SEGMENT INFORMATION (Details 2) - 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
United States
Disaggregation of Revenue [Line Items]
Sales	751.4	923.2	1,618.2	1,832.6
Europe
Disaggregation of Revenue [Line Items]
Sales	169.5	264.0	396.6	540.8
Other foreign
Disaggregation of Revenue [Line Items]
Sales	320.3	405.7	651.5	772.9
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 | United States
Disaggregation of Revenue [Line Items]
Sales	450.3	601.0	984.2	1,205.0
Chlor Alkali Products and Vinyls | Europe
Disaggregation of Revenue [Line Items]
Sales	26.8	39.1	57.0	77.7
Chlor Alkali Products and Vinyls | Other foreign
Disaggregation of Revenue [Line Items]
Sales	174.1	269.1	369.9	498.7
Epoxy
Disaggregation of Revenue [Line Items]
Sales	397.4	518.8	874.6	1,042.8
Epoxy | United States
Disaggregation of Revenue [Line Items]
Sales	122.5	175.4	281.3	339.5
Epoxy | Europe
Disaggregation of Revenue [Line Items]
Sales	140.4	222.6	334.8	458.0
Epoxy | Other foreign
Disaggregation of Revenue [Line Items]
Sales	134.5	120.8	258.5	245.3
Winchester
Disaggregation of Revenue [Line Items]
Sales	192.6	164.9	380.6	322.1
Winchester | United States
Disaggregation of Revenue [Line Items]
Sales	178.6	146.8	352.7	288.1
Winchester | Europe
Disaggregation of Revenue [Line Items]
Sales	2.3	2.3	4.8	5.1
Winchester | Other foreign
Disaggregation of Revenue [Line Items]
Sales	$ 11.7	$ 15.8	$ 23.1	$ 28.9