SEGMENT INFORMATION (Details 1) - USD ($) $ in Millions	3 Months Ended						9 Months Ended		58 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Sales [Abstract]
Sales	$ 1,576.6			$ 1,872.4			$ 4,722.9	$ 5,311.1
Income before taxes:
Income before taxes	43.8			261.4			72.0	363.2
Corporate/Other:
Environmental income (expense)	(0.8)			(0.8)			23.0	5.9
Restructuring charges	(4.9)	$ (3.8)	$ (4.0)	(3.3)	$ (6.4)	$ (4.0)	(12.7)	(13.7)	$ (194.7)
Acquisition-related costs	0.0			(0.4)			0.0	(1.0)
Other operating income (expense)	0.1			(1.7)			0.3	6.4
Interest expense	(63.9)			(59.2)			(179.2)	(184.0)
Interest income	0.2			0.3			0.7	1.1
Non-operating pension income	4.1			5.4			12.2	16.2
Other income	0.0			0.0			11.2	0.0
Recoveries for costs incurred and expensed	0.0			(110.0)			(4.8)	(110.0)
Earnings (losses) of non-consolidated affiliates	0.0			0.4			0.0	(20.2)
Bay Gas non-cash impairment charge								21.5
Losses on disposition of property, plant and equipment				1.7			0.0	(1.9)
Gain in Other Operating (Expense) Income due to Insurance Recoveries								8.0
Chlor Alkali Products and Vinyls
Sales [Abstract]
Sales	876.3			1,051.1			2,657.7	3,005.9
Income before taxes:
Income before taxes	112.7			210.8			303.8	490.7
Epoxy
Sales [Abstract]
Sales	511.6			647.3			1,554.4	1,794.4
Income before taxes:
Income before taxes	24.2			31.1			38.6	33.8
Winchester
Sales [Abstract]
Sales	188.7			174.0			510.8	510.8
Income before taxes:
Income before taxes	13.9			10.3			33.1	34.1
Corporate/Other
Corporate/Other:
Environmental income (expense)	(0.8)			(110.8)			18.2	(104.1)
Other corporate and unallocated costs	(43.4)			(42.7)			(117.8)	(124.5)
Restructuring charges	(4.9)			(3.3)			(12.7)	(13.7)
Acquisition-related costs	$ 0.0			$ (0.4)			$ 0.0	(1.0)
Losses on disposition of property, plant and equipment								$ 1.7