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Stockholders' Equity - Additional Information (Detail)
12 Months Ended
Jul. 17, 2018
Vote
shares
Dec. 31, 2018
$ / shares
shares
Dec. 31, 2017
$ / shares
shares
Dec. 31, 2016
$ / shares
shares
Dec. 31, 2014
shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock, shares authorized 20,000,000        
Preferred stock, shares authorized 1,000 1,000 1,000    
Treasury stock purchases   0 0 0  
Shares available for purchase   678,000      
Common Stock Dividend declared by directors | $ / shares   $ 0.05 $ 0.05 $ 0.05  
2013 Director Stock Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Shares available for award   156,550      
Non-Employee | 2013 Director Stock Plan          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock shares authorized to be issued under the plan   200,000      
Class B Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock, vote per share | Vote 10        
Common stock, vote per share | Vote 1        
Common stock, shares issued   10,000,000    
Common stock, shares outstanding   10,000,000 10,000,000 10,000,000
Common stock, shares authorized   10,000,000    
Class A Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock, vote per share | Vote 1        
Common stock, shares issued   12,435,557 2,426,107    
Common stock, shares outstanding   12,435,557 2,426,107 2,419,107 2,411,107
Common stock, shares authorized   20,000,000 20,000,000    
NL Industries          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Conversion of common stock 10,000,000        
NL Industries | Class B Common Stock          
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]          
Common stock, shares issued 10,000,000        
Common stock, shares outstanding 10,000,000