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Details of Pass Through Trusts (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Debt Instrument [Line Items] |  |  |
Proceeds received from issuance of debt | $ 2,765 | $ 808 | $ 1,073
United Airlines, Inc. |  |  |
Debt Instrument [Line Items] |  |  |
Principal | 497 |  |
Proceeds received from issuance of debt | 2,765 | $ 808 | $ 1,073
United Airlines, Inc. | Class B Pass Through Certificates | November 2017 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 258 |  |
Final expected distribution date | 2026-01 |  |
Stated interest rate | 3.65% |  |
Total debt recorded | $ 258 |  |
Proceeds received from issuance of debt | 258 |  |
United Airlines, Inc. | Class B Pass Through Certificates One | November 2017 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 236 |  |
Final expected distribution date | 2025-10 |  |
Stated interest rate | 3.65% |  |
Total debt recorded | $ 236 |  |
Proceeds received from issuance of debt | 236 |  |
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% |  |
Remaining proceeds from issuance of debt to be received in future periods | $ 677 |  |
United Airlines, Inc. | Class AA Pass Through Certificates | September 2016 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 637 |  |
Final expected distribution date | 2028-10 |  |
Stated interest rate | 2.875% |  |
Total debt recorded | $ 637 |  |
Proceeds received from issuance of debt | 557 |  |
United Airlines, Inc. | Class AA Pass Through Certificates | June 2016 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 729 |  |
Final expected distribution date | 2028-07 |  |
Stated interest rate | 3.10% |  |
Total debt recorded | $ 729 |  |
Proceeds received from issuance of debt | 319 |  |
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% |  |
Remaining proceeds from issuance of debt to be received in future periods | $ 258 |  |
United Airlines, Inc. | Class A Pass Through Certificates | September 2016 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 283 |  |
Final expected distribution date | 2028-10 |  |
Stated interest rate | 3.10% |  |
Total debt recorded | $ 283 |  |
Proceeds received from issuance of debt | 247 |  |
United Airlines, Inc. | Class A Pass Through Certificates | June 2016 |  |  |
Debt Instrument [Line Items] |  |  |
Principal | $ 324 |  |
Final expected distribution date | 2028-07 |  |
Stated interest rate | 3.45% |  |
Total debt recorded | $ 324 |  |
Proceeds received from issuance of debt | 142 |  |
United Airlines, Inc. | EETC |  |  |
Debt Instrument [Line Items] |  |  |
Principal | 3,402 |  |
Total debt recorded | 2,467 |  |
Proceeds received from issuance of debt | 1,759 |  |
Remaining proceeds from issuance of debt to be received in future periods | $ 935 |  |

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