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ACQUISITIONS - Intangible assets and liabilities (Details) - AK Steel [Member] $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Acquired Finite-Lived Intangible Assets [Line Items] |
Finite-lived Intangible Assets Acquired | $ 148.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 17 years
Finite-lived Intangible Liability Assumed | $ (71.0)
Assumed Finite-lived Intangible Liabilities, Weighted Average Useful Life | 12 years
Customer Relationships |
Acquired Finite-Lived Intangible Assets [Line Items] |
Finite-lived Intangible Assets Acquired | $ 77.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 18 years
Technology-Based Intangible Assets |
Acquired Finite-Lived Intangible Assets [Line Items] |
Finite-lived Intangible Assets Acquired | $ 60.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 17 years
Trademarks and Trade Names |
Acquired Finite-Lived Intangible Assets [Line Items] |
Finite-lived Intangible Assets Acquired | $ 11.0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 10 years

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