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Marketable Securities - Classification of Marketable Securities (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2021
Dec. 31, 2022
Marketable Securities [Line Items]    
Market value $ 4.2 $ 3.2
Cost basis 3.3  
Unrealized gain (loss) 0.9  
Level 1 | Common stock | Valhi    
Marketable Securities [Line Items]    
Market value 4.1 3.2
Cost basis 3.2 $ 3.2
Unrealized gain (loss) 0.9  
Level 1 | Common stock | NL And CompX    
Marketable Securities [Line Items]    
Market value 0.1  
Cost basis $ 0.1