Segments - Recon. of Net Income to Segment Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Income (loss) before income taxes	$ 101.2	$ 56.3	$ (63.7)	$ (48.2)	$ (17.5)	$ 31.8	$ 43.7	$ 46.6	$ 45.7	$ 104.6	$ 364.3
Interest expense, net									(43.6)	(39.3)	(46.4)
Depreciation and amortization									134.3	136.0	130.2
Corporate Unallocated									82.1	85.4	88.0
Adjusted EBITDA addbacks									75.9	71.9	32.3
Adjusted EBITDA									381.6	437.2	661.2
Loss on extinguishment of long-term debt											0.2
Net (gain) loss on disposition of businesses and assets									(0.4)	(0.7)	(1.0)
Restructuring and other charges									9.9	18.1	8.2
Acquisition transactions and integration net costs (benefit)									9.1	(0.9)	0.6
Asset impairment charges or write-offs									39.1		1.5
Other items									25.5	55.4	22.8
Income from settlement of value added tax liabilities					$ 32.7	$ 7.4
Fees for secondary offering									146.0	198.6	258.4
Arkema | Foreign Exchange Forward Contracts
Segment Reporting Information [Line Items]
Acquisition purchase price hedge gain									(7.3)
Corporate Unallocated [Member]
Segment Reporting Information [Line Items]
Interest expense, net									(43.6)	(39.3)	(46.4)
Depreciation and amortization									$ 17.9	$ 13.3	$ 9.0