Investment in Kronos Worldwide, Inc. - Selected Financial Information of Kronos Balance Sheet (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 155,861	$ 159,903
Property and equipment, net	23,453	23,709
Other noncurrent assets	935	931
Total assets	461,192	464,220
Current liabilities	14,628	20,580
Other noncurrent liabilities	1,199	1,277
Stockholders' equity	359,329	358,769
Total liabilities and equity	461,192	464,220
Kronos | Reportable Legal Entities
Schedule Of Equity Method Investments [Line Items]
Current assets	988,500	994,500
Property and equipment, net	712,600	724,300
Other noncurrent assets	97,200	98,000
Total assets	1,798,300	1,816,800
Current liabilities	311,000	368,800
Long-term debt	602,700	557,400
Accrued pension costs	76,400	80,900
Other noncurrent liabilities	63,200	58,600
Stockholders' equity	745,000	751,100
Total liabilities and equity	$ 1,798,300	$ 1,816,800