GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Goodwill (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Goodwill [Line Items]
Goodwill	$ 1,005	$ 1,005
Steelmaking
Goodwill [Line Items]
Goodwill	956	956
Other Businesses
Goodwill [Line Items]
Goodwill	$ 49	$ 49