Marketable Securities - Additional Information (Detail) - Valhi Inc - Common stock - $ / shares shares in Millions	Jun. 30, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Number of shares owned	14.4	14.4
Quoted marked price per share	$ 2.97	$ 1.93

Balance held at close of period in number of shares.

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