SEGMENT INFORMATION (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Sales	$ 8,910.6	$ 5,758.0	$ 6,110.0
U.S.
Disaggregation of Revenue [Line Items]
Sales	5,268.0	3,536.5	3,599.5
Europe
Disaggregation of Revenue [Line Items]
Sales	1,680.8	800.9	990.4
Other foreign
Disaggregation of Revenue [Line Items]
Sales	1,961.8	1,420.6	1,520.1
Chlor Alkali Products and Vinyls
Disaggregation of Revenue [Line Items]
Sales	4,140.8	2,959.9	3,420.1
Chlor Alkali Products and Vinyls | Caustic soda
Disaggregation of Revenue [Line Items]
Sales	1,869.3	1,408.3	1,737.4
Chlor Alkali Products and Vinyls | Chlorine, chlorine derivatives and other products
Disaggregation of Revenue [Line Items]
Sales	2,271.5	1,551.6	1,682.7
Chlor Alkali Products and Vinyls | U.S.
Disaggregation of Revenue [Line Items]
Sales	2,839.1	2,092.5	2,332.1
Chlor Alkali Products and Vinyls | Europe
Disaggregation of Revenue [Line Items]
Sales	203.5	106.7	134.5
Chlor Alkali Products and Vinyls | Other foreign
Disaggregation of Revenue [Line Items]
Sales	1,098.2	760.7	953.5
Epoxy
Disaggregation of Revenue [Line Items]
Sales	3,186.0	1,870.5	2,024.4
Epoxy | Aromatics and allylics
Disaggregation of Revenue [Line Items]
Sales	1,450.5	821.0	945.3
Epoxy | Epoxy resins
Disaggregation of Revenue [Line Items]
Sales	1,735.5	1,049.5	1,079.1
Epoxy | U.S.
Disaggregation of Revenue [Line Items]
Sales	926.7	578.1	664.0
Epoxy | Europe
Disaggregation of Revenue [Line Items]
Sales	1,457.9	684.9	844.2
Epoxy | Other foreign
Disaggregation of Revenue [Line Items]
Sales	801.4	607.5	516.2
Winchester
Disaggregation of Revenue [Line Items]
Sales	1,583.8	927.6	665.5
Winchester | Commercial
Disaggregation of Revenue [Line Items]
Sales	1,104.1	640.5	441.3
Winchester | Military and law enforcement
Disaggregation of Revenue [Line Items]
Sales	479.7	287.1	224.2
Winchester | U.S.
Disaggregation of Revenue [Line Items]
Sales	1,502.2	865.9	603.4
Winchester | Europe
Disaggregation of Revenue [Line Items]
Sales	19.4	9.3	11.7
Winchester | Other foreign
Disaggregation of Revenue [Line Items]
Sales	$ 62.2	$ 52.4	$ 50.4