Common Stockholders' Equity and Preferred Securities	12 Months Ended
Common Stockholders' Equity and Preferred Securities	Dec. 31, 2020
Equity [Abstract]
Common Stockholders' Equity and Preferred Securities	COMMON STOCKHOLDERS' EQUITY AND PREFERRED SECURITIES On February 24, 2020, the Company suspended share repurchases under its share repurchase program authorized by UAL's Board of Directors in July 2019. UAL's Board of Directors subsequently terminated this share repurchase program on April 24, 2020. In 2020, UAL repurchased approximately 4 million shares of UAL common stock in open market transactions for $0.3 billion. See Part II, Item 5, Market for Registrant's Common Equity, Related Stockholder Matters and Issuer Purchases of Equity Securities, of this report for additional information. On April 20, 2020, UAL entered into a warrant agreement with Treasury, pursuant to which UAL agreed to issue to Treasury warrants to purchase up to approximately 4.6 million shares of common stock, pro rata in conjunction with increases to the principal amount outstanding under the PSP Note (the "PSP Warrants"), with an initial issuance of warrants to purchase up to approximately 2.3 million shares of common stock. As of December 31, 2020, UAL has issued PSP Warrants to purchase up to approximately 4.8 million shares of common stock, with such warrants accounted for as equity instruments. The PSP Warrants have a strike price of $31.50 per share (which was the closing price of UAL's common stock on The Nasdaq Stock Market on April 9, 2020). The PSP Warrants will expire five years after issuance, and are exercisable either through net share settlement, in cash or in shares of UAL common stock, at UAL's option. The relative fair value of the PSP Warrants was calculated using a Black-Scholes options pricing model and approximately $66 million was recorded within stockholders' equity with an offset to the CARES Act grant credit. The PSP Warrants contain customary anti-dilution provisions and registration rights and are freely transferable. Pursuant to the terms of the PSP Warrants, PSP Warrant holders do not have any voting rights. In connection with the entry into the Term Loan Facility, UAL entered into a warrant agreement with Treasury on September 28, 2020, pursuant to which UAL will issue to Treasury warrants (the "Credit Agreement Warrants") to purchase up to approximately 16.4 million shares of UAL common stock, assuming United borrows the initial commitments under the Term Loan Facility in full. The Credit Agreement Warrants will be issued on the date of disbursement of each Term Loan in an amount corresponding to 10% of the principal amount of each such disbursement. In connection with United's borrowing of the initial $520 million loan, on September 28, 2020, UAL issued Credit Agreement Warrants to purchase up to approximately 1.7 million shares of UAL common stock. The Credit Agreement Warrants will have a strike price of $31.50 per share. The Credit Agreement Warrants will expire five years after issuance, and are exercisable either through net share settlement in cash or in shares of UAL common stock, at UAL's option. The relative fair value of the Credit Agreement Warrants was calculated using a Black-Scholes options pricing model and approximately $30 million was recorded within stockholders' equity and as a debt discount against the outstanding loan. If Treasury increases its loan commitments, then the maximum amount of common stock for which warrants could be issued would increase proportionally with such increase to the commitments. During the first quarter of 2021, UAL entered into a warrant agreement with Treasury pursuant to which UAL will issue to Treasury warrants to purchase up to approximately 1.7 million shares of UAL common stock, pro rata in conjunction with increases to the principal amount outstanding under the PSP2 Note (the "PSP2 Warrants"). The PSP2 Warrants will have a strike price of $43.26 per share. The PSP2 Warrants will expire five years after issuance, and are exercisable either through net share settlement in cash or in shares of UAL common stock, at UAL's option. The PSP2 Warrants contain customary anti-dilution provisions, registration rights and are freely transferable. Pursuant to the terms of the PSP2 Warrants, PSP2 Warrant holders do not have any voting rights. In 2020, UAL entered into an underwriting agreement (the "Underwriting Agreement") with Morgan Stanley & Co. LLC and Barclays Capital Inc. (collectively, the "Underwriters"), relating to the issuance and sale by UAL of approximately 43 million shares of its common stock, par value $0.01 per share, at a price to the public of $26.50 per share, resulting in total proceeds of approximately $1.1 billion. On June 15, 2020, UAL entered into an equity distribution agreement (the "Distribution Agreement") with Citigroup Global Markets Inc., BofA Securities, Inc. and J.P. Morgan Securities LLC (collectively, the "Managers"), relating to the issuance and sale from time to time by UAL (the "ATM Offering"), through the Managers, of up to 28 million shares of UAL's common stock, par value $0.01 per share. Sales of the shares, if any, under the Distribution Agreement may be made in any transactions that are deemed to be "at the market offerings" as defined in Rule 415 under the Securities Act of 1933, as amended. Under the terms of the Distribution Agreement, UAL may also sell shares to any Manager, as principal for its own account, at a price agreed upon at the time of sale. If UAL sells shares to a Manager as principal, UAL will enter into a separate agreement with such Manager. As of December 31, 2020, approximately 21.4 million shares were sold in the ATM Offering at an average price of $46.70 per share, with net proceeds to the Company totaling approximately $989 million. At December 31, 2020, approximately 6 million shares of UAL's common stock were reserved for future issuance related to the issuance of equity-based awards under the Company's incentive compensation plans. As of December 31, 2020, UAL had two shares of junior preferred stock (par value $0.01 per share) outstanding. In addition, UAL is authorized to issue 250 million shares of preferred stock (without par value) under UAL's amended and restated certificate of incorporation.