SEGMENT INFORMATION (Details 2) - 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
United States
Disaggregation of Revenue [Line Items]
Sales	923.2	1,011.6	1,832.6	1,958.7
Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	264.0	249.7	540.8	575.0
Other foreign [Member]
Disaggregation of Revenue [Line Items]
Sales	405.7	467.1	772.9	905.0
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 | United States
Disaggregation of Revenue [Line Items]
Sales	601.0	665.1	1,205.0	1,273.2
Chlor Alkali Products and Vinyls | Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	39.1	50.3	77.7	96.1
Chlor Alkali Products and Vinyls | Other foreign [Member]
Disaggregation of Revenue [Line Items]
Sales	269.1	303.3	498.7	585.5
Epoxy
Disaggregation of Revenue [Line Items]
Sales	518.8	543.8	1,042.8	1,147.1
Epoxy | United States
Disaggregation of Revenue [Line Items]
Sales	175.4	200.4	339.5	380.8
Epoxy | Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	222.6	195.2	458.0	473.7
Epoxy | Other foreign [Member]
Disaggregation of Revenue [Line Items]
Sales	120.8	148.2	245.3	292.6
Winchester
Disaggregation of Revenue [Line Items]
Sales	164.9	165.9	322.1	336.8
Winchester | United States
Disaggregation of Revenue [Line Items]
Sales	146.8	146.1	288.1	304.7
Winchester | Europe [Member]
Disaggregation of Revenue [Line Items]
Sales	2.3	4.2	5.1	5.2
Winchester | Other foreign [Member]
Disaggregation of Revenue [Line Items]
Sales	$ 15.8	$ 15.6	$ 28.9	$ 26.9