RESTRUCTURING CHARGE (Details 2) - USD ($) $ in Millions	3 Months Ended							9 Months Ended		10 Months Ended	58 Months Ended	59 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0.3	$ 0.7	$ 1.2		$ 1.2	$ 2.3	$ 1.0	$ 2.2	$ 4.5			$ 76.8
Write-off of equipment and facility
Restructuring Cost and Reserve [Line Items]
Restructuring charges												21.3
Employee severance and job related benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	0.0	0.0		0.5	1.2	0.2					21.0
Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.2	0.2	0.2		0.4	0.8	0.7					18.1
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	0.2	0.1		0.3	0.0	0.1					6.0
Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.0	$ 0.0	$ 0.7		0.0	$ 0.0	$ 0.0					5.9
Chlor Alkali Products Becancour
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.1			$ 10.0				1.7		$ 11.7
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										2.3
Chlor Alkali Products Becancour | Facility exit costs (asset retirement obligations)
Restructuring Cost and Reserve [Line Items]
Restructuring charges										0.3
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										0.0
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					0.7				3.0		$ 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	$ 0.2				$ 0.5			$ 0.5	$ 1.5			24.5
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												2.2
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												5.1
Winchester Segment | Lease and other contract termination costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges												$ 0.0