Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 335.6	$ 348.2
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	222.0	239.3
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	76.6	79.0
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	21.1	20.6
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	10.3	6.9
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 5.6	$ 2.4