GOODWILL AND INTANGIBLE ASSETS - Summary of Change in the Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Goodwill [Roll Forward]
Balance beginning of period	$ 8,780	$ 8,508
Additions	85	215
Disposals	(6)	(4)
Foreign currency impact	(149)	61
Balance end of period	8,710	8,780
Freight Segment
Goodwill [Roll Forward]
Balance beginning of period	7,294	7,067
Additions	31	215
Disposals	(5)	(4)
Foreign currency impact	(72)	16
Balance end of period	7,248	7,294
Transit Segment
Goodwill [Roll Forward]
Balance beginning of period	1,486	1,441
Additions	54	0
Disposals	(1)	0
Foreign currency impact	(77)	45
Balance end of period	$ 1,462	$ 1,486