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Commitments and Contingencies - Additional Information (Detail) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) Employee Option Aircraft | Feb. 28, 2018 USD ($)
Commitments and Contingencies [Line Items] |  |
Aggregate balance | $ 11,500,000,000 |
Number of call options to purchase regional jet aircraft | Option | 257 |
Subsequent Event | EETC |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument principal amount |  | $ 935,000,000
Boeing 737 MAX Aircraft [Member] |  |
Commitments and Contingencies [Line Items] |  |
Number of aircrafts expects to take delivery | Aircraft | 10 |
Boeing 787 Aircraft [Member] |  |
Commitments and Contingencies [Line Items] |  |
Number of aircrafts expects to take delivery | Aircraft | 7 |
Boeing 777-300ER Aircraft [Member] |  |
Commitments and Contingencies [Line Items] |  |
Number of aircrafts expects to take delivery | Aircraft | 4 |
Aircraft Mortgage Debt |  |
Commitments and Contingencies [Line Items] |  |
Guarantor obligations, maximum exposure | $ 157,000,000 |
Tax-exempt special facilities revenue bonds |  |
Commitments and Contingencies [Line Items] |  |
Guarantor obligations, maximum exposure | 1,800,000,000 |
Operating leases obligations | 1,400,000,000 |
Capital leases obligations | 441,000,000 |
Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness |  |
Commitments and Contingencies [Line Items] |  |
Guarantor obligations, maximum exposure | 244,000,000 |
Contingent liabilities based on participation | 1,500,000,000 |
Floating Rate Debt |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument principal amount | 3,400,000,000 |
Fixed Rate Debt |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument principal amount | 60,000,000 |
Loans And Leases From Non U S Entities |  |
Commitments and Contingencies [Line Items] |  |
Aggregate balance | $ 3,300,000,000 |
Minimum | Tax-exempt special facilities revenue bonds |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument maturity year | 2019 |
Minimum | Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument maturity year | 2022 |
Maximum |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument, remaining terms (years) | 11 years |
Maximum | Tax-exempt special facilities revenue bonds |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument maturity year | 2038 |
Maximum | Tax-exempt special facilities revenue bonds | Indirect Guarantee of Indebtedness |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument maturity year | 2049 |
Maximum | Loans And Leases From Non U S Entities |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument, remaining terms (years) | 11 years |
United Airlines, Inc. |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument principal amount | $ 497,000,000 |
Number of employees | Employee | 89,800 |
Percentage of employees represented by various U.S. labor organizations | 80.00% |
United Airlines, Inc. | EETC |  |
Commitments and Contingencies [Line Items] |  |
Debt instrument principal amount | $ 3,402,000,000 |

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