SEGMENT INFORMATION (Details 3) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Sales	$ 1,918.8	$ 1,425.1
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	867.0	759.9
Chlor Alkali Products and Vinyls | Caustic soda
Disaggregation of Revenue [Line Items]
Sales	347.0	360.2
Chlor Alkali Products and Vinyls | Chlorine, chlorine-derivatives and other co-products
Disaggregation of Revenue [Line Items]
Sales	520.0	399.7
Epoxy
Disaggregation of Revenue [Line Items]
Sales	662.6	477.2
Epoxy | Aromatics and allylics
Disaggregation of Revenue [Line Items]
Sales	312.0	217.4
Epoxy | Epoxy resins
Disaggregation of Revenue [Line Items]
Sales	350.6	259.8
Winchester
Disaggregation of Revenue [Line Items]
Sales	389.2	188.0
Winchester | Commercial
Disaggregation of Revenue [Line Items]
Sales	261.0	127.1
Winchester | Military and law enforcement
Disaggregation of Revenue [Line Items]
Sales	$ 128.2	$ 60.9