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SUPPLEMENTARY FINANCIAL STATEMENT INFORMATION - Non-cash Investing and Financing Activities (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
Noncash or Part Noncash Acquisitions [Line Items] |  |  |
1.500% 2025 Convertible Senior Notes redemption | $ 0 | $ 0 | $ 25
Stelco Holdings Inc |  |  |
Noncash or Part Noncash Acquisitions [Line Items] |  |  |
Other Significant Noncash Transaction, Value of Consideration Given, Common Shares | $ (343) |  |

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