SEGMENT INFORMATION (Details 3) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 1,553.4	$ 1,710.3
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	872.2	936.1
Chlor Alkali Products and Vinyls | Caustic soda [Member]
Disaggregation of Revenue [Line Items]
Sales	462.1	536.9
Chlor Alkali Products and Vinyls | Chlorine, chlorine-derivatives and other co-products [Member]
Disaggregation of Revenue [Line Items]
Sales	410.1	399.2
Epoxy
Disaggregation of Revenue [Line Items]
Sales	524.0	603.3
Epoxy | Aromatics and allylics [Member]
Disaggregation of Revenue [Line Items]
Sales	243.8	308.4
Epoxy | Epoxy resins [Member]
Disaggregation of Revenue [Line Items]
Sales	280.2	294.9
Winchester
Disaggregation of Revenue [Line Items]
Sales	157.2	170.9
Winchester | Commercial [Member]
Disaggregation of Revenue [Line Items]
Sales	106.4	111.2
Winchester | Military and law enforcement [Member]
Disaggregation of Revenue [Line Items]
Sales	$ 50.8	$ 59.7