Noncontrolling interest in Subsidiaries - Noncontrolling Interest in Net Income (loss) of Subsidiaries (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries	$ 8.8	$ (6.7)	$ 20.8	$ (24.0)
Kronos Worldwide, Inc. | Reportable Legal Entities
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			15.3	(20.8)
NL | Reportable Legal Entities
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			3.9	(3.8)
CompX | Reportable Legal Entities
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			0.9	0.6
Basic Management Inc. | Reportable Legal Entities
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			0.3
LandWell | Reportable Legal Entities
Noncontrolling interest in net income (loss) of subsidiaries:
Noncontrolling interest in net income (loss) of subsidiaries			$ 0.4