SEGMENT INFORMATION (Details 3) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Sales	$ 1,592.9	$ 1,728.4	$ 3,146.3	$ 3,438.7
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	909.2	1,018.7	1,781.4	1,954.8
Chlor Alkali Products and Vinyls | Caustic soda [Member]
Disaggregation of Revenue [Line Items]
Sales	461.0	564.8	923.1	1,101.7
Chlor Alkali Products and Vinyls | Chlorine, chlorine-derivatives and other co-products [Member]
Disaggregation of Revenue [Line Items]
Sales	448.2	453.9	858.3	853.1
Epoxy
Disaggregation of Revenue [Line Items]
Sales	518.8	543.8	1,042.8	1,147.1
Epoxy | Aromatics and allylics [Member]
Disaggregation of Revenue [Line Items]
Sales	234.8	237.8	478.6	546.2
Epoxy | Epoxy resins [Member]
Disaggregation of Revenue [Line Items]
Sales	284.0	306.0	564.2	600.9
Winchester
Disaggregation of Revenue [Line Items]
Sales	164.9	165.9	322.1	336.8
Winchester | Commercial [Member]
Disaggregation of Revenue [Line Items]
Sales	103.6	105.9	210.0	217.1
Winchester | Military and law enforcement [Member]
Disaggregation of Revenue [Line Items]
Sales	$ 61.3	$ 60.0	$ 112.1	$ 119.7