XML 54 R36.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Financial Instruments and Fair Value Measurements - Additional Information (Detail) | 9 Months Ended
--- | ---
Sep. 30, 2017
EETC |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 2019
Asset-backed Securities | Minimum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 1 year
Asset-backed Securities | Maximum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 17 years
Corporate Debt | Minimum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 1 year
Corporate Debt | Maximum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 3 years
CDARS | Maximum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 1 year
U.S. Government and Other Securities | Minimum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 1 year
U.S. Government and Other Securities | Maximum |
Fair Value [Line Items] |
Available-for-sale securities remaining maturities | 2 years

X
- Definition Available for Sale Investment Maturity Term + References No definition available. + Details
Name: | ual_AvailableForSaleInvestmentMaturityTerm
Namespace Prefix: | ual_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Available for Sale Investment Maturity Year + References No definition available. + Details
Name: | ual_AvailableForSaleInvestmentMaturityYear
Namespace Prefix: | ual_
Data Type: | xbrli:gYearItemType
Balance Type: | na
Period Type: | duration

X
- Definition Fair Value [Line Items] + References No definition available. + Details
Name: | ual_FairValueLineItems
Namespace Prefix: | ual_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=us-gaap_EnhancedEquipmentTrustCertificateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=us-gaap_CertificatesOfDepositMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByAssetClassAxis=ual_UsGovernmentAgenciesDebtSecuritiesAndOtherFixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |