Statements of Consolidated Stockholders' Equity - USD ($) $ in Millions	Total		United Airlines, Inc.		Adoption of New Accounting Standard	[1]	Adoption of New Accounting Standard United Airlines, Inc.	[2]	Additional Capital Invested	Additional Capital Invested United Airlines, Inc.	Retained Earnings	Retained Earnings United Airlines, Inc.	Retained Earnings Adoption of New Accounting Standard	[1]	Retained Earnings Adoption of New Accounting Standard United Airlines, Inc.	[2]	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) United Airlines, Inc.	(Receivable from) Payable to Related Parties, Net United Airlines, Inc.
Balance at Dec. 31, 2018	$ 10,042		$ 10,004						$ 6,120	$ 598	$ 6,715	$ 10,319					$ (803)	$ (803)	$ (110)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	3,009		3,011								3,009	3,011
Other comprehensive income (loss)	85		85														85	85
Dividend to UAL			(1,641)							(664)		(977)
Stock-settled share-based compensation	66		66						66	66
Other			(33)																(33)
Balance at Dec. 31, 2019	11,531		11,492						6,129	0	9,716	12,353					(718)	(718)	(143)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(7,069)		(7,067)								(7,069)	(7,067)
Other comprehensive income (loss)	(421)		(421)														(421)	(421)
Dividend to UAL			(342)							(12)		(330)
Stock-settled share-based compensation	97		97						97	97
Impact of UAL common stock issuance	2,103		2,103						2,102										2,103
Other			83																83
Balance at Dec. 31, 2020	$ 5,960		$ 5,928		$ (17)		$ (17)		8,366	85	2,626	4,939	$ (17)		$ (17)		(1,139)	(1,139)	2,043
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]	[1]	Accounting Standards Update 2016-13 [Member]	[2]
Net income (loss)	$ (1,964)		$ (1,962)								(1,964)	(1,962)
Other comprehensive income (loss)	197		197														197	197
Stock-settled share-based compensation	232		232						232	232		0
Impact of UAL common stock issuance	532		532						532										532
Other			71																71
Balance at Dec. 31, 2021	$ 5,029		$ 4,998						$ 9,156	$ 317	$ 625	$ 2,977					$ (942)	$ (942)	$ 2,646

[1] Transition adjustment due to the adoption of Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses.

[2] Transition adjustment due to the adoption of Accounting Standards Update No. 2016-13, Financial Instruments—Credit Losses.