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Debt - Additional Information (Detail) (USD $)
Share data in Millions, unless otherwise specified
 3 Months Ended 12 Months Ended 1 Months Ended 0 Months Ended 1 Months Ended 0 Months Ended 1 Months Ended 0 Months Ended 1 Months Ended
Dec. 31, 2014
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jan. 31, 2014
Nov. 30, 2013
May 31, 2013
Jan. 31, 2015
Jan. 31, 2015
Mar. 27, 2013
Sep. 30, 2014
Sep. 30, 2014
Oct. 10, 2014
Mar. 31, 2014
Jan. 17, 2014
Debt Instrument [Line Items]                                
Debt purchased and retired         $ 212,000,000us-gaap_ExtinguishmentOfDebtAmount                      
Long-term Debt, Gross 248,000,000us-gaap_DebtInstrumentCarryingAmount   248,000,000us-gaap_DebtInstrumentCarryingAmount                          
Debt extinguishment charge 53,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt 21,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt 74,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt   309,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt                      
Aggregate principal amount of convertible senior notes exchanged       240,000,000us-gaap_DebtConversionOriginalDebtAmount1                        
Senior Notes 6% Due 2020                                
Debt Instrument [Line Items]                                
Debt instrument stated interest rate 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SeniorNotesSixPercentDueTwentyTwentyMember		   6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SeniorNotesSixPercentDueTwentyTwentyMember		                          
6.375% Senior Notes due 2018                                
Debt Instrument [Line Items]                                
Debt instrument stated interest rate 6.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPointThreeSevenFivePercentSeniorNotesDueTwentyEighteenMember		   6.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPointThreeSevenFivePercentSeniorNotesDueTwentyEighteenMember		                          
4.5% Convertible Notes Due 2015                                
Debt Instrument [Line Items]                                
Debt instrument stated interest rate 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember		   4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember		                          
6% Convertible Junior Subordinated Debentures due 2030                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2030                          
Debt instrument stated interest rate 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentageConvertibleJuniorSubordinatedDebenturesDueTwentyThirtyMember		   6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentageConvertibleJuniorSubordinatedDebenturesDueTwentyThirtyMember		                          
6% Convertible Senior Notes                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2029 2029                        
Debt instrument stated interest rate 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		   6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		                        
Common stock issued in exchange for convertible notes     12us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		 28us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		                        
Debt instrument converted amount     104,000,000us-gaap_DebtConversionConvertedInstrumentAmount1
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		                          
Aggregate principal amount of convertible senior notes exchanged     104,000,000us-gaap_DebtConversionOriginalDebtAmount1
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		 240,000,000us-gaap_DebtConversionOriginalDebtAmount1
/ us-gaap_DebtInstrumentAxis
= ual_SixPercentConvertibleSeniorNotesMember		                        
Unsecured Debt                                
Debt Instrument [Line Items]                                
Debt instrument maturity year           2021                    
Debt instrument stated interest rate           4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                    
Common stock issued in exchange for convertible notes           5us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                    
Debt extinguishment charge     74,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Debt instrument converted amount           156,000,000us-gaap_DebtConversionConvertedInstrumentAmount1
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                    
Unsecured Debt | Senior Notes 6% Due 2020                                
Debt Instrument [Line Items]                                
Debt instrument maturity date             Dec. 01, 2020                  
Debt instrument stated interest rate             6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SeniorNotesSixPercentDueTwentyTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                  
Aggregate principal amount             300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ual_SeniorNotesSixPercentDueTwentyTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                  
Debt instrument redemption percentage             101.00%us-gaap_DebtInstrumentRedemptionPricePercentage
/ us-gaap_DebtInstrumentAxis
= ual_SeniorNotesSixPercentDueTwentyTwentyMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                  
Unsecured Debt | 6.375% Senior Notes due 2018                                
Debt Instrument [Line Items]                                
Debt instrument maturity date               Jun. 01, 2018                
Debt instrument stated interest rate               6.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPointThreeSevenFivePercentSeniorNotesDueTwentyEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                
Aggregate principal amount               300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_DebtInstrumentAxis
= ual_SixPointThreeSevenFivePercentSeniorNotesDueTwentyEighteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                
Unsecured Debt | 4.5% Convertible Notes Due 2015                                
Debt Instrument [Line Items]                                
Debt purchased and retired     28,000,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Debt instrument maturity year     2015                          
