Unusual or Infrequently Occurring Items (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Unusual or Infrequent Item, or Both [Line Items]
Special items - Impairment charges and other	$ 74	$ 156	$ 254	$ 406
Special items - net non-operating	1	8	1	14
Fleet transition - impairment [Member]
Unusual or Infrequent Item, or Both [Line Items]
Special items - Impairment charges and other	(16)	$ 156	51	355
Litigation
Unusual or Infrequent Item, or Both [Line Items]
Special items - Impairment charges and other			45
Wages and Benefits [Member]
Unusual or Infrequent Item, or Both [Line Items]
Special items - Impairment charges and other			30	$ 51
Integration costs
Unusual or Infrequent Item, or Both [Line Items]
Special items - Impairment charges and other	$ 90		$ 128