Income Taxes - Temporary Differences and Carryforwards Giving Rise to Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Deferred income tax asset (liability):
Federal and state net operating loss ("NOL") carryforwards	$ 2,932	$ 2,229
Deferred revenue	1,783	2,349
Employee benefits, including pension, postretirement and medical	606	986
Operating lease liabilities	1,118	1,272
Other financing liabilities	141	327
Interest expense carryforward	510	0
Other	576	535
Less: Valuation allowance	(199)	(210)
Total deferred tax assets	7,467	7,488
Depreciation	(5,844)	(5,122)
Operating lease right-of-use asset	(881)	(1,051)
Intangibles	(651)	(656)
Total deferred tax liabilities	(7,376)	(6,829)
Net deferred tax asset	91	659
United Airlines, Inc.
Deferred income tax asset (liability):
Federal and state net operating loss ("NOL") carryforwards	2,903	2,201
Deferred revenue	1,783	2,349
Employee benefits, including pension, postretirement and medical	606	986
Operating lease liabilities	1,118	1,272
Other financing liabilities	141	327
Interest expense carryforward	510	0
Other	576	535
Less: Valuation allowance	(199)	(210)
Total deferred tax assets	7,438	7,460
Depreciation	(5,844)	(5,122)
Operating lease right-of-use asset	(881)	(1,051)
Intangibles	(651)	(656)
Total deferred tax liabilities	(7,376)	(6,829)
Net deferred tax asset	$ 62	$ 631