SEGMENT INFORMATION - Schedule of Segment Financial Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
Segment Reporting Information [Line Items]
Total sales	$ 2,950	$ 2,610
Cost of sales	(1,889)	(1,710)
Gross profit	1,061	900
Selling, general & administrative expenses	(401)	(307)
Engineering expenses	(56)	(46)
Amortization expense	(87)	(73)
Income (loss) from operations	517	474
Interest expense and other, net	(48)	(48)
Income before income taxes	469	426
Depreciation and amortization	139	120
Capital expenditures	46	44
Segment assets	23,196	19,096	$ 22,069
Intersegment eliminations
Segment Reporting Information [Line Items]
Total sales	(24)	(20)
Corporate Activities and Elimination
Segment Reporting Information [Line Items]
Total sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general & administrative expenses	(54)	(36)
Engineering expenses	0	0
Amortization expense	0	0
Income (loss) from operations	(54)	(36)
Interest expense and other, net	(48)	(48)
Income before income taxes	(102)	(84)
Depreciation and amortization	3	3
Capital expenditures	1	3
Segment assets	1,523	1,727
Freight Segment
Segment Reporting Information [Line Items]
Total sales	2,115	1,901
Freight Segment | Operating Segments
Segment Reporting Information [Line Items]
Total sales	2,115	1,901
Cost of sales	(1,327)	(1,216)
Gross profit	$ 788	$ 685
Gross margin	37.30%	36.00%
Selling, general & administrative expenses	$ (219)	$ (164)
Engineering expenses	(43)	(36)
Amortization expense	(76)	(65)
Income (loss) from operations	450	420
Interest expense and other, net	0	0
Income before income taxes	450	420
Depreciation and amortization	112	97
Capital expenditures	27	31
Segment assets	16,002	13,224
Freight Segment | Intersegment eliminations
Segment Reporting Information [Line Items]
Total sales	14	11
Transit Segment
Segment Reporting Information [Line Items]
Total sales	835	709
Transit Segment | Operating Segments
Segment Reporting Information [Line Items]
Total sales	835	709
Cost of sales	(562)	(494)
Gross profit	$ 273	$ 215
Gross margin	32.70%	30.30%
Selling, general & administrative expenses	$ (128)	$ (107)
Engineering expenses	(13)	(10)
Amortization expense	(11)	(8)
Income (loss) from operations	121	90
Interest expense and other, net	0	0
Income before income taxes	121	90
Depreciation and amortization	24	20
Capital expenditures	18	10
Segment assets	5,671	4,145
Transit Segment | Intersegment eliminations
Segment Reporting Information [Line Items]
Total sales	$ 10	$ 9