Income taxes - Component of Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Amount
Expected tax expense, at U.S. federal statutory income tax rate of 21%	$ 1,379	$ 273
Rate differences on equity in earnings (losses) of Kronos, net of dividends	(25)	(319)
U.S. state income taxes and other, net	118	23
Income tax expense (benefit)	$ 1,472	$ (23)
Percentage
U.S. federal statutory income tax rate (in %)	21.00%	21.00%