RESTRUCTURING CHARGE (Details Textuals) $ in Millions	3 Months Ended							9 Months Ended		10 Months Ended	58 Months Ended	59 Months Ended
	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 12, 2014 T	Dec. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)	Dec. 09, 2010 T
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
Inception to date Amounts Utilized (cash)												35.9
Inception to date Amounts Utilized (non-cash)												32.5
Accrued restructuring costs	7.7			$ 15.7	10.2			7.7	10.2	$ 7.7	$ 7.7	7.7		$ 10.2
Chlor Alkali Products Becancour
Restructuring Cost and Reserve [Line Items]
Tonnage reduction in chlor alkali manufacutring capactiy (in tons) | T													185,000
Restructuring charges	0.1			$ 10.0				1.7		11.7
Additional restructuring and related expected cost	4.0							4.0		4.0	4.0	4.0
Chlor Alkali Products Mercury
Restructuring Cost and Reserve [Line Items]
Restructuring charges					0.7				3.0		40.6
Previous mercury cell capacity tonnage at Charleston, TN facility (in tons) | T																260,000
Membrane capacity tonnage capability at Charleston, TN facility (in tons) | T																200,000
Winchester Segment
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0.2				$ 0.5			0.5	$ 1.5			24.5
Additional restructuring and related expected cost	1.0							1.0		1.0	1.0	1.0
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