Noncontrolling Interest in Subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 13.5	$ 10.2
Kronos Worldwide, Inc.
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	5.2	5.9
NL Industries
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	0.3	2.6
CompX International
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	0.6	0.5
BMI
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	2.8	0.5
LandWell
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 4.6	$ 0.7