Details of Pass Through Trusts (Detail) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Proceeds received from issuance of debt	$ 2,119	$ 510
United Airlines, Inc.
Debt Instrument [Line Items]
Principal	392
Proceeds received from issuance of debt	2,119	$ 510
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	$ 637
Proceeds received from issuance of debt	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	$ 729
Proceeds received from issuance of debt	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	$ 283
Proceeds received from issuance of debt	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	$ 324
Proceeds received from issuance of debt	142
United Airlines, Inc. \| EETC
Debt Instrument [Line Items]
Principal	1,973
Total debt recorded	1,973
Proceeds received from issuance of debt	$ 1,265

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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-Name Accounting Standards Codification
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+ 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

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
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-Section 45
-Paragraph 14
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