Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 251.8	$ 243.5
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	140.7	134.5
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	45.9	44.3
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	16.7	16.4
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	24.7	24.6
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 23.8	$ 23.7