Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 328.9	$ 324.4
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	226.6	212.3
NL
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	75.7	67.1
CompX
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	22.5	23.5
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	8.3	14.7
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ (4.2)	$ 6.8