SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended								12 Months Ended			74 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Sales [Abstract]
Sales	$ 1,385.7	$ 1,452.7	$ 1,364.0	$ 1,348.2	$ 1,267.4	$ 533.6	$ 535.4	$ 518.0	$ 5,550.6	$ 2,854.4	$ 2,241.2
Income before taxes [Abstract]
Net (loss) income									(34.2)	6.7	162.7
Restructuring charge									(112.9)	(2.7)	(15.7)	$ (190.2)
Acquisition-related costs									(48.8)	(123.4)	(4.2)
Other operating income									10.6	45.7	1.5
Interest expense									(191.9)	(97.0)	(43.8)
Interest income									3.4	1.1	1.3
Earnings of non-consolidated affiliates [Abstract]
Earnings of non-consolidated affiliates									1.7	1.7	1.7
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									533.5	228.9	139.1
Capital spending [Abstract]
Total capital spending									278.0	130.9	71.8
Assets
Total assets	8,762.6				9,288.9				8,762.6	9,288.9		8,762.6
Investments-Affiliated Companies (at equity) [Abstract]
Investments in non-consolidated affiliates	26.7				25.0				26.7	25.0		26.7
Chlor Alkali Products and Vinyls Segment
Sales [Abstract]
Sales									2,999.3	1,713.4	1,502.8
Income before taxes [Abstract]
Net (loss) income									224.9	115.5	130.1
Earnings of non-consolidated affiliates [Abstract]
Earnings of non-consolidated affiliates									1.7	1.7	1.7
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									418.1	186.1	119.4
Capital spending [Abstract]
Total capital spending									195.1	94.5	49.6
Assets
Total assets	6,521.4				6,690.7				6,521.4	6,690.7		6,521.4
Investments-Affiliated Companies (at equity) [Abstract]
Investments in non-consolidated affiliates	26.7				25.0				26.7	25.0		26.7
Epoxy Segment
Sales [Abstract]
Sales									1,822.0	429.6	0.0
Income before taxes [Abstract]
Net (loss) income									15.4	(7.5)	0.0
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									90.0	20.9	0.0
Capital spending [Abstract]
Total capital spending									45.4	7.7	0.0
Assets
Total assets	1,514.3				1,591.2				1,514.3	1,591.2		1,514.3
Winchester Segment
Sales [Abstract]
Sales									729.3	711.4	738.4
Income before taxes [Abstract]
Net (loss) income									120.9	115.6	127.3
Restructuring charge									(0.8)	(0.7)	(1.9)	(25.5)
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									18.5	17.4	16.3
Capital spending [Abstract]
Total capital spending									19.5	25.6	21.4
Assets
Total assets	424.0				411.9				424.0	411.9		424.0
Corporate/Other
Income before taxes [Abstract]
Net (loss) income									(55.8)	(40.6)	(33.8)
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									6.9	4.5	3.4
Capital spending [Abstract]
Total capital spending									18.0	3.1	$ 0.8
Assets
Total assets	$ 302.9				$ 595.1				$ 302.9	$ 595.1		$ 302.9