RESTRUCTURING CHARGES (Details 3) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		64 Months Ended
RESTRUCTURING CHARGES (Details 3) - USD ($) $ in Millions	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 10.5	$ 9.1	$ 7.4	$ 4.0	$ 19.6	$ 11.4	$ 279.5
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.6	0.8	0.0	0.0			86.5
Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	4.1	3.8	1.6			36.2
Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	8.9	4.1	3.6	2.2			111.6
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	$ 0.1	0.0	$ 0.2			45.2
Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0		0.0		0.0	0.0	151.0
Chlor Alkali Products and Vinyls \| Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges							61.6
Chlor Alkali Products and Vinyls \| Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							12.5
Chlor Alkali Products and Vinyls \| Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							70.0
Chlor Alkali Products and Vinyls \| Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							6.9
Epoxy
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0		0.0		0.0	0.0	125.4
Epoxy \| Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges							24.9
Epoxy \| Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							20.6
Epoxy \| Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							41.6
Epoxy \| Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							38.3
Winchester
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0.0		$ 0.0		$ 0.0	$ 0.0
Other
Restructuring Cost and Reserve [Line Items]
Restructuring charges							3.1
Other \| Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.0
Other \| Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							3.1
Other \| Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.0
Other \| Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							$ 0.0