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Investment in Kronos Worldwide, Inc. - Additional Information (Detail) - Kronos - USD ($) $ / shares in Units, shares in Millions, $ in Millions | Sep. 30, 2016 | Dec. 31, 2015
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Schedule Of Equity Method Investments [Line Items] |  |
Outstanding common stock, shares | 35.2 | 35.2
Aggregate market value | $ 292.0 | $ 198.6
Common stock quoted market price per share | $ 8.29 | $ 5.64

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