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Pension and Other Postretirement Plans (Multi-Employer Plans) - Additional Information (Detail) - Multiemployer Plans, Pension - IAM National Pension Plan $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)
Multiemployer Plans [Line Items]
Multi-employer plan contributions	$ 414
Minimum
Multiemployer Plans [Line Items]
Percent of company's contribution to plan	5.00%

X

- Definition

Multiemployer Pension Employer Percentage

+ References

No definition available.

+ Details

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Namespace Prefix:	ual_
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Balance Type:	na
Period Type:	duration

X

- 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.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of contributions made to multiemployer plan by all employers who participate in plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 7
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450678-114947

+ Details

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X

- Details

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X

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

X

- Details

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