeedCoverage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis=us-gaap_CashFlowHedgingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	ual_YearAxis=ual_YearOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ual_YearAxis=ual_YearTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=ual_FuelDerivativesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: