Noncontrolling interest in subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 9.8	$ 2.9	$ 15.6	$ 4.1
Kronos Worldwide, Inc.
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			5.1	(4.5)
NL
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			2.5	(1.7)
CompX
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			1.1	1.3
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			2.7	3.5
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income of subsidiaries			$ 4.2	$ 5.5