RESTRUCTURING CHARGES (Details Textuals) $ in Millions	3 Months Ended						6 Months Ended	9 Months Ended		22 Months Ended	71 Months Ended
	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Mar. 21, 2016 T	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 12, 2014 T	Dec. 31, 2011 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 5.2	$ 8.2	$ 92.8	$ 0.3	$ 0.7	$ 1.2		$ 106.2	$ 2.2		$ 142.9
Inception to date Amounts Utilized (cash)											45.7
Inception to date Amounts Utilized (non-cash)											84.6
Accrued restructuring costs	11.9			7.7			$ 11.9	11.9	7.7	$ 11.9	11.9		$ 6.7	$ 15.7
Chlor Alkali Products and Vinyls Capacity Reductions
Restructuring Cost and Reserve [Line Items]
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
Restructuring charges	4.9						105.0	105.0
Additional restructuring and related expected cost	45.0						45.0	45.0		45.0	45.0
Chlor Alkali Products Becancour
Restructuring Cost and Reserve [Line Items]
Restructuring charges				0.1				0.4	1.7	12.4
Additional restructuring and related expected cost	4.0						4.0	4.0		4.0	4.0
Tonnage reduction in chlor alkali manufacutring capactiy (in tons) | T															185,000
Winchester Segment
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.3			$ 0.2				0.8	$ 0.5		25.5
Additional restructuring and related expected cost	0.5						0.5	0.5		0.5	0.5
Estimated Project Cost For Plant Relocation	110.0						110.0	110.0		110.0	110.0
Estimated Capital Spending For Facility Relocation	$ 80.0						$ 80.0	80.0		$ 80.0	$ 80.0
Government Grants for Facility Relocation Capital Spending																$ 31.0
Winchester Segment | Minimum
Restructuring Cost and Reserve [Line Items]
Forecast to reduce Winchester's annual operating costs								35.0
Winchester Segment | Maximum
Restructuring Cost and Reserve [Line Items]
Forecast to reduce Winchester's annual operating costs								$ 40.0