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GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES (Intangible Assets and Liabilities) (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019
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Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | $ 235.2 |
Finite-Lived Intangible Assets, Accumulated Amortization | (25.2) |
Finite-Lived Intangible Assets, Net | 210.0 |
Finite-Lived Intangible Liability, Gross | (140.0) |
Finite-Lived Intangible Liability, Accumulated Amortization | 2.1 |
Finite-Lived Intangible Liability, Net | (137.9) |
Customer Relationships [Member] |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 91.0 |
Finite-Lived Intangible Assets, Accumulated Amortization | (0.5) |
Finite-Lived Intangible Assets, Net | 90.5 |
Technology-Based Intangible Assets [Member] |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 61.0 |
Finite-Lived Intangible Assets, Accumulated Amortization | (0.3) |
Finite-Lived Intangible Assets, Net | 60.7 |
Trademarks and Trade Names [Member] |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 11.0 |
Finite-Lived Intangible Assets, Accumulated Amortization | (0.1) |
Finite-Lived Intangible Assets, Net | 10.9 |
Mining Permits [Member] |  |
Finite-Lived Intangible Assets [Line Items] |  |
Finite-Lived Intangible Assets, Gross | 72.2 | $ 72.2
Finite-Lived Intangible Assets, Accumulated Amortization | (24.3) | (24.1)
Finite-Lived Intangible Assets, Net | $ 47.9 | $ 48.1

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- Definition Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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