Restructuring (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		24 Months Ended
	Jan. 31, 2020	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		$ 7.5	$ (0.3)	$ 10.6	$ 0.1
Proceeds received on sale of property	$ 1.3					$ 12.5
Gain on sale of land				0.6
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	17.9			17.9
Expenses				7.1
Payments/Deductions				(7.9)
Accrued charges/Balance at end of period		17.1		17.1		17.9
Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		6.5		9.3
Cumulative life-to-date charges		27.1		27.1
Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.1	(0.4)	0.2	(0.2)
Cumulative life-to-date charges		6.3		6.3
Expected restructuring charges		1.0		1.0
Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			0.1	0.2	0.3
Cumulative life-to-date charges		24.8		24.8
Other Restructurings
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.9		0.9
Asset Impairment And Accelerated Depreciation [Member] | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		3.1		3.1
Asset Impairment And Accelerated Depreciation [Member] | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		14.7		14.7
Accelerated Depreciation | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.2		2.5
Cumulative life-to-date charges		2.9		2.9
Restructuring Reserve [Roll Forward]
Expenses		1.2
Employee Termination Benefit Charges
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	17.2			17.2
Expenses				6.7
Payments/Deductions				(7.0)
Accrued charges/Balance at end of period		16.9		16.9		17.2
Employee Termination Benefit Charges | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		4.1		4.4
Cumulative life-to-date charges		21.4		21.4
Restructuring Reserve [Roll Forward]
Expenses		4.1
Employee Termination Benefit Charges | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			(0.4)		(0.4)
Cumulative life-to-date charges		0.7		0.7
Employee Termination Benefit Charges | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		5.4		5.4
Share-Based Compensation Benefit [Member] | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.4
Pension Benefits [Member] | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Expected restructuring charges		1.0		1.0
Contract Termination
Restructuring Reserve [Roll Forward]
Accrued charges/Balance at beginning of period	$ 0.7			0.7
Payments/Deductions				(0.5)
Accrued charges/Balance at end of period		0.2		0.2		$ 0.7
Contract Termination | Corporate Restructuring Program
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		1.2		2.4
Cumulative life-to-date charges		2.8		2.8
Restructuring Reserve [Roll Forward]
Expenses		1.2
Contract Termination | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		0.3		0.3
Contract Termination | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Cumulative life-to-date charges		0.3		0.3
Decommissioning and Other Charges
Restructuring Reserve [Roll Forward]
Expenses				0.4
Payments/Deductions				(0.4)
Decommissioning and Other Charges | Terneuzen Plant Modernization
Restructuring Cost and Reserve [Line Items]
Restructuring Charges		0.1		0.2	0.2
Cumulative life-to-date charges		2.2		2.2
Decommissioning and Other Charges | Livorno Plant Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring Charges			$ 0.1	0.2	$ 0.3
Cumulative life-to-date charges		$ 4.4		$ 4.4