SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		66 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Sales [Abstract]
Sales	$ 2,340.1			$ 1,437.6			$ 6,480.2	$ 4,103.9
Income (loss) before taxes:
Income (loss) before taxes	504.3			(753.4)			1,147.7	(1,019.4)
Corporate/Other:
Environmental expense	3.6			12.5			10.8	17.9
Restructuring charges	(3.6)	$ (14.0)	$ (6.9)	(1.3)	$ (1.7)	$ (1.7)	(24.5)	(4.7)	$ (267.9)
Goodwill impairment	0.0			(699.8)			0.0	(699.8)
Other operating expense	(0.5)			(0.2)			0.0	(0.1)
Interest expense	(54.0)			(74.6)			(204.4)	(207.1)
Interest income	0.1			0.1			0.2	0.4
Non-operating pension income	9.2			4.9			26.7	14.4
Corporate/other
Corporate/Other:
Environmental expense	3.6			12.5			8.6	17.9
Other corporate and unallocated costs	(36.8)			(43.7)			(100.7)	(112.2)
Restructuring charges	(3.6)			(1.3)			(24.5)	(4.7)
Chlor Alkali Products and Vinyls
Sales [Abstract]
Sales	1,062.4			755.1			2,896.7	2,166.2
Income (loss) before taxes:
Income (loss) before taxes	263.0			37.8			703.0	(53.5)
Corporate/Other:
Goodwill impairment				(557.6)				(557.6)
Epoxy
Sales [Abstract]
Sales	877.7			476.1			2,390.3	1,350.7
Income (loss) before taxes:
Income (loss) before taxes	215.2			14.9			445.7	13.6
Corporate/Other:
Goodwill impairment				(142.2)				(142.2)
Winchester
Sales [Abstract]
Sales	400.0			206.4			1,193.2	587.0
Income (loss) before taxes:
Income (loss) before taxes	$ 115.3			$ 21.0			$ 310.3	$ 47.5