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Marketable Securities (Tables) | 12 Months Ended
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Dec. 31, 2021
Investments Debt And Equity Securities [Abstract] |
Schedule of Marketable Securities | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Fair value | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | measurement | ​ | Market | ​ | Cost | ​ | Unrealized
​ |  | level |  | value |  | basis |  | gain (loss)
​ | ​ | ​ | ​ | (In thousands)
December 31, 2020 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Noncurrent assets | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Valhi common stock |  | 1 | ​ | $ | 18,206 | ​ | $ | 24,347 | ​ | $ | (6,141)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
December 31, 2021 | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Noncurrent assets | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Valhi common stock |  | 1 | ​ | $ | 34,435 | ​ | $ | 24,347 | ​ | $ | 10,088

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- Definition Tabular disclosure of the reconciliation of available-for-sale securities from cost basis to fair value. + References No definition available. + Details
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