Investment in Kronos Worldwide, Inc. - Additional Information (Detail) (Kronos, USD $) In Millions, except Per Share data, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Kronos
Schedule Of Change In Carrying Value Of Equity Investment [Line Items]
Outstanding common stock, shares	35.2	35.2
Aggregate market value	$ 551.9	$ 670.9
Quoted market price per share	$ 15.67	$ 19.05

Balance held at close of period in number of shares.

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