Investment in Kronos Worldwide, Inc. - Additional Information (Detail) - Kronos - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Mar. 31, 2021	Dec. 31, 2020
Schedule Of Equity Method Investments [Line Items]
Number of shares owned	35.2	35.2
Aggregate market value	$ 538.9	$ 525.1
Quoted market price per share	$ 15.30	$ 14.91

This item represents the aggregate value of each identified investment accounted for under the equity method of accounting based on the quoted market price for those investments in common stock for which a quoted market price is available.

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Balance held at close of period in number of shares.

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Price of a single share of a number of saleable stocks of a company.

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