SEGMENT REPORTING - Summary of Assets by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 20,290	$ 20,947
Steelmaking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	19,663	20,327
Other Businesses [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 627	$ 620