Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Net Assets of Subsidiaries (Detail) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 243.5	$ 258.2
Kronos Worldwide, Inc.
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	134.5	147.9
NL Industries
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	44.3	39.5
CompX International
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	16.4	15.3
BMI
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	24.6	31.6
LandWell
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 23.7	$ 23.9