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Pension and Post-Employment Benefits - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Annual cash contribution		$ 0.4	$ 1.0
Percentage change in discount rate		0.25%
Amount change in PBO due to discount rate		$ 24.0
Amount change in net pension credit due to discount rate		0.1
Amount change in PBO due to change price inflation		$ 18.0
Percentage change in price inflation		0.25%
Amount change in net pension credit due price inflation		$ 1.1
Maximum percentage of Plan's assets invested in individual company's investment funds		5.00%
Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net pension credit, total	$ 5.6
Other Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Amount of contributions to defined contribution schemes		$ 10.4	$ 8.6
United Kingdom Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset allocation, actual		100.00%	100.00%	100.00%
United Kingdom Plan [Member] | Index-Tracking Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset allocation, actual			0.00%
Germany [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost, total		$ 0.1	$ 0.2	$ 0.2
Europe [Member] | Performance Chemicals [Member]
Defined Benefit Plan Disclosure [Line Items]
Post-employment obligations European businesses		4.5	$ 4.4
France [Member]
Defined Benefit Plan Disclosure [Line Items]
Amount of unrecognized actuarial net losses, net of tax		$ 0.2
Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of asset allocation, actual		12.00%	9.00%
Selling, General and Administrative Expenses [Member] | United Kingdom Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost, total		$ 0.9	$ 1.2	$ 0.9
Selling, General and Administrative Expenses [Member] | United Kingdom Plan [Member] | Forecast [Member]
Defined Benefit Plan Disclosure [Line Items]
Net service cost, total	$ 1.2

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