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Details of Pass Through Trusts (Detail) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Debt Instrument [Line Items] |  |
Total proceeds received from issuance of debt during 2018 and recorded as debt | $ 696 | $ 755
United Airlines, Inc. |  |
Debt Instrument [Line Items] |  |
Principal | 935 |
Total proceeds received from issuance of debt during 2018 and recorded as debt | 696 | $ 755
United Airlines, Inc. | February Twenty Eighteen [Member] |  |
Debt Instrument [Line Items] |  |
Total proceeds received from issuance of debt during 2018 and recorded as debt | 657 |
Remaining proceeds from issuance of debt to be received in future periods | 278 |
United Airlines, Inc. | Class AA Pass Through Certificates | February Twenty Eighteen [Member] |  |
Debt Instrument [Line Items] |  |
Principal | $ 677 |
Final expected distribution date | 2030-03 |
Stated interest rate | 3.50% |
Total proceeds received from issuance of debt during 2018 and recorded as debt | $ 476 |
Remaining proceeds from issuance of debt to be received in future periods | 201 |
United Airlines, Inc. | Class A Pass Through Certificates | February Twenty Eighteen [Member] |  |
Debt Instrument [Line Items] |  |
Principal | $ 258 |
Final expected distribution date | 2030-03 |
Stated interest rate | 3.70% |
Total proceeds received from issuance of debt during 2018 and recorded as debt | $ 181 |
Remaining proceeds from issuance of debt to be received in future periods | $ 77 |

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