Noncontrolling interest in Subsidiaries - Schedule of Noncontrolling Interest in Net Income of Subsidiaries (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	$ 38.8	$ 95.1	$ 12.9
Kronos Worldwide, Inc.
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	39.9	69.3	8.3
NL Industries
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	(7.0)	19.7	2.6
CompX International
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	2.0	1.7	1.4
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	1.5	3.2	(0.4)
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	$ 2.4	$ 1.2	$ 1.0