GOODWILL AND INTANGIBLES (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill	$ 2,120.0	$ 2,118.0	$ 2,174.1
Goodwill, Purchase Accounting Adjustments		(55.0)
Foreign currency translation adjustment	2.0	(1.1)
Chlor Alkali Products and Vinyls Segment
Goodwill [Line Items]
Goodwill	1,832.9	1,831.3	1,877.5
Goodwill, Purchase Accounting Adjustments		(45.3)
Foreign currency translation adjustment	1.6	(0.9)
Epoxy Segment
Goodwill [Line Items]
Goodwill	287.1	286.7	$ 296.6
Goodwill, Purchase Accounting Adjustments		(9.7)
Foreign currency translation adjustment	$ 0.4	$ (0.2)