RESTRUCTURING CHARGE (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		53 Months Ended	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1.2	$ 1.0	$ 75.8
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges			21.0
Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0	0.2	21.0
Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.2	0.7	17.7
Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges			4.5
Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.1	0.1	5.7
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.7	0	5.9
Chlor Alkali Products Becancour
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1.2		11.2	10.0
Chlor Alkali Products Becancour | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges			3.2
Chlor Alkali Products Becancour | Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges			2.3
Chlor Alkali Products Becancour | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges			0.1
Chlor Alkali Products Becancour | Pension and other postretirement benefits curtailment
Restructuring Cost and Reserve [Line Items]
Restructuring charges			0.4
Chlor Alkali Products Becancour | Employee relocation costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			0
Chlor Alkali Products Becancour | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			5.2
Chlor Alkali Products Mercury
Restructuring Cost and Reserve [Line Items]
Restructuring charges		0.6	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
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	0.1	0.4	24.0
Winchester Segment | Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges			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			2.0
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			4.8
Winchester Segment | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges			$ 0