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Long-Term Debt - Revolving Credit Facility - Additional Information (Detail)
5 Months Ended 9 Months Ended
Apr. 