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

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Commitments and Contingencies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Employee Option Aircraft	Feb. 28, 2018 USD ($)
Commitments and Contingencies [Line Items]
Aggregate balance	$ 11,500,000,000
Number of call options to purchase regional jet aircraft \| Option	257
Subsequent Event \| EETC
Commitments and Contingencies [Line Items]
Debt instrument principal amount		$ 935,000,000
Boeing 737 MAX Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	10
Boeing 787 Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	7
Boeing 777-300ER Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircrafts expects to take delivery \| Aircraft	4
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	$ 157,000,000
Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	1,800,000,000
Operating leases obligations	1,400,000,000
Capital leases obligations	441,000,000
Tax-exempt special facilities revenue bonds \| Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure	244,000,000
Contingent liabilities based on participation	1,500,000,000
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	60,000,000
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance	$ 3,300,000,000
Minimum \| Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2019
Minimum \| Tax-exempt special facilities revenue bonds \| Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2022
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 \| Tax-exempt special facilities revenue bonds \| Indirect Guarantee of Indebtedness
Commitments and Contingencies [Line Items]
Debt instrument maturity year	2049
Maximum \| Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Debt instrument, remaining terms (years)	11 years
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 497,000,000
Number of employees \| Employee	89,800
Percentage of employees represented by various U.S. labor organizations	80.00%
United Airlines, Inc. \| EETC
Commitments and Contingencies [Line Items]
Debt instrument principal amount	$ 3,402,000,000