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Advanced Purchase of Miles - Additional Information (Detail) (United Airlines, Inc., Co-Brand Agreement, Maximum, Advanced Purchase of Miles, USD $)
In Millions, unless otherwise specified
Dec. 31, 2014
United Airlines, Inc. | Co-Brand Agreement | Maximum | Advanced Purchase of Miles
  
Airline Products and Services [Line Items]  
Repurchase of pre-purchased miles from Chase in 2015 $ 224us-gaap_RecordedUnconditionalPurchaseObligationDueWithinOneYear
/ ual_ContractTypeAxis
= ual_CoBrandAgreementMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis
= ual_AdvancePurchaseOfMileageCreditsMember
Repurchase of pre-purchased miles from Chase in 2016 $ 249us-gaap_RecordedUnconditionalPurchaseObligationDueInSecondYear
/ ual_ContractTypeAxis
= ual_CoBrandAgreementMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
/ us-gaap_RecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis
= ual_AdvancePurchaseOfMileageCreditsMember