Commitments and Contingencies - Additional Information (Detail)	3 Months Ended
Mar. 31, 2018 USD ($) Aircraft
Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	$ 2,000,000,000
Operating leases obligations	1,400,000,000
Capital leases obligations	454,000,000
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount	3,400,000,000
Fixed Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount	52,000,000
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance	3,300,000,000
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	154,000,000
Facility and Other Operating Leases
Commitments and Contingencies [Line Items]
Operating leases obligations	$ 13,095,000,000
Maximum
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
Maximum \| Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2038
Maximum \| Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
Minimum \| Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2019
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 935,000,000
Number of employees	90,800
Percentage of employees represented by various U.S. labor organizations	79.00%
Boeing 777-300ER Aircraft
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	2
Boeing 787 Aircraft
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	3
Boeing 737 MAX Aircraft
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	10
Boeing 767-300ER Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2018 \| Aircraft	3
Chicago O'Hare International Airport \| Facility and Other Operating Leases
Commitments and Contingencies [Line Items]
Operating lease agreement term	15 years
Operating lease description	A lease term of approximately 15 years effective May 12, 2018 through December 31, 2033.
Airbus A319 Aircraft
Commitments and Contingencies [Line Items]
Number of new aircraft committed to purchase \| Aircraft	20
Airbus A319 Aircraft \| Maximum
Commitments and Contingencies [Line Items]
Expected delivery date scheduled, Year	2021
Airbus A319 Aircraft \| Minimum
Commitments and Contingencies [Line Items]
Expected delivery date scheduled, Year	2020

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Commitments And Contingencies [Line Items]

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Debt instrument maturity year

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Years remaining on debt instruments.

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Number of Aircraft Expected to Be Delivered

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Number of aircrafts expected to take delivery.

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Percentage of employees represented by labor organizations

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Scheduled Delivery Year

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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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-Publisher FASB
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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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Description of lessee's operating lease.

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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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