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Marketable securities - Schedule of Marketable Securities (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024
Marketable Securities [Line Items] |  |
Market value, Noncurrent assets | $ 18,900 | $ 28,015
Fair Value, Inputs, Level 1 [Member] | Valhi Inc | Common stock |  |
Marketable Securities [Line Items] |  |
Market value, Noncurrent assets | 18,900 | 28,015
Cost or amortized cost, Noncurrent assets | 24,347 | 24,347
Unrealized gain (loss), net Noncurrent assets | $ (5,447) | $ 3,668

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