SEGMENT INFORMATION (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Sales by Product Line
Total net sales	$ 1,068.7	$ 1,269.4	$ 1,236.9	$ 993.7	$ 1,134.5	$ 1,197.5	$ 1,272.8	$ 1,061.2	$ 4,568.7	$ 4,666.0	$ 3,325.8
Chlorovinyls
Sales by Product Line
Total net sales									2,930.2	2,917.3	1,344.9
Chlorovinyls | Chlor-alkali and derivative products
Sales by Product Line
Total net sales									2,435.3	2,447.2	886.2
Chlorovinyls | Compound products
Sales by Product Line
Total net sales									494.9	470.1	458.7
Building Products
Sales by Product Line
Total net sales									878.6	849.9	876.6
Building Products | Window and door profiles
Sales by Product Line
Total net sales									314.5	314.4	319.1
Building Products | Outdoor building products
Sales by Product Line
Total net sales									564.1	535.5	557.5
Aromatics
Sales by Product Line
Total net sales									759.9	898.8	1,104.3
Aromatics | Cumene products
Sales by Product Line
Total net sales									499.2	569.8	763.5
Aromatics | Phenol and acetone products
Sales by Product Line
Total net sales									$ 260.7	$ 329.0	$ 340.8