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Other Intangible Assets - Summary of Other Intangible Assets (Detail) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Dec. 31, 2024
Gross cost at January 1 | $ 331.8 |  |
Additions | 17.0 |  |
Exchange effect | 17.8 |  |
Gross cost at March 31 | 366.6 |  |
Accumulated amortization at January 1 | (266.4) |  |
Amortization expense | (9.3) | $ (9.6) |
Impairment | (19.1) |  |
Exchange effect | (8.5) |  |
Accumulated amortization at March 31 | (303.3) |  |
Net book amount at March 31 | $ 63.3 |  | $ 65.4

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