Noncontrolling interest in subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 5.8	$ 1.2
Kronos Worldwide, Inc.
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	1.5	(3.0)
NL
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	1.2	(1.1)
CompX
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	0.5	0.8
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	1.0	1.7
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 1.6	$ 2.8