Investment in Kronos Worldwide, Inc. - Changes in Carrying Value of Investment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Schedule Of Equity Method Investments [Line Items]
Balance at the beginning of the period	$ 230,088
Equity in losses of Kronos	(1,477)	$ 5,525
Dividends received from Kronos	(1,761)	$ (1,761)
Equity in Kronos' other comprehensive income (loss):
Balance at the end of the period	228,245
Kronos
Schedule Of Equity Method Investments [Line Items]
Balance at the beginning of the period	230,100
Equity in losses of Kronos	(1,500)
Dividends received from Kronos	(1,800)
Equity in Kronos' other comprehensive income (loss):
Currency translation	1,300
Balance at the end of the period	228,200
Kronos | Defined benefit pension plans
Equity in Kronos' other comprehensive income (loss):
Defined benefit pension plans	$ 100