RESTRUCTURING CHARGES (Details 3) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		30 Months Ended	31 Months Ended	32 Months Ended	46 Months Ended	90 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 11.9	$ 19.2	$ 60.9	$ 7.6	$ 3.6	$ 3.1	$ 92.0	$ 14.3					$ 388.6
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	4.9	12.8	2.7	0.3	0.4							158.0
Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2.6	3.3	0.0	0.0	0.0	0.0							32.4
Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	7.3	9.3	8.4	4.9	3.1	2.6							103.7
Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													1.7
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2.0	$ 1.7	$ 39.7	0.0	$ 0.2	$ 0.1							92.8
McIntosh Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.7			5.5			4.6	7.1		$ 18.5
McIntosh Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges										2.7
McIntosh Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges										0.0
McIntosh Plan | Chlor Alkali Products and Vinyls | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges										9.4
McIntosh Plan | Chlor Alkali Products and Vinyls | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges										0.0
McIntosh Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges										$ 6.4
Freeport 2021 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.7			0.4			2.8	1.9			$ 11.9
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges											0.0
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges											0.0
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges											11.9
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges											0.0
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges											$ 0.0
Freeport 2019 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.9			$ 1.7			4.9	4.9				$ 77.5
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges												58.9
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges												2.1
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges												16.5
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges												0.0
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges												$ 0.0
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges								$ 0.4					182.7
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges													78.1
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													6.7
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													53.2
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													1.7
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													43.0
Epoxy Optimization Plan | Epoxy
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 8.6						$ 79.7						87.7
Epoxy Optimization Plan | Epoxy | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges													18.3
Epoxy Optimization Plan | Epoxy | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													13.3
Epoxy Optimization Plan | Epoxy | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													12.7
Epoxy Optimization Plan | Epoxy | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													0.0
Epoxy Optimization Plan | Epoxy | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges													$ 43.4
Productivity Plan | Corporate/other
Restructuring Cost and Reserve [Line Items]
Restructuring charges									$ 10.3
Productivity Plan | Corporate/other | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges									0.0
Productivity Plan | Corporate/other | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges									10.3
Productivity Plan | Corporate/other | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges									0.0
Productivity Plan | Corporate/other | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges									0.0
Productivity Plan | Corporate/other | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges									$ 0.0