Noncontrolling Interest in Subsidiaries - Noncontrolling Interest in Subsidiaries (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 364.9	$ 391.5
Kronos Worldwide, Inc. | Reportable Legal Entities
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	234.7	241.9
NL | Reportable Legal Entities
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	58.8	74.5
CompX | Reportable Legal Entities
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	14.3	13.6
Basic Management Inc. | Reportable Legal Entities
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	31.8	33.7
LandWell | Reportable Legal Entities
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 25.3	$ 27.8