Long-term Debt, Gross 202,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		   202,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Debt instrument stated interest rate 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		   4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Debt instrument conversion rate     18.93us-gaap_DebtInstrumentConvertibleConversionRatio1
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Adjustment to additional paid in capital upon debt redemption     34,000,000us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                          
Unsecured Debt | 4.5% Convertible Notes Due 2015 | Subsequent Event                                
Debt Instrument [Line Items]                                
Long-term Debt, Gross                 202,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		 202,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		            
Debt instrument stated interest rate                 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		            
Common stock issued in exchange for convertible notes                   11us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		            
Debt instrument converted amount                 202,000,000us-gaap_DebtConversionConvertedInstrumentAmount1
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentConvertibleNotesDueTwoThousandFifteenMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember		              
Unsecured Debt | 8% Notes due 2024                                
Debt Instrument [Line Items]                                
Aggregate principal amount of debt redeemed                               400,000,000us-gaap_DebtInstrumentRepurchaseAmount
/ us-gaap_DebtInstrumentAxis
= ual_EightPercentNotesDueTwentyTwentyFourMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember
Unsecured Debt | 4.5% Senior Limited-Subordination Convertible Notes Due 2021                                
Debt Instrument [Line Items]                                
Debt instrument maturity year   2021                            
Debt instrument stated interest rate   4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentageSeniorLimitedSubordinationConvertibleNotesDueTwentyTwentyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                         4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentageSeniorLimitedSubordinationConvertibleNotesDueTwentyTwentyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		  
Debt instrument conversion rate   30.6419us-gaap_DebtInstrumentConvertibleConversionRatio1
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentageSeniorLimitedSubordinationConvertibleNotesDueTwentyTwentyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                            
Debt instrument converted amount   156,000,000us-gaap_DebtConversionConvertedInstrumentAmount1
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentageSeniorLimitedSubordinationConvertibleNotesDueTwentyTwentyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                            
Debt instrument converted shares issued   5us-gaap_DebtConversionConvertedInstrumentSharesIssued1
/ us-gaap_DebtInstrumentAxis
= ual_FourPointFivePercentageSeniorLimitedSubordinationConvertibleNotesDueTwentyTwentyOneMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                            
Term Loan Facility | Secured Debt                                
Debt Instrument [Line Items]                                
Credit Agreement                     900,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= ual_TermLoanFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		          
Debt instrument maturity date                     Apr. 01, 2019          
Amount utilized to repay term loan                     900,000,000us-gaap_ProceedsFromLongTermLinesOfCredit
/ us-gaap_CreditFacilityAxis
= ual_TermLoanFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		          
Revolving Credit Facility | Secured Debt                                
Debt Instrument [Line Items]                                
Credit Agreement                     1,000,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		 1,315,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		 1,315,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		      
Debt instrument maturity date                       Jan. 02, 2019        
Revolving credit facility available for drawing date                     Apr. 01, 2018          
Revolving Credit Facility | Secured Debt | Before amendment                                
Debt Instrument [Line Items]                                
Credit Agreement                       1,000,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ ual_CreditFacilityAmendmentAxis
= ual_BeforeAmendmentMember
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		 1,000,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ ual_CreditFacilityAmendmentAxis
= ual_BeforeAmendmentMember
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		      
Revolving Credit Facility | Secured Debt | After amendment                                
Debt Instrument [Line Items]                                
Credit Agreement                       1,350,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ ual_CreditFacilityAmendmentAxis
= ual_AfterAmendmentMember
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		 1,350,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ ual_CreditFacilityAmendmentAxis
= ual_AfterAmendmentMember
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		      
Amended Credit Facility | Secured Debt                                
Debt Instrument [Line Items]                                
Cash utilized to repay term loan                     300,000,000us-gaap_RepaymentsOfDebt
/ us-gaap_CreditFacilityAxis
= ual_AmendedCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		          
Debt purchased and retired                     1,200,000,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_CreditFacilityAxis
= ual_AmendedCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		          
Debt instrument maturity year                     2014          
Performance Bonds | Secured Debt                                
Debt Instrument [Line Items]                                
Credit facility expiration year     2019                          
United Airlines, Inc.                                
