Noncontrolling interest in Subsidiaries - Schedule of Noncontrolling Interest in Net Income (Loss) of Subsidiaries (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	$ 6.0	$ (1.6)	$ 4.3	$ (31.7)
Kronos Worldwide, Inc.
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			3.8	(30.2)
NL Industries
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			1.0	(3.1)
CompX International
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			1.0	1.0
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			(1.2)	0.4
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			$ (0.3)	$ 0.2