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BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Details) - Nov. 01, 2024 - Stelco Holdings Inc | $ / shares shares | $ / shares
--- | --- | ---
Business Acquisition [Line Items] |  |
Price per share (in dollars per share) | (per share) | $ 60.00 | $ 13.27
Shares of Cliffs common shares issued to Stelco Holdings stockholders (in shares) | shares | 25,862,021 |
Stelco Holdings Inc |  |
Business Acquisition [Line Items] |  |
Price per share (in dollars per share) | $ / shares | $ 60.00 |

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