RESTRUCTURING CHARGES (Details) $ in Millions	9 Months Ended	10 Months Ended	11 Months Ended	12 Months Ended			25 Months Ended	69 Months Ended
	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2021 USD ($)	Oct. 21, 2021 T	May 18, 2021 T	Mar. 15, 2021 T	Dec. 11, 2019 T	Dec. 31, 2018 USD ($)	Mar. 21, 2016 T
Restructuring Cost and Reserve [Line Items]
Restructuring charges				$ 27.9	$ 9.0	$ 76.5		$ 271.3
Restructuring and Related Cost, Incurred Cost								120.9
Restructuring Reserve, Settled without Cash								138.1
Accrued Restructuring Costs	$ 12.3	$ 12.3	$ 12.3	12.3	3.5	3.1	$ 12.3	12.3					$ 8.2
Productivity Plan | Corporate and Other
Restructuring Cost and Reserve [Line Items]
Restructuring charges	10.3			10.3
Additional restructuring and related expected cost	0.0	0.0	0.0	0.0			0.0	0.0
Plaquemine Restructuring Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Additional restructuring and related expected cost	0.0	0.0	0.0	0.0			0.0	0.0
Plaquemine Restructuring Capacity Reduction Percent										20.00%
Plaquemine Restructuring Capacity Reduction | T										225,000
McIntosh Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges		5.6		5.6
Additional restructuring and related expected cost	35.0	35.0	35.0	35.0			35.0	35.0
McIntosh Restructuring Capacity Reduction Percent									50.00%		50.00%
McIntosh Restructuring Capacity Reduction | T									200,000		200,000
Freeport 2021 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges			6.5	6.5
Additional restructuring and related expected cost	20.0	20.0	20.0	20.0			20.0	20.0
Freeport 2019 Plan | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges				3.9	3.8		66.6
Additional restructuring and related expected cost	40.0	40.0	40.0	40.0			40.0	40.0
Freeport Chlor Alkali Capacity Reduction | T												230,000
Geelong | Winchester
Restructuring Cost and Reserve [Line Items]
Restructuring charges					0.4	1.4
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
Additional restructuring and related expected cost	$ 1.0	$ 1.0	$ 1.0	$ 1.0			$ 1.0	$ 1.0
Total Product Segment Production Capacity Decrease | T														433,000
Henderson Product Segment Production Capacity Decrease | T														153,000
Niagara Product Segment Production Capacity | T														300,000
Reduced Niagara Segment Production Capacity | T														240,000
Freeport Product Segment Production Capacity Decrease | T														220,000