Statements of Consolidated Stockholders' Equity (Unaudited) - USD ($) $ in Millions	Total	Additional Capital Invested	Retained Earnings (Accumulated Deficit)	Accumulated Other Comprehensive Income (Loss)	United Airlines, Inc.	United Airlines, Inc. Additional Capital Invested	United Airlines, Inc. Retained Earnings (Accumulated Deficit)	United Airlines, Inc. Accumulated Other Comprehensive Income (Loss)	United Airlines, Inc. Payable to Parent
Balance at Dec. 31, 2020	$ 5,960	$ 8,366	$ 2,626	$ (1,139)	$ 5,928	$ 85	$ 4,939	$ (1,139)	$ 2,043
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(1,357)		(1,357)		(1,357)		(1,357)
Other comprehensive income (loss)	13			13	13			13
Stock-settled share-based compensation	32	32			32	32
Impact of UAL common stock issuance	532	532			532				532
Other					27				27
Balance at Mar. 31, 2021	5,206	8,923	1,239	(1,126)	5,175	117	3,582	(1,126)	2,602
Balance at Dec. 31, 2021	5,029	9,156	625	(942)	4,998	317	2,977	(942)	2,646
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(1,377)		(1,377)		(1,377)		(1,377)
Other comprehensive income (loss)	5			5	5			5
Stock-settled share-based compensation	38	38			38	38
Other					(71)				(71)
Balance at Mar. 31, 2022	$ 3,624	$ 8,953	$ (844)	$ (937)	$ 3,593	$ 355	$ 1,600	$ (937)	$ 2,575