Annual report pursuant to Section 13 and 15(d)

PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details)

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PROPERTY, PLANT AND EQUIPMENT (Narrative) (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Property, Plant and Equipment [Line Items]      
Depreciation $ 78.8 $ 106.8 $ 119.2
Depletion $ 6.8 $ 3.8 $ 7.4