Debt Instrument [Line Items]                                
Long-term Debt, Gross 11,533,000,000us-gaap_DebtInstrumentCarryingAmount
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		   11,533,000,000us-gaap_DebtInstrumentCarryingAmount
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		 11,604,000,000us-gaap_DebtInstrumentCarryingAmount
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		                        
Difference in long term debt noncurrent 1,000,000ual_DifferenceInLongTermDebtNoncurrent
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		   1,000,000ual_DifferenceInLongTermDebtNoncurrent
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		 47,000,000ual_DifferenceInLongTermDebtNoncurrent
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		                        
United Airlines, Inc. | Convertible Debt Derivative Asset                                
Debt Instrument [Line Items]                                
Convertible debt derivative asset 712,000,000us-gaap_DerivativeAssets
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtSupplementalDerivativeAssetMember		   712,000,000us-gaap_DerivativeAssets
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtSupplementalDerivativeAssetMember		 480,000,000us-gaap_DerivativeAssets
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtSupplementalDerivativeAssetMember		                        
United Airlines, Inc. | Convertible Debt Option Liability                                
Debt Instrument [Line Items]                                
Convertible debt option liability 511,000,000us-gaap_DerivativeLiabilities
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtConversionOptionLiabilityMember		   511,000,000us-gaap_DerivativeLiabilities
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtConversionOptionLiabilityMember		 270,000,000us-gaap_DerivativeLiabilities
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_ScheduleOfFairValueOfSeparateAccountsByMajorCategoryOfInvestmentAxis
= ual_ConvertibleDebtConversionOptionLiabilityMember		                        
United Airlines, Inc. | Pass-through certificates                                
Debt Instrument [Line Items]                                
Long term debt 7,200,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ual_PassThroughCertificatesMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		   7,200,000,000us-gaap_LongTermDebt
/ us-gaap_DebtInstrumentAxis
= ual_PassThroughCertificatesMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		                          
United Airlines, Inc. | Secured Debt | 6.75% senior secured notes due 2015                                
Debt Instrument [Line Items]                                
Debt purchased and retired                         800,000,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
= ual_SixPointSevenFivePercentSeniorSecuredNotesDueTwoThousandFifteenMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		      
Debt instrument maturity year     2015 2015                        
Long-term Debt, Gross       800,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
= ual_SixPointSevenFivePercentSeniorSecuredNotesDueTwoThousandFifteenMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		                        
Debt instrument stated interest rate 6.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPointSevenFivePercentSeniorSecuredNotesDueTwoThousandFifteenMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		   6.75%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
= ual_SixPointSevenFivePercentSeniorSecuredNotesDueTwoThousandFifteenMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
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United Airlines, Inc. | Unsecured Debt | Senior Notes 6% Due 2020                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2020 [1] 2020 [1]                        
Long-term Debt, Gross 300,000,000us-gaap_DebtInstrumentCarryingAmount
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Debt instrument stated interest rate 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
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United Airlines, Inc. | Unsecured Debt | 6.375% Senior Notes due 2018                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2018 [1] 2018 [1]                        
Long-term Debt, Gross 300,000,000us-gaap_DebtInstrumentCarryingAmount
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Debt instrument stated interest rate 6.375%us-gaap_DebtInstrumentInterestRateStatedPercentage
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United Airlines, Inc. | Unsecured Debt | 4.5% Convertible Notes Due 2015                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2015 2015                        
Long-term Debt, Gross 202,000,000us-gaap_DebtInstrumentCarryingAmount
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Debt instrument stated interest rate 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
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/ us-gaap_DebtInstrumentAxis
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Adjustment to additional paid in capital upon debt redemption     62,000,000us-gaap_AdjustmentsToAdditionalPaidInCapitalEquityComponentOfConvertibleDebt
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Debt instrument convertible effective interest rate 4.50%us-gaap_DebtInstrumentInterestRateEffectivePercentage
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United Airlines, Inc. | Unsecured Debt | 8% Notes due 2024                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2024 [1] 2024 [1]                        
Long-term Debt, Gross       400,000,000us-gaap_DebtInstrumentCarryingAmount
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Debt instrument stated interest rate 8.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
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/ us-gaap_LongtermDebtTypeAxis
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United Airlines, Inc. | Unsecured Debt | 6% Convertible Junior Subordinated Debentures due 2030                                
Debt Instrument [Line Items]                                
Debt purchased and retired                           248,000,000us-gaap_ExtinguishmentOfDebtAmount
/ us-gaap_DebtInstrumentAxis
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Debt instrument maturity year     2030 2030                        
Long-term Debt, Gross       248,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_DebtInstrumentAxis
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Debt instrument stated interest rate 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		   6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_LongtermDebtTypeAxis
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/ us-gaap_DebtInstrumentAxis
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/ dei_LegalEntityAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		                   6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
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/ dei_LegalEntityAxis
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/ us-gaap_LongtermDebtTypeAxis
