Marketable Securities - Additional Information (Detail) - Valhi Inc - Common stock - $ / shares shares in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Number of shares owned	14.4	14.4
Quoted marked price per share	$ 1.93	$ 6.17

Balance held at close of period in number of shares.

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