Noncontrolling interest in subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 6.6	$ 9.8	$ 12.5	$ 15.6
Kronos Worldwide
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			1.6	5.1
NL Industries
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			0.2	2.5
CompX International
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			1.4	1.1
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			3.3	2.7
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			$ 6.0	$ 4.2