GOODWILL AND INTANGIBLES (Details 1) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill	$ 2,119.7	$ 2,119.5	$ 2,120.0	$ 2,118.0
Foreign currency translation adjustment	(0.3)	1.5
Chlor Alkali Products and Vinyls Segment
Goodwill [Line Items]
Goodwill	1,832.7	1,832.5	1,832.9	1,831.3
Foreign currency translation adjustment	(0.2)	1.2
Epoxy Segment
Goodwill [Line Items]
Goodwill	287.0	287.0	$ 287.1	$ 286.7
Foreign currency translation adjustment	$ (0.1)	$ 0.3