SEGMENT REPORTING - Summary of Assets by Segment (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 20,836	$ 20,947
Steelmaking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	20,200	20,327
Other Businesses [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 636	$ 620