Noncontrolling Interest in Subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries	$ 11.1	$ 8.7	$ 21.3	$ 27.2
Kronos Worldwide, Inc.
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries			11.6	29.0
NL Industries
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries			3.6	(4.8)
CompX International
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries			1.2	1.1
BMI
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries			2.0	0.7
LandWell
Noncontrolling interest in net income of subsidiaries:
Noncontrolling interest in net income of subsidiaries			$ 2.9	$ 1.2