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Summary of significant accounting policies - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Schedule Of Significant Accounting Policies [Line Items]      
Total number of weeks in a fiscal year 52 52 52
Advertising costs $ 372,000 $ 386,000 $ 319,000
Depreciation expense on property plant and equipment 3,100,000 3,500,000 3,900,000
Defined contribution plan expense 1,800,000 1,700,000 1,500,000
Undistributed earnings of foreign subsidiaries 0 0  
Uncertain tax positions reserve 0 0  
Weighted average number of outstanding stock options excluded from calculation of diluted earnings per share 0 9,200 27,000
NL [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Percentage of ownership held by parent company 87.00%    
Income tax payments to NL $ 1,200,000 $ 3,700,000 $ 2,200,000
Valhi [Member] | NL [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Percentage of ownership held by parent company 83.00%    
Contran Corporation [Member] | Valhi [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Percentage of ownership held by parent company 93.00%    
Buildings [Member] | Minimum [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Property and equipment, estimated useful lives 15 years    
Buildings [Member] | Maximum [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Property and equipment, estimated useful lives 40 years    
Equipment and software [Member] | Minimum [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Property and equipment, estimated useful lives 3 years    
Equipment and software [Member] | Maximum [Member]
      
Schedule Of Significant Accounting Policies [Line Items]      
Property and equipment, estimated useful lives 20 years