RESTRUCTURING CHARGES (Details 3) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended | 13 Months Ended | 14 Months Ended | 28 Months Ended | 72 Months Ended |
Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2022 | Mar. 31, 2022 | Mar. 31, 2022 | Mar. 31, 2022 | Mar. 31, 2022 |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | $ 3.1 | $ 6.9 | | | | | $ 274.4 |
Write-off of equipment and facility | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 0.4 | 0 | | | | | 137 |
Employee severance and related benefit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 0 | 0 | | | | | 19.1 |
Facility exit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 2.6 | 2.3 | | | | | 67.8 |
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 | 0.1 | 4.6 | | | | | 48.8 |
McIntosh Plan | Chlor Alkali Products and Vinyls | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 0.9 | 4.4 | | $ 6.5 | | | |
McIntosh Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | 0 | | | |
McIntosh Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | 0 | | | |
McIntosh Plan | Chlor Alkali Products and Vinyls | Facility exit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | 0.5 | | | |
McIntosh Plan | Chlor Alkali Products and Vinyls | Employee relocation costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | 0 | | | |
McIntosh Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | $ 6 | | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 0.3 | 1.3 | | | $ 6.8 | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Write-off of equipment and facility | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | 0 | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Employee severance and related benefit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | 0 | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Facility exit costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | 6.8 | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Employee relocation costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | 0 | | |
Freeport 2021 Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | $ 0 | | |
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | 1.7 | 0.8 | | | | $ 68.3 | |
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 | | | | | | 7.3 | |
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Employee relocation costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | | 0 | |
Freeport 2019 Plan | Chlor Alkali Products and Vinyls | Lease and other contract termination costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | | | | $ 0 | |
Chlor Alkali 2016 Plan | Chlor Alkali Products and Vinyls | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | $ 0.2 | $ 0.4 | | | | | 182.5 |
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 | | | | | | | $ 42.8 |
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 | | | | |
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 | | | | |
Productivity Plan | Corporate/other | Employee relocation costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | 0 | | | | |
Productivity Plan | Corporate/other | Lease and other contract termination costs | | | | | | | |
Restructuring Cost and Reserve [Line Items] | | | | | | | |
Restructuring charges | | | $ 0 | | | | |