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Stockholder's Equity - Additional Information (Detail) - CompX $ in Thousands | 6 Months Ended
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Jun. 30, 2021 USD ($) shares
Class Of Stock [Line Items] |
Number of shares available for purchase under repurchase authorizations | 627,547
Common Class A [Member] |
Class Of Stock [Line Items] |
Number of shares purchased in market transaction | 50,000
Value of of shares purchased in market transaction | $ | $ 755,000

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