GOODWILL AND INTANGIBLE ASSETS (Details 1) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 1,420.2	$ 2,119.7	$ 2,119.6
Goodwill, Impairment Loss	(699.8)	0.0	0.0
Foreign currency translation adjustment	0.3	0.1
Chlor Alkali Products and Vinyls
Goodwill [Line Items]
Goodwill	1,275.3	1,832.7	1,832.6
Goodwill, Impairment Loss	(557.6)
Foreign currency translation adjustment	0.2	0.1
Epoxy
Goodwill [Line Items]
Goodwill	144.9	287.0	$ 287.0
Goodwill, Impairment Loss	(142.2)
Foreign currency translation adjustment	$ 0.1	$ 0.0