INTANGIBLES - Change in the Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020
Goodwill [Roll Forward]
Balance beginning of period	$ 8,485	$ 8,361
Additions	229	2
Disposals		(6)
Foreign currency impact	(127)	128
Balance end of period	8,587	8,485
Freight Segment
Goodwill [Roll Forward]
Balance beginning of period	6,872	6,877
Additions	214	2
Disposals		(6)
Foreign currency impact	(13)	(1)
Balance end of period	7,073	6,872
Transit Segment
Goodwill [Roll Forward]
Balance beginning of period	1,613	1,484
Additions	15	0
Disposals		0
Foreign currency impact	(114)	129
Balance end of period	$ 1,514	$ 1,613

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of divestiture of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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