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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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