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Income taxes - Component of Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income taxes
Expected tax expense (benefit), at U.S. federal statutory income tax rate of 21%	$ (1,726)	$ 9,425	$ (1,241)	$ 13,217
Rate differences on equity in earnings (losses) of Kronos, net of dividends	856	(954)	262	(2,512)
U.S. state income taxes and other, net	16	37	59	93
Income tax expense (benefit)	$ (854)	$ 8,508	$ (920)	$ 10,798

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Income tax reconciliation state income taxes and other net.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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