Noncontrolling interest in subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 2.7	$ 53.3	$ 15.0
Kronos Worldwide
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	(21.3)	16.1	(9.5)
NL Industries
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	(6.4)	11.4	(0.4)
CompX International
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	2.4	2.0	2.9
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	10.6	9.6	8.2
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 17.4	$ 14.2	$ 13.8