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Income taxes - Additional Information (Details) - USD ($) $ in Thousands |  | 6 Months Ended
--- | --- | ---
Jul. 18, 2025 | Jun. 30, 2025 | Jun. 30, 2024
Income Tax Disclosure [Line Items] |  |  |
Dividends received from Kronos Worldwide, Inc. |  | $ 3,522 | $ 13,384
Foreign country | Subsequent Event |  |  |
Income Tax Disclosure [Line Items] |  |  |
Percentage of before current income tax expense (benefit) | 15.00% |  |
Percentage of reduction in enacted tax rate | 1.00% |  |
Percentage of after current income tax expense (benefit) | 10.00% |  |
Foreign country | Subsequent Event | Minimum |  |  |
Income Tax Disclosure [Line Items] |  |  |
Non-cash deferred income tax expense | $ 20,000 |  |
Foreign country | Subsequent Event | Maximum |  |  |
Income Tax Disclosure [Line Items] |  |  |
Non-cash deferred income tax expense | $ 23,000 |  |
Kronos |  |  |
Income Tax Disclosure [Line Items] |  |  |
Dividends received from Kronos Worldwide, Inc. |  | $ 3,500 | $ 13,400

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