RESTRUCTURING - Schedule of Restructuring Charges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	$ 10	$ 13	$ 22	$ 30
Freight Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	2	3	2	7
Transit Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	8	10	20	23
Cost of goods sold | Freight Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	2	2	6	4
Cost of goods sold | Transit Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	5	11	9	17
Selling, general and administrative expenses | Freight Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	0	1	0	3
Selling, general and administrative expenses | Transit Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	3	(1)	9	4
Other income, net | Freight Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	0	0	(4)	0
Amortization expense | Transit Segment
Restructuring Cost and Reserve [Line Items]
Total Integration 2.0 restructuring charges	$ 0	$ 0	$ 2	$ 2