SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		54 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020
Sales [Abstract]
Sales	$ 1,437.6			$ 1,576.6			$ 4,103.9	$ 4,722.9
Income (loss) before taxes:
Income (loss) before taxes	(753.4)			43.8			(1,019.4)	72.0
Corporate/Other:
Environmental (expense) income	12.5			(0.8)			17.9	23.0
Restructuring charges	(1.3)	$ (1.7)	$ (1.7)	(4.9)	$ (3.8)	$ (4.0)	(4.7)	(12.7)	$ (245.0)
Goodwill impairment	(699.8)			0.0			(699.8)	0.0
Other operating (expense) income	(0.2)			0.1			(0.1)	0.3
Interest expense	(74.6)			(63.9)			(207.1)	(179.2)
Interest income	0.1			0.2			0.4	0.7
Non-operating pension income	4.9			4.1			14.4	12.2
Other income	0.0			0.0			0.0	11.2
Recoveries for costs incurred and expensed	0.0			0.0			0.0	4.8
Chlor Alkali Products and Vinyls
Sales [Abstract]
Sales	755.1			876.3			2,166.2	2,657.7
Income (loss) before taxes:
Income (loss) before taxes	37.8			112.7			(53.5)	303.8
Corporate/Other:
Goodwill impairment							(557.6)
Epoxy
Sales [Abstract]
Sales	476.1			511.6			1,350.7	1,554.4
Income (loss) before taxes:
Income (loss) before taxes	14.9			24.2			13.6	38.6
Corporate/Other:
Goodwill impairment							(142.2)
Winchester
Sales [Abstract]
Sales	206.4			188.7			587.0	510.8
Income (loss) before taxes:
Income (loss) before taxes	21.0			13.9			47.5	33.1
Corporate/Other
Corporate/Other:
Environmental (expense) income	12.5			(0.8)			17.9	18.2
Other corporate and unallocated costs	(43.7)			(43.4)			(112.2)	(117.8)
Restructuring charges	$ (1.3)			$ (4.9)			$ (4.7)	$ (12.7)