REVENUES - Revenues By Product Line (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 5,226	$ 4,934	$ 10,148	$ 9,563
Steelmaking
Disaggregation of Revenue [Line Items]
Revenues	5,096	4,808	9,893	9,303
Steelmaking \| Third Party
Disaggregation of Revenue [Line Items]
Revenues	5,052	4,771	9,809	9,238
Steelmaking \| Hot-rolled steel
Disaggregation of Revenue [Line Items]
Revenues	1,539	1,332	2,949	2,498
Steelmaking \| Cold-rolled steel
Disaggregation of Revenue [Line Items]
Revenues	660	645	1,297	1,236
Steelmaking \| Coated steel
Disaggregation of Revenue [Line Items]
Revenues	1,532	1,392	2,963	2,753
Steelmaking \| Stainless and electrical steel
Disaggregation of Revenue [Line Items]
Revenues	525	434	990	878
Steelmaking \| Plate steel
Disaggregation of Revenue [Line Items]
Revenues	253	275	507	522
Steelmaking \| Other steel products
Disaggregation of Revenue [Line Items]
Revenues	16	276	124	523
Steelmaking \| Other
Disaggregation of Revenue [Line Items]
Revenues	527	417	979	828
Other Businesses
Disaggregation of Revenue [Line Items]
Revenues	177	163	344	325
Other Businesses \| Third Party
Disaggregation of Revenue [Line Items]
Revenues	174		339	325
Other Businesses \| Other
Disaggregation of Revenue [Line Items]
Revenues	$ 174	$ 163
Other Businesses \| Other \| Third Party
Disaggregation of Revenue [Line Items]
Revenues			$ 339	$ 325