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Pension and Other Postretirement Plans - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items] |  |  |
Effect on post retirement benefit obligation, 1% Decrease | $ 139 |  |
Effect on total service and interest cost, 1% Decrease | 10 |  |
Profit sharing and payroll tax expense | $ 334 | $ 349 | $ 628
Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percentage of pre-tax earnings paid for profit sharing plan | 5.00% |  |
Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percentage of pre-tax earnings paid for profit sharing plan | 20.00% |  |
IAM National Pension Plan | Multi-Employer Pension Plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Multi-employer plan contributions |  | $ 435 |
IAM National Pension Plan | Multi-Employer Pension Plans | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percent of company's contribution to plan |  | 5.00% |
United Airlines, Inc. |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Expense for defined contribution plans | $ 693 | $ 656 | $ 592
United Airlines, Inc. | Minimum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employer contribution percentage | 1.00% |  |
United Airlines, Inc. | Maximum |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Employer contribution percentage | 16.00% |  |
Pension Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Expected employer contributions to pension and postretirement plans | $ 318 |  |
Other Postretirement Benefits |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Expected employer contributions to pension and postretirement plans | $ 95 |  |
Other Postretirement Benefits | Deposit Administration Fund |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Percent of plan assets invested | 100.00% |  |

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- Definition Amount of decrease in accumulated postretirement benefit obligation from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of decrease in service and interest cost components of net periodic postretirement benefit cost from one-percentage-point decrease in assumed health care cost trend rate. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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