RESTRUCTURING CHARGES (Details 2) - USD ($) $ in Millions	9 Months Ended	10 Months Ended	11 Months Ended	12 Months Ended			25 Months Ended	69 Months Ended
	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2021
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 27.9	$ 9.0	$ 76.5		$ 271.3
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges				0.0	0.0	58.9		137.0
Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges				10.3	2.2	2.1		19.1
Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges				11.6	5.4	14.6		65.2
Employee Relocation Cost
Restructuring Cost and Reserve [Line Items]
Restructuring charges								1.7
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges				6.0	1.4	0.9		48.3
McIntosh Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 5.6		5.6
McIntosh Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges		0.0
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		0.0
McIntosh Plan | Chlor Alkali Products and Vinyls | Employee Relocation Cost
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		$ 5.6
Freeport 2021 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 6.5	6.5
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			6.5
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Employee Relocation Cost
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				3.9	3.8		$ 66.6
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							5.6
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Employee Relocation Cost
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				1.6	$ 5.2	$ 15.8		182.3
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								53.1
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | Employee Relocation Cost
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								$ 42.7
Productivity Plan | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 10.3			$ 10.3
Productivity Plan | Corporate and Other | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0
Productivity Plan | Corporate and Other | Employee severance and related benefit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	10.3
Productivity Plan | Corporate and Other | Facility exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0
Productivity Plan | Corporate and Other | Employee Relocation Cost
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0
Productivity Plan | Corporate and Other | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0.0