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Debt extinguishment charge 64,000,000us-gaap_GainsLossesOnExtinguishmentOfDebt
/ us-gaap_DebtInstrumentAxis
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United Airlines, Inc. | Unsecured Debt | 4.5% Senior Limited-Subordination Convertible Notes Due 2021                                
Debt Instrument [Line Items]                                
Debt instrument maturity year     2021 [1] 2021 [1]                        
Long-term Debt, Gross       156,000,000us-gaap_DebtInstrumentCarryingAmount
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Debt instrument stated interest rate 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
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/ us-gaap_DebtInstrumentAxis
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/ dei_LegalEntityAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_UnsecuredDebtMember		 [1] 4.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_DebtInstrumentAxis
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
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United Airlines, Inc. | Term Loan Facility                                
Debt Instrument [Line Items]                                
Credit Agreement                     900,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		 500,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
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/ dei_LegalEntityAxis
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		      
Credit agreement, outstanding 884,000,000us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
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/ dei_LegalEntityAxis
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/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		      
Debt instrument maturity date                       2021-09        
United Airlines, Inc. | Term Loan Facility | LIBOR                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                       3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
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/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		        
United Airlines, Inc. | Term Loan Facility | Interest Rate Floor                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                       0.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
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/ us-gaap_VariableRateAxis
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United Airlines, Inc. | Revolving Credit Facility                                
Debt Instrument [Line Items]                                
Commitment fee percentage                             0.75%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
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/ dei_LegalEntityAxis
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United Airlines, Inc. | Revolving Credit Facility | LIBOR                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                             3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		  
United Airlines, Inc. | Revolving Credit Facility | Certain Market Interest Rates                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                             2.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
= us-gaap_RevolvingCreditFacilityMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_VariableRateAxis
= ual_CertainMarketInterestRatesMember		  
United Airlines, Inc. | Revolving Credit Facility | Secured Debt                                
Debt Instrument [Line Items]                                
Available under revolving credit facility 1,350,000,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		                          
United Airlines, Inc. | Term Loan | Secured Debt                                
Debt Instrument [Line Items]                                
Debt instrument maturity date                             Apr. 01, 2019  
Long-term Debt, Gross   893,000,000us-gaap_DebtInstrumentCarryingAmount
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= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		                         893,000,000us-gaap_DebtInstrumentCarryingAmount
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/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
Quarterly principal repayment amount                             0.25%ual_DebtInstrumentQuarterlyPrincipalRepaymentPercentage
/ us-gaap_CreditFacilityAxis
= ual_TermLoanMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember		  
Commencement date of installment payment                             Jun. 30, 2013  
United Airlines, Inc. | Term Loan | Secured Debt | LIBOR | Before amendment                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                             3.00%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ ual_CreditFacilityAmendmentAxis
= ual_BeforeAmendmentMember
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= ual_TermLoanMember
/ dei_LegalEntityAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		  
United Airlines, Inc. | Term Loan | Secured Debt | LIBOR | After amendment                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                             2.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ ual_CreditFacilityAmendmentAxis
= ual_AfterAmendmentMember
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_VariableRateAxis
= us-gaap_LondonInterbankOfferedRateLIBORMember		  
United Airlines, Inc. | Term Loan | Secured Debt | Interest Rate Floor                                
Debt Instrument [Line Items]                                
Debt instrument, basis spread on variable rate                             0.75%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
/ us-gaap_CreditFacilityAxis
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/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SecuredDebtMember
/ us-gaap_VariableRateAxis
= us-gaap_InterestRateFloorMember		  
United Airlines, Inc. | Letters of credit | Cash Collateralized Letters of Credit                                
Debt Instrument [Line Items]                                
Credit agreement, outstanding 74,000,000us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		   74,000,000us-gaap_LineOfCredit
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= us-gaap_LetterOfCreditMember
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedDebtObligationsMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		                          
United Airlines, Inc. | Letter of Credit and Performance Bonds                                
Debt Instrument [Line Items]                                
Credit agreement, outstanding $ 410,000,000us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= ual_LetterOfCreditAndPerformanceBondsMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		   $ 410,000,000us-gaap_LineOfCredit
/ us-gaap_CreditFacilityAxis
= ual_LetterOfCreditAndPerformanceBondsMember
/ dei_LegalEntityAxis
= ual_UnitedAirLinesIncMember		                          
[1] UAL is the issuer of this debt. United is a guarantor.