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Pension and Post-Employment Benefits - Additional Information (Detail) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2024 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension scheme settlement charge |  | $ 0.0 | $ 155.6 | $ 0.0
Pension asset |  | 0.0 | 2.4 |
Annual cash contribution |  |  | 0.0 |
Income tax expense |  | (21.5) | (5.6) | (35.3)
Amount of unrecognized actuarial net losses, net of tax |  | 0.9 | (21.3) | (17.5)
Other Plans [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Amount of contributions to defined contribution schemes |  | 15.3 | 13.9 |
United Kingdom Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension asset |  | 0.0 | 2.5 | $ 459.2
Asset |  | 0.0 | 2.4 |
Funds to cover pension related costs | $ 8.4 | (0.9) | (8.4) |
Income tax expense |  |  | $ (2.1) |
Percentage of asset allocation, actual |  |  | 100.00% | 100.00%
United Kingdom Plan [Member] | Pension Plan [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Projected Benefit Obligation |  | 0.0 | $ 0.1 | $ 424.1
Europe [Member] | Performance Chemicals [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Post-employment obligations European businesses |  | 3.8 | 4.1 |
France [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Amount of unrecognized actuarial net losses, net of tax |  | $ 0.1 | $ 0.2 |

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