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GOODWILL AND INTANGIBLES (Details 1) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Goodwill	$ 1,420.1	$ 2,119.1	$ 1,420.1	$ 2,119.1	$ 2,119.7	$ 2,119.6
Goodwill impairment	(699.8)	0.0	(699.8)	0.0
Foreign currency translation adjustment			0.2	(0.5)
Chlor Alkali Products and Vinyls
Goodwill [Line Items]
Goodwill	1,275.3	1,832.2	1,275.3	1,832.2	1,832.7	1,832.6
Goodwill impairment			(557.6)
Foreign currency translation adjustment			0.2	(0.4)
Epoxy
Goodwill [Line Items]
Goodwill	$ 144.8	$ 286.9	144.8	286.9	$ 287.0	$ 287.0
Goodwill impairment			(142.2)
Foreign currency translation adjustment			$ 0.0	$ (0.1)