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Debt - Details of Past Through Trusts (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Feb. 28, 2018
Debt Instrument [Line Items] |  |  |  |  |  |
Proceeds received from issuance of debt | $ 1,740,000,000 | $ 2,765,000,000 | [1] | $ 808,000,000 | [1] |
EETC |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal |  |  |  |  |  | $ 1,000,000,000.0
United Airlines, Inc. |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | 424,000,000 |  |  |  |  |
Proceeds received from issuance of debt | 1,740,000,000 | $ 2,765,000,000 | [2] | $ 808,000,000 | [2] |
United Airlines, Inc. | EETC |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | 2,174,000,000 |  |  |  |  |
Total debt recorded | 1,161,000,000 |  |  |  |  |
Proceeds received from issuance of debt | 1,161,000,000 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | 1,013,000,000 |  |  |  |  |
United Airlines, Inc. | AA | February 2019 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | $ 717,000,000 |  |  |  |  |
Stated interest rate | 4.15% |  |  |  |  |
Total debt recorded | $ 0 |  |  |  |  |
Proceeds received from issuance of debt | 0 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | 717,000,000 |  |  |  |  |
United Airlines, Inc. | AA | February 2018 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | $ 677,000,000 |  |  |  |  |
Stated interest rate | 3.50% |  |  |  |  |
Total debt recorded | $ 677,000,000 |  |  |  |  |
Proceeds received from issuance of debt | 677,000,000 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | 0 |  |  |  |  |
United Airlines, Inc. | A |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | $ 296,000,000 |  |  |  |  |
Stated interest rate | 4.55% |  |  |  |  |
Total debt recorded | $ 0 |  |  |  |  |
Proceeds received from issuance of debt | 0 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | 296,000,000 |  |  |  |  |
United Airlines, Inc. | A | February 2018 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | $ 258,000,000 |  |  |  |  |
Stated interest rate | 3.70% |  |  |  |  |
Total debt recorded | $ 258,000,000 |  |  |  |  |
Proceeds received from issuance of debt | 258,000,000 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | 0 |  |  |  |  |
United Airlines, Inc. | B | May 2018 |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |
Principal | $ 226,000,000 |  |  |  |  |
Stated interest rate | 4.60% |  |  |  |  |
Total debt recorded | $ 226,000,000 |  |  |  |  |
Proceeds received from issuance of debt | 226,000,000 |  |  |  |  |
Remaining proceeds from issuance of debt to be received in future periods | $ 0 |  |  |  |  |
[1] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.
[2] | Amounts adjusted due to the adoption of Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (Topic 606). See Note 1 to the financial statements contained in Part II, Item 8 of this report for additional information.

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- Definition Amount of borrowing capacity currently available under the debt instrument (initial borrowing capacity less the amount of proceeds received). + References No definition available. + Details
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- Definition Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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