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Years remaining on debt instruments.

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Percentage of employees represented by labor organizations

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Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

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

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Commitments and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Mar. 31, 2018	Jun. 30, 2018	Sep. 30, 2018 USD ($) employee commitment aircraft
Commitments and Contingencies [Line Items]
Operating leases obligations			$ 12,931
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Principal			$ 1,161
Number of employees \| employee			90,900
Percentage of employees represented by various U.S. labor organizations			82.00%
Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure			$ 2,000
Operating leases obligations			1,400
Capital leases obligations			466
Floating Rate Debt
Commitments and Contingencies [Line Items]
Principal			3,200
Fixed Rate Debt
Commitments and Contingencies [Line Items]
Principal			35
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance			3,100
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure			$ 148
Maximum
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)			10 years
Maximum \| Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)			10 years
Chicago O'Hare International Airport \| March 2018 Facility and Other Operating Leases
Commitments and Contingencies [Line Items]
Operating lease agreement term	15 years
Chicago O'Hare International Airport \| May 2018 Facility and Other Operating Leases \| Minimum
Commitments and Contingencies [Line Items]
Operating lease agreement term		15 years
Chicago O'Hare International Airport \| May 2018 Facility and Other Operating Leases \| Maximum
Commitments and Contingencies [Line Items]
Operating lease agreement term		30 years
Boeing 787
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| aircraft			3
Number of aircraft committed to purchase \| commitment			27
Boeing 737 MAX
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| aircraft			3
Number of aircraft committed to purchase \| commitment			154
Boeing 777-300ER Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2018 \| aircraft			1
Airbus A319 Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase \| aircraft			20
Embraer ERJ 145
Commitments and Contingencies [Line Items]
Number of leased aircraft \| aircraft			54