GOODWILL AND INTANGIBLE ASSETS AND LIABILITIES (Intangible Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
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