RESTRUCTURING CHARGE (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			9 Months Ended		3 Months Ended			9 Months Ended		9 Months Ended		3 Months Ended	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010	Sep. 30, 2011 Employee severance and job related benefits [Member]	Dec. 31, 2010 Employee severance and job related benefits [Member]	Dec. 31, 2010 Employee severance and job related benefits [Member] Chlor Alkali Products Segment [Member]	Dec. 31, 2010 Employee severance and job related benefits [Member] Winchester Segment [Member]	Dec. 31, 2010 Write-off of equipment and facility costs [Member] Chlor Alkali Products Segment [Member]	Sep. 30, 2011 Facility Exit Costs (asset retirement obligations [Member]	Dec. 31, 2010 Facility Exit Costs (asset retirement obligations [Member]	Sep. 30, 2011 Lease and other contract termination costs [Member]	Dec. 31, 2010 Lease and other contract termination costs [Member]	Dec. 31, 2010 Lease and other contract termination costs [Member] Chlor Alkali Products Segment [Member]	Sep. 30, 2011 Pension and other postretirement benefits curtailment [Member]	Dec. 31, 2010 Pension and other postretirement benefits curtailment [Member]	Dec. 31, 2010 Pension and other postretirement benefits curtailment [Member] Winchester Segment [Member]	Dec. 31, 2010 Accelerated Asset Retirement Obligations [Member] Chlor Alkali Products Segment [Member]	Sep. 30, 2011 Employee Relocation Cost [Member]	Dec. 31, 2010 Employee Relocation Cost [Member]	Sep. 30, 2011 Chlor Alkali Products Segment [Member]	Dec. 31, 2010 Chlor Alkali Products Segment [Member]	Sep. 30, 2011 Chlor Alkali Products Segment [Member]	Sep. 30, 2011 Winchester Segment [Member]	Dec. 31, 2010 Winchester Segment [Member]	Sep. 30, 2011 Winchester Segment [Member]
RESTRUCTURING CHARGE [Abstract]
Previous mercury cell capacity tonnage at Charleston, TN facility (in tons)	260,000		260,000
Membrane capacity tonnage capability at Charleston, TN facility (in tons)	200,000		200,000
Estimated capital cost converting Charleston, TN facility	$ 160.0		$ 160.0
Tonnage reduction in chlor alkali manufacturing capacity (in tons)	100,000		100,000
Percentage reduction of electricity usage per ECU produced (in hundredths)	25.00%		25.00%
Percentage of capital spending offset provided by State of Mississippi tax incentives (in hundredths)	40.00%		40.00%
Estimated five-year project cost for Winchester relocation	110.0		110.0
Estimated capital spending for Winchester relocation	80.0		80.0
Forecast annual reduction of Winchester's annual operating costs			30.0
Restructuring charge	4.1	0	6.6	0		3.7		2.8	3.2	17.5	0.5		0		1.0	1.1		3.0	6.7	1.3		2.0	28.0	2.3	2.1	6.2	4.3
Amounts Utilized			(3.3)			(0.2)					(0.5)		(0.2)			(1.1)				(1.3)
Accrued restructuring costs	10.3		10.3		7.0	9.5	6.0				0	0	0.8	1.0		0	0			0	0
Restructuring And Related Cost Expected Cost																								8.0			18.0
Cash Expenditures Incurred			$ 2.2
Term of Winchester East Alton, IL union labor agreement (in years)	5.5		5.5