Commitments and Contingencies - Narrative (Details) $ / shares in Units, employee in Thousands, shares in Millions, $ in Millions	9 Months Ended
	Sep. 30, 2019 USD ($) employee commitment aircraft	Dec. 31, 2019 flight	Oct. 04, 2019 USD ($)	Mar. 13, 2019 aircraft	Mar. 12, 2019 flight	Dec. 31, 2018 USD ($)	Nov. 30, 2018 USD ($) $ / shares shares	Sep. 30, 2018 aircraft
Commitments and Contingencies [Line Items]
Remaining term of debt	11 years
Aggregate balance	$ 12,300
United Airlines, Inc.
Commitments and Contingencies [Line Items]
Number of employees | employee	95
Percentage of employees represented by various U.S. labor organizations	84.00%
AVH Senior Secured Convertible Loan | Subsequent Event
Commitments and Contingencies [Line Items]
Commitment amount (at least)			$ 150
AVH Senior Secured Convertible Loan | United Airline Holdings and Kingsland Holdings Limited | Subsequent Event
Commitments and Contingencies [Line Items]
Commitment amount (at least)			$ 250
Kingsland
Commitments and Contingencies [Line Items]
Number of shares that may be put to United (in shares) | shares							144.8
Number of ADRs that may be put into United (in shares) | shares							18.1
Market price of common stock at fifth anniversary (in dollars per share) | $ / shares							$ 12
Aggregate maximum possible combined put payment and guarantee amount							$ 217
Liability for the fair value of guarantees						$ 31
Tax-Exempt Special Facilities Revenue Bonds
Commitments and Contingencies [Line Items]
Aggregate principal amount of guarantee	$ 1,900
Floating Rate Debt
Commitments and Contingencies [Line Items]
Debt	$ 3,400
Loans and Leases from Non-U.S. Entities
Commitments and Contingencies [Line Items]
Remaining term of debt	11 years
Aggregate balance	$ 3,100
Aircraft Mortgage Debt
Commitments and Contingencies [Line Items]
Aggregate principal amount of guarantee	$ 136
Airbus A319
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase | aircraft	20
Boeing 737-700
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase | aircraft	20
Boeing 737 MAX
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase | commitment	171
Number of aircraft grounded under emergency order | aircraft				14
Number of flights operated using grounded aircraft | flight					50
Boeing 737 MAX | Forecast
Commitments and Contingencies [Line Items]
Number of expected flights operating per day prior to grounding order | flight		110
Embraer E175
Commitments and Contingencies [Line Items]
Number of aircraft committed to purchase | commitment	29
Embraer ERJ 145
Commitments and Contingencies [Line Items]
Number of leased aircraft | aircraft								54
Number of aircraft purchased | aircraft	36