REVENUES - Revenues By Product Line (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 5,612	$ 4,734	$ 15,760	$ 14,297
Steelmaking
Disaggregation of Revenue [Line Items]
Revenues	5,492	4,585	15,385	13,888
Steelmaking \| Third Party
Disaggregation of Revenue [Line Items]
Revenues	5,447	4,561	15,256	13,799
Steelmaking \| Hot-rolled steel
Disaggregation of Revenue [Line Items]
Revenues	1,749	1,122	4,698	3,620
Steelmaking \| Cold-rolled steel
Disaggregation of Revenue [Line Items]
Revenues	704	636	2,001	1,872
Steelmaking \| Coated steel
Disaggregation of Revenue [Line Items]
Revenues	1,652	1,442	4,615	4,195
Steelmaking \| Stainless and electrical steel
Disaggregation of Revenue [Line Items]
Revenues	514	466	1,504	1,344
Steelmaking \| Plate steel
Disaggregation of Revenue [Line Items]
Revenues	267	286	774	808
Steelmaking \| Other steel products
Disaggregation of Revenue [Line Items]
Revenues	0	204	124	727
Steelmaking \| Other
Disaggregation of Revenue [Line Items]
Revenues	561	405	1,540	1,233
Other Businesses
Disaggregation of Revenue [Line Items]
Revenues	169	173	513	498
Other Businesses \| Third Party
Disaggregation of Revenue [Line Items]
Revenues	165		504	498
Other Businesses \| Other
Disaggregation of Revenue [Line Items]
Revenues	$ 165	$ 173
Other Businesses \| Other \| Third Party
Disaggregation of Revenue [Line Items]
Revenues			$ 504	$ 498