SEGMENT INFORMATION (Details 3) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 1,241.2	$ 1,592.9	$ 2,666.3	$ 3,146.3
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	651.2	909.2	1,411.1	1,781.4
Chlor Alkali Products and Vinyls | Caustic soda
Disaggregation of Revenue [Line Items]
Sales	320.2	461.0	680.4	923.1
Chlor Alkali Products and Vinyls | Chlorine, chlorine-derivatives and other co-products
Disaggregation of Revenue [Line Items]
Sales	331.0	448.2	730.7	858.3
Epoxy
Disaggregation of Revenue [Line Items]
Sales	397.4	518.8	874.6	1,042.8
Epoxy | Aromatics and allylics
Disaggregation of Revenue [Line Items]
Sales	167.0	234.8	384.4	478.6
Epoxy | Epoxy resins
Disaggregation of Revenue [Line Items]
Sales	230.4	284.0	490.2	564.2
Winchester
Disaggregation of Revenue [Line Items]
Sales	192.6	164.9	380.6	322.1
Winchester | Commercial
Disaggregation of Revenue [Line Items]
Sales	135.6	103.6	262.7	210.0
Winchester | Military and law enforcement
Disaggregation of Revenue [Line Items]
Sales	$ 57.0	$ 61.3	$ 117.9	$ 112.1