Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Receivables - allowance for credit losses	$ 74	$ 78
Aircraft fuel, spare, parts and supplies - obsolescence allowance	502	478
Intangibles - accumulated amortization	1,507	1,495
Investments in affiliates and other - allowance for credit losses	$ 526	$ 522
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized (in shares)	1,000,000,000	1,000,000,000
Common shares, outstanding (in shares)	323,577,438	311,845,232
United Airlines, Inc.
Receivables - allowance for credit losses	$ 74	$ 78
Aircraft fuel, spare, parts and supplies - obsolescence allowance	502	478
Intangibles - accumulated amortization	1,507	1,495
Investments in affiliates and other - allowance for credit losses	$ 526	$ 522
Common stock, par value (in dollars per share)	$ 10,000.00	$ 10,000.00
Common shares, authorized (in shares)	1,000	1,000
Common shares, issued (in shares)	1,000	1,000
Common shares, outstanding (in shares)	1,000	1,000