Noncontrolling interest in subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 325.7	$ 348.2
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	209.0	239.3
NL Industries, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	76.9	79.0
CompX International Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	22.0	20.6
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	11.0	6.9
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 6.8	$ 2.4