Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Income Statement (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Schedule Of Equity Method Investments [Line Items]
Net sales	$ 40,569	$ 40,272
Cost of sales	27,317	28,109
Income from operations	4,107	3,148
Income tax expense	1,472	(23)
Net income (loss)	4,344	667
Kronos | Reportable Legal Entities
Schedule Of Equity Method Investments [Line Items]
Net sales	509,800	489,800
Cost of sales	426,500	383,000
Income from operations	12,600	38,400
Income tax expense	2,800	7,600
Net income (loss)	$ (4,800)	$ 18,100