Debt Instrument Date Principal Due

No definition available.

Name:	ual_DebtInstrumentDatePrincipalDue
Namespace Prefix:	ual_
Data Type:	xbrli:gYearMonthItemType
Balance Type:	na
Period Type:	duration

- 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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Namespace Prefix:	ual_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

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

- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3255-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Financing Activities
-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

Name:	us-gaap_ProceedsFromIssuanceOfLongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=ual_UnitedAirLinesIncMember
Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=ual_ClassAAPassThroughCertificatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ual_PeriodAxis=ual_SeptemberTwentySixteenMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	ual_PeriodAxis=ual_JuneTwentySixteenMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=ual_ClassAPassThroughCertificatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_EnhancedEquipmentTrustCertificateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Details of Pass Through Trusts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total debt recorded			$ 248
Proceeds received from issuance of debt	$ 808	$ 1,073	1,432
United Airlines, Inc.
Debt Instrument [Line Items]
Principal	369
Proceeds received from issuance of debt	808	$ 1,073	$ 1,432
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	$ 80
Proceeds received from issuance of debt	80
Remaining proceeds from issuance of debt to be received in future periods	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	$ 410
Proceeds received from issuance of debt	410
Remaining proceeds from issuance of debt to be received in future periods	319
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	$ 36
Proceeds received from issuance of debt	36
Remaining proceeds from issuance of debt to be received in future periods	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	$ 182
Proceeds received from issuance of debt	182
Remaining proceeds from issuance of debt to be received in future periods	142
United Airlines, Inc. \| EETC
Debt Instrument [Line Items]
Principal	1,973
Total debt recorded	708
Proceeds received from issuance of debt	708
Remaining proceeds from issuance of debt to be received in future periods	$ 1,265