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Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Mar. 31, 2020 | Jun. 30, 2021 | Jun. 30, 2020 | Dec. 31, 2020 | Dec. 31, 2019
Income Tax Disclosure [Line Items] |  |  |  |  |
Dividends received from Kronos Worldwide, Inc. |  | $ 12,678 | $ 12,678 |  |
Kronos |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Dividends received from Kronos Worldwide, Inc. |  | $ 12,700 | $ 12,700 |  |
Kronos | CARES Act |  |  |  |  |
Income Tax Disclosure [Line Items] |  |  |  |  |
Cash tax benefit due to reversal of valuation allowance | $ 500 |  |  |  |
Percentage of adjusted taxable income |  |  |  | 50.00% | 30.00%

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