Noncontrolling Interest in subsidiaries - Noncontrolling Interest in Subsidiaries (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 345.7	$ 358.1
Kronos Worldwide, Inc. [Member]
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	251.2	267.0
NL [Member]
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	81.3	77.8
CompX [Member]
Noncontrolling interest in net assets:
Noncontrolling interest in subsidiaries	$ 13.2	$ 13.3