SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Inventory (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Disclosure Text Block [Abstract]
Finished and semi-finished goods	$ 2,401	$ 2,393
Raw materials	1,848	2,208
Total product inventories	4,249	4,601
Manufacturing supplies and critical spares	523	493
Inventories	4,772	5,094
Excess of current cost over LIFO cost of iron ore inventories	158	142
Effect of inventory build	$ (57)	$ 64