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Marketable Securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Schedule Of Available For Sale Securities [Line Items] |  |
Market value | $ 34,435 | $ 18,206
Level 1 | Valhi Inc | Common stock |  |
Schedule Of Available For Sale Securities [Line Items] |  |
Market value | 34,435 | 18,206
Cost basis | 24,347 | 24,347
Unrealized gain (loss) | $ 10,088 | $ (6,141)

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