RESTRUCTURING CHARGES (Details 1) $ in Millions	3 Months Ended				6 Months Ended		7 Months Ended	51 Months Ended
	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 11, 2019 T	Dec. 31, 2018 USD ($)	Mar. 21, 2016 T
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1.7	$ 1.7	$ 3.8	$ 4.0	$ 3.4	$ 7.8		$ 243.7
Inception to date Amounts Utilized (cash)								101.5
Inception to date Amounts Utilized (non-cash)								139.6
Accrued restructuring costs	2.6		6.2		2.6	6.2	$ 2.6	2.6	$ 3.1		$ 8.2
Freeport | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Freeport Chlor Alkali Capacity Reduction | T										230,000
Restructuring charges	0.5				0.5		59.4
Additional restructuring and related expected cost	50.0				50.0		50.0	50.0
Geelong | Winchester
Restructuring Cost and Reserve [Line Items]
Restructuring charges			0.2			0.3
Other Winchester | Winchester
Restructuring Cost and Reserve [Line Items]
Restructuring charges						1.4
Capacity Reductions | Chlor Alkali Products and Vinyls
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.2		$ 3.6		2.9	$ 6.1		178.4
Additional restructuring and related expected cost	$ 3.0				$ 3.0		$ 3.0	$ 3.0
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