SEGMENT INFORMATION - Segment Financial Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total sales	$ 2,663	$ 2,550	$ 7,804	$ 7,151
Income (loss) from operations	433	370	1,275	958
Interest expense and other, net	(55)	(50)	(149)	(146)
Income before income taxes	378	320	1,126	812
Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,930	1,881	5,674	5,134
Transit Segment
Segment Reporting Information [Line Items]
Total sales	733	669	2,130	2,017
Corporate Activities and Elimination
Segment Reporting Information [Line Items]
Total sales	(35)	(27)	(81)	(78)
Income (loss) from operations	(36)	(25)	(109)	(70)
Interest expense and other, net	(55)	(50)	(149)	(146)
Income before income taxes	(91)	(75)	(258)	(216)
Corporate Activities and Elimination | Freight Segment
Segment Reporting Information [Line Items]
Total sales	12	18	37	47
Corporate Activities and Elimination | Transit Segment
Segment Reporting Information [Line Items]
Total sales	23	9	44	31
Operating Segments | Freight Segment
Segment Reporting Information [Line Items]
Total sales	1,942	1,899	5,711	5,181
Income (loss) from operations	390	325	1,149	820
Interest expense and other, net	0	0	0	0
Income before income taxes	390	325	1,149	820
Operating Segments | Transit Segment
Segment Reporting Information [Line Items]
Total sales	756	678	2,174	2,048
Income (loss) from operations	79	70	235	208
Interest expense and other, net	0	0	0	0
Income before income taxes	$ 79	$ 70	$ 235	$ 208