GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Goodwill (Details) $ in Millions	3 Months Ended
	Mar. 31, 2026 USD ($)
Goodwill [Roll Forward]
Beginning balance	$ 1,814
Foreign currency translation	(14)
Ending balance	1,800
Steelmaking
Goodwill [Roll Forward]
Beginning balance	1,765
Foreign currency translation	(14)
Ending balance	1,751
Other Businesses
Goodwill [Roll Forward]
Beginning balance	49
Foreign currency translation	0
Ending balance	$ 49