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Years remaining on debt instruments.

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Number of Aircraft Expected to Be Delivered

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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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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

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The minimum number of units that must be purchased, in connection with an unconditional purchase obligation that has not been recognized for financial reporting purposes.

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Commitments and Contingencies - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($) employee aircraft	Jul. 31, 2018 aircraft
Commitments and Contingencies [Line Items]
Operating leases obligations	$ 13,275
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Principal	$ 1,161
Number of employees \| employee	91,400
Percentage of employees represented by various U.S. labor organizations	80.00%
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	454
Floating Rate Debt
Commitments and Contingencies [Line Items]
Principal	3,300
Fixed Rate Debt
Commitments and Contingencies [Line Items]
Principal	44
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance	3,200
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	$ 151
Maximum
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
Maximum \| Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
Boeing 787
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| aircraft	3
Boeing 737 MAX
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| aircraft	4
Boeing 777-300ER Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2018 \| aircraft	1
Boeing 767-300ER Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2018 \| aircraft	3
Embraer E175 \| Subsequent Event
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase \| aircraft		25
Airbus A319 Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase \| aircraft	20
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 \| Minimum \| May 2018 Facility and Other Operating Leases
Commitments and Contingencies [Line Items]
Operating lease agreement term	15 years
Chicago O'Hare International Airport \| Maximum \| May 2018 Facility and Other Operating Leases
Commitments and Contingencies [Line Items]
Operating lease agreement term	30 years