Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 252.6	$ 258.2
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	142.8	147.9
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	40.1	39.5
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	15.8	15.3
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	30.3	31.6
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 23.6	$ 23.9