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, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	$ (1.6)	$ 8.8	$ (31.7)	$ 20.8
Kronos Worldwide, Inc.
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			(30.2)	15.3
NL
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			(3.1)	3.9
CompX
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			1.0	0.9
BMI
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			0.4	0.3
LandWell
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			$ 0.2	$ 0.4