Pension, Postretirement And Other Employee Benefit Plans - Allocation of Plan Assets (Details) - United Airlines, Inc.	12 Months Ended
Dec. 31, 2023
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	9.00%
Equity securities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	25.00%
Equity securities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	73.00%
Fixed-income securities
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	8.00%
Fixed-income securities \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	14.00%
Fixed-income securities \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	53.00%
Alternatives
Defined Benefit Plan Disclosure [Line Items]
Expected Long-Term Rate of Return	8.00%
Alternatives \| Minimum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	3.00%
Alternatives \| Maximum
Defined Benefit Plan Disclosure [Line Items]
Percent of Total	27.00%

Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-8

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (k)(3)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480482/715-20-55-17

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

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