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GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Amortization of Intangible Liability (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Goodwill and Intangible Assets Disclosure [Abstract] |  |  |  |
Amortization of Intangible Liabilities | $ (1) | $ (1) | $ (4) | $ (4)
Remainder of 2025 | (1) |  | (1) |
2026 | (5) |  | (5) |
2027 | (5) |  | (5) |
2028 | (5) |  | (5) |
2029 | (5) |  | (5) |
2030 | $ (5) |  | $ (5) |

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- Definition Amortization Of Intangible Liability + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Remainder Of Fiscal Year + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Year Five + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Year Four + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Year One + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Year Three + References No definition available. + Details
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- Definition Finite-Lived Intangible Liabilities, Amortization Credit, Year Two + References No definition available. + Details
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Namespace Prefix: | clf_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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- References No definition available. + Details
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