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GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES - Amortization of Intangible Liability (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract] |  |
Amortization of Intangible Liabilities | $ (1.0) | $ (2.0)
Remained of 2021 | (6.0) |
2022 | (5.0) |
2023 | (5.0) |
2024 | (5.0) |
2025 | (5.0) |
2026 | $ (5.0) |

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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, Next Twelve Months + 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 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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