Commitments and Contingencies - Additional Information (Detail)		3 Months Ended	9 Months Ended
	Feb. 17, 2017 Aircraft	Sep. 30, 2017 USD ($) Employee Aircraft	Sep. 30, 2017 USD ($) Employee Aircraft
Commitments and Contingencies [Line Items]
Aggregate balance		$ 12,000,000,000	$ 12,000,000,000
Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure		1,800,000,000	1,800,000,000
Operating leases obligations		1,400,000,000	1,400,000,000
Capital leases obligations		441,000,000	441,000,000
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount		3,300,000,000	3,300,000,000
Fixed Rate Debt
Commitments and Contingencies [Line Items]
Debt instrument principal amount		68,000,000	68,000,000
Loans And Leases From Non U S Entities
Commitments and Contingencies [Line Items]
Aggregate balance		3,200,000,000	3,200,000,000
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Guarantor obligations, maximum exposure		$ 159,000,000	$ 159,000,000
Minimum | Tax-exempt special facilities revenue bonds
Commitments and Contingencies [Line Items]
Debt instrument maturity year			2019
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
Air Wisconsin | Maximum | CRJ 200
Commitments and Contingencies [Line Items]
Number of aircraft to operate | Aircraft	65
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Number of aircrafts under the extended term of contract | Aircraft		125
Capacity purchase agreement contract expiration date after extension		Dec. 31, 2022
Debt instrument maturity year			2027
Debt instrument principal amount		$ 392,000,000	$ 392,000,000
Number of employees | Employee		89,700	89,700
Percentage of employees represented by various U.S. labor organizations			80.00%
United Airlines, Inc. | Turboprop Aircraft [Member]
Commitments and Contingencies [Line Items]
Number of aircraft to be retire from service | Aircraft		21	21
United Airlines, Inc. | Delivered in Last Three Months of 2017 | Embraer E175 Aircraft
Commitments and Contingencies [Line Items]
Number of additional aircraft ordered for future delivery | Aircraft		5	5
United Airlines, Inc. | Capital Addition Purchase Commitments
Commitments and Contingencies [Line Items]
New aircraft, scheduled delivery date			2027
United Airlines, Inc. | Capital Addition Purchase Commitments | Embraer E175 Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2017 | Aircraft		5	5
United Airlines, Inc. | Capital Addition Purchase Commitments | A319 aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2017 | Aircraft		4	4
United Airlines, Inc. | Capital Addition Purchase Commitments | Airbus A320 Aircraft
Commitments and Contingencies [Line Items]
Number of aircraft expected to be delivered through the remainder of 2017 | Aircraft		2	2