SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Non-cash Investing and Financing Activities (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Stelco Holdings Inc
Noncash or Part Noncash Acquisitions [Line Items]
Other Significant Noncash Transaction, Value of Consideration Given, Common Shares	$ 0	$ (343)	$ 0

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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