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Marketable Securities - Schedule of Marketable Securities (Detail) - Level 1 - Valhi Inc - Common stock - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Available For Sale Securities [Line Items]
Market value	$ 26,877	$ 27,740
Cost basis	24,347	24,347
Unrealized gain	$ 2,530	$ 3,393

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- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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