Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 7,166	$ 18,283	$ 11,269
Restricted cash	45	37	255
Other assets:
Restricted cash	210	213	218
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	7,421	18,533	11,742	$ 2,868
United Airlines, Inc.
Current assets:
Cash and cash equivalents	7,166	18,283
Other assets:
Total cash, cash equivalents and restricted cash shown in the statement of consolidated cash flows	$ 7,421	$ 18,533	$ 11,742	$ 2,862