SEGMENT REPORTING - Segment Assets (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total assets	$ 16,928	$ 17,537
Corporate
Segment Reporting Information [Line Items]
Total assets	406	507
Operating Segments
Segment Reporting Information [Line Items]
Total assets	16,522	17,030
Operating Segments | Steelmaking
Segment Reporting Information [Line Items]
Total assets	16,362	16,880
Operating Segments | Other Businesses
Segment Reporting Information [Line Items]
Total assets	666	657
Eliminations
Segment Reporting Information [Line Items]
Total assets	$ (506)	$ (507)