SEGMENT INFORMATION (Details 2) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Sales	$ 2,221.3	$ 1,241.2	$ 4,140.1	$ 2,666.3
United States
Disaggregation of Revenue [Line Items]
Sales	1,340.8	751.4	2,441.1	1,618.2
Europe
Disaggregation of Revenue [Line Items]
Sales	449.5	169.5	802.8	396.6
Other foreign
Disaggregation of Revenue [Line Items]
Sales	431.0	320.3	896.2	651.5
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	967.3	651.2	1,834.3	1,411.1
Chlor Alkali Products and Vinyls | United States
Disaggregation of Revenue [Line Items]
Sales	713.6	450.3	1,290.6	984.2
Chlor Alkali Products and Vinyls | Europe
Disaggregation of Revenue [Line Items]
Sales	39.4	26.8	68.9	57.0
Chlor Alkali Products and Vinyls | Other foreign
Disaggregation of Revenue [Line Items]
Sales	214.3	174.1	474.8	369.9
Epoxy
Disaggregation of Revenue [Line Items]
Sales	850.0	397.4	1,512.6	874.6
Epoxy | United States
Disaggregation of Revenue [Line Items]
Sales	253.6	122.5	411.9	281.3
Epoxy | Europe
Disaggregation of Revenue [Line Items]
Sales	403.8	140.4	723.8	334.8
Epoxy | Other foreign
Disaggregation of Revenue [Line Items]
Sales	192.6	134.5	376.9	258.5
Winchester
Disaggregation of Revenue [Line Items]
Sales	404.0	192.6	793.2	380.6
Winchester | United States
Disaggregation of Revenue [Line Items]
Sales	373.6	178.6	738.6	352.7
Winchester | Europe
Disaggregation of Revenue [Line Items]
Sales	6.3	2.3	10.1	4.8
Winchester | Other foreign
Disaggregation of Revenue [Line Items]
Sales	$ 24.1	$ 11.7	$ 44.5	$ 23.1