RESTRUCTURING CHARGES (Details 2) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended			25 Months Ended	74 Months Ended
	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2016
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 112.9	$ 2.7	$ 15.7		$ 190.2
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges			76.6	0.5	3.3		97.9
Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges			5.1	0.0	4.5		26.5
Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges			15.5	0.9	2.9		33.9
Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges							4.1
Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			2.1	0.6	0.5		8.3
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			13.6	0.7	4.5		19.5
Chlor Alkali Products Becancour
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 10.0		0.8	2.0		$ 12.8
Chlor Alkali Products Becancour | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges						3.5
Chlor Alkali Products Becancour | Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges						2.7
Chlor Alkali Products Becancour | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges						1.3
Chlor Alkali Products Becancour | Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges						0.0
Chlor Alkali Products Becancour | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges						0.0
Chlor Alkali Products Becancour | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges						$ 5.3
Chlor Alkali Products and Vinyls Capacity Reductions
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 111.3	111.3
Chlor Alkali Products and Vinyls Capacity Reductions | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges		76.6
Chlor Alkali Products and Vinyls Capacity Reductions | Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges		5.1
Chlor Alkali Products and Vinyls Capacity Reductions | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges		14.7
Chlor Alkali Products and Vinyls Capacity Reductions | Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges		0.0
Chlor Alkali Products and Vinyls Capacity Reductions | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		1.4
Chlor Alkali Products and Vinyls Capacity Reductions | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges		$ 13.5
Chlor Alkali Products Mercury
Restructuring Cost and Reserve [Line Items]
Restructuring charges					3.8		40.6
Chlor Alkali Products Mercury | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges							17.8
Chlor Alkali Products Mercury | Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges							5.6
Chlor Alkali Products Mercury | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges							15.6
Chlor Alkali Products Mercury | Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.0
Chlor Alkali Products Mercury | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.9
Chlor Alkali Products Mercury | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.7
Winchester Segment
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 0.8	$ 0.7	$ 1.9		25.5
Winchester Segment | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges							0.0
Winchester Segment | Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges							13.1
Winchester Segment | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges							2.3
Winchester Segment | Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges							4.1
Winchester Segment | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							6.0
Winchester Segment | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges							$ 0.0