SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		55 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019
Sales [Abstract]
Sales	$ 1,592.9		$ 1,728.4		$ 3,146.3	$ 3,438.7
Income (loss) before taxes:
Income (loss) before taxes	(24.9)		74.3		28.2	101.8
Corporate/Other:
Environmental expense	22.0		4.4		23.8	6.7
Restructuring charges	(3.8)	$ (4.0)	(6.4)	$ (4.0)	(7.8)	(10.4)	$ (189.8)
Acquisition-related costs	0.0		(0.3)		0.0	(0.6)
Other operating income	0.1		0.0		0.2	8.1
Interest expense	(57.9)		(61.1)		(115.3)	(124.8)
Interest income	0.3		0.4		0.5	0.8
Non-operating pension income	4.2		5.4		8.1	10.8
Other income	0.0		0.0		11.2	0.0
Losses of non-consolidated affiliates	0.0		(21.1)		0.0	(20.6)
Gain in Other Operating (Expense) Income due to Insurance Recoveries					8.0
Recoveries for costs incurred and expensed	(4.8)		0.0		(4.8)	0.0
Chlor Alkali Products and Vinyls
Sales [Abstract]
Sales	909.2		1,018.7		1,781.4	1,954.8
Income (loss) before taxes:
Income (loss) before taxes	70.7		149.4		191.1	279.9
Epoxy
Sales [Abstract]
Sales	518.8		543.8		1,042.8	1,147.1
Income (loss) before taxes:
Income (loss) before taxes	3.9		24.8		14.4	2.7
Winchester
Sales [Abstract]
Sales	164.9		165.9		322.1	336.8
Income (loss) before taxes:
Income (loss) before taxes	10.1		11.8		19.2	23.8
Corporate/Other
Corporate/Other:
Environmental expense	17.2		4.4		19.0	6.7
Other corporate and unallocated costs	(35.3)		(45.3)		(74.4)	(81.8)
Restructuring charges	(3.8)		(6.4)		(7.8)	(10.4)
Acquisition-related costs	$ 0.0		(0.3)		$ 0.0	(0.6)
Bay Gas
Corporate/Other:
Bay Gas non-cash impairment charge			$ 21.5			$ 21.5