SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended								12 Months Ended			86 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Sales [Abstract]
Sales	$ 1,619.9	$ 1,554.9	$ 1,526.5	$ 1,567.1	$ 1,385.7	$ 1,452.7	$ 1,364.0	$ 1,348.2	$ 6,268.4	$ 5,550.6	$ 2,854.4
Income (loss) before taxes [Abstract]
Income (loss) before taxes									(117.2)	34.2	(6.7)
Restructuring charge									(37.6)	(112.9)	(2.7)	$ (187.2)
Acquisition-related costs									(12.8)	(48.8)	(123.4)
Other operating income									3.3	10.6	45.7
Interest expense									(217.4)	(191.9)	(97.0)
Interest income									1.8	3.4	1.1
Earnings of non-consolidated affiliates [Abstract]
Earnings of non-consolidated affiliates									1.8	1.7	1.7
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									558.9	533.5	228.9
Capital spending [Abstract]
Total capital spending									294.3	278.0	130.9
Assets
Total assets	9,218.3				8,762.6				9,218.3	8,762.6		9,218.3
Investments-Affiliated Companies (at equity) [Abstract]
Investments in non-consolidated affiliates	28.5				26.7				28.5	26.7		28.5
Chlor Alkali Products and Vinyls Segment
Sales [Abstract]
Sales									3,500.8	2,999.3	1,713.4
Income (loss) before taxes [Abstract]
Income (loss) before taxes									(405.8)	(224.9)	(115.5)
Earnings of non-consolidated affiliates [Abstract]
Earnings of non-consolidated affiliates									1.8	1.7	1.7
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									432.2	418.1	186.1
Capital spending [Abstract]
Total capital spending									209.5	195.1	94.5
Assets
Total assets	7,008.0				6,521.4				7,008.0	6,521.4		7,008.0
Investments-Affiliated Companies (at equity) [Abstract]
Investments in non-consolidated affiliates	28.5				26.7				28.5	26.7		28.5
Epoxy Segment
Sales [Abstract]
Sales									2,086.4	1,822.0	429.6
Income (loss) before taxes [Abstract]
Income (loss) before taxes									11.8	(15.4)	7.5
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									94.3	90.0	20.9
Capital spending [Abstract]
Total capital spending									37.9	45.4	7.7
Assets
Total assets	1,597.1				1,514.3				1,597.1	1,514.3		1,597.1
Winchester Segment
Sales [Abstract]
Sales									681.2	729.3	711.4
Income (loss) before taxes [Abstract]
Income (loss) before taxes									(72.4)	(120.9)	(115.6)
Restructuring charge										(0.8)	(0.7)	(27.1)
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									19.5	18.5	17.4
Capital spending [Abstract]
Total capital spending									22.5	19.5	25.6
Assets
Total assets	425.2				424.0				425.2	424.0		425.2
Corporate/Other
Income (loss) before taxes [Abstract]
Income (loss) before taxes									86.5	55.8	40.6
Depreciation and amortization expense [Abstract]
Total depreciation and amortization expense									12.9	6.9	4.5
Capital spending [Abstract]
Total capital spending									24.4	18.0	$ 3.1
Assets
Total assets	$ 188.0				$ 302.9				$ 188.0	$ 302.9		$ 188.0