Combined Notes to the Financial Statements (Unaudited) (Details) employee in Thousands					1 Months Ended	2 Months Ended	3 Months Ended			6 Months Ended
	Jul. 08, 2020 employee	Jul. 02, 2020 USD ($)	Apr. 20, 2020 USD ($)	Apr. 17, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2020	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jul. 02, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)		Jun. 15, 2020 shares	Dec. 31, 2019 USD ($)
Unusual or Infrequent Item, or Both [Line Items]
Net income (loss)								$ (1,627,000,000)	$ 1,052,000,000		$ (3,331,000,000)	$ 1,344,000,000
Percent of capacity cut								88.00%
Rolling cancellation period											60 days
Proceeds from issuance of long-term debt											$ 1,669,000,000	996,000,000
Proceeds from the issuance of common stock											1,100,000,000
Payroll taxes deferred under the CARES Act											78,000,000
Total funding provided under the Payroll Support Program			$ 5,000,000,000.0		$ 5,000,000,000.0	$ 5,000,000,000.0		$ 5,000,000,000.0			5,000,000,000.0
Funding provided through direct grants under the Payroll Support Program			3,500,000,000
Funding provided through loans under the Payroll Support Program			$ 1,500,000,000
Support funding received						4,500,000,000
Portion of grant recognized as a credit to special charges								1,589,000,000	0		1,589,000,000	0
Payroll Support Program deferred credit					1,508,000,000	1,508,000,000		1,508,000,000			1,508,000,000				$ 0
Remaining balance yet to be received					500,000,000	500,000,000		500,000,000			500,000,000
Forecast
Unusual or Infrequent Item, or Both [Line Items]
Percent of capacity cut							65.00%
Subsequent Event | Forecast
Unusual or Infrequent Item, or Both [Line Items]
Number of employees notified of plans for workforce reduction | employee	36,000
Equity Distribution Agreement
Unusual or Infrequent Item, or Both [Line Items]
Proceeds from the issuance of common stock					22,000,000
Number of shares issuable under Equity Distribution Agreement (up to) (in shares) | shares														28,000,000
Notes, Secured Term Loans and Aircraft Financing
Unusual or Infrequent Item, or Both [Line Items]
Proceeds from issuance of long-term debt											3,000,000,000.0
Notes, Secured Term Loans and Aircraft Financing | Subsequent Event
Unusual or Infrequent Item, or Both [Line Items]
Proceeds from issuance of long-term debt										$ 10,000,000,000.0
Secured Debt and Term Loan
Unusual or Infrequent Item, or Both [Line Items]
Proceeds from issuance of long-term debt											6,800,000,000
Secured Debt
Unusual or Infrequent Item, or Both [Line Items]
Expected borrowings				$ 4,500,000,000
Expected term of debt				5 years
Secured Debt | PSP Note
Unusual or Infrequent Item, or Both [Line Items]
Face amount					$ 1,300,000,000	$ 1,300,000,000		$ 1,300,000,000			$ 1,300,000,000
Unsecured Debt | PSP Note
Unusual or Infrequent Item, or Both [Line Items]
Term of debt			10 years					10 years
Percent increase in the principal amount based on any disbursement made by the U.S. Treasury Department					30.00%	30.00%		30.00%			30.00%
U.S. Department of Treasury Warrants
Unusual or Infrequent Item, or Both [Line Items]
Warrants oustanding					$ 57,000,000	$ 57,000,000		$ 57,000,000			$ 57,000,000
CEO and President
Unusual or Infrequent Item, or Both [Line Items]
Voluntary pay reduction											100.00%
Non-Employee Directors
Unusual or Infrequent Item, or Both [Line Items]
Voluntary pay reduction											100.00%
United Airlines, Inc.
Unusual or Infrequent Item, or Both [Line Items]
Net income (loss)								(1,626,000,000)	$ 1,052,000,000		$ (3,330,000,000)	1,345,000,000	[1]
Proceeds from issuance of long-term debt											1,669,000,000	$ 996,000,000
Payroll Support Program deferred credit					$ 1,508,000,000	$ 1,508,000,000		$ 1,508,000,000			$ 1,508,000,000				$ 0
Revolving Credit Facility | United Airlines, Inc. | Secured Debt | Subsequent Event
Unusual or Infrequent Item, or Both [Line Items]
Amount available under credit facility		$ 2,000,000,000.0								$ 2,000,000,000.0
LIBOR | Revolving Credit Facility | United Airlines, Inc. | Secured Debt | Subsequent Event
Unusual or Infrequent Item, or Both [Line Items]
Proceeds from lines of credit		$ 1,000,000,000.0

[1] Transition adjustment due to the adoption of Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses. See Note 1 to the financial statements contained in Part I, Item 1 of this report for additional information.