Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 333.3	$ 348.2
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	213.7	239.3
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	76.0	79.0
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	21.5	20.6
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	13.1	6.9
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 9.0	$ 2.4