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Marketable securities - Schedule of Marketable Securities (Details) - USD ($) $ in Millions | 9 Months Ended |
--- | --- | ---
Sep. 30, 2025 | Dec. 31, 2024
Marketable securities |  |
Market value, current | $ 3.1 | $ 1.9
Market value, noncurrent | 5.8 | 5.7
Noncurrent assets |  |
Marketable securities |  |
Unrealized gain, net | 0.3 |
Current assets |  |
Marketable securities |  |
Market value, current | 3.1 | 1.9
Cost or amortized cost | 3.1 | 1.9
Noncurrent assets |  |
Marketable securities |  |
Market value, noncurrent | 5.8 | 5.7
Cost or amortized cost | $ 5.5 | $ 5.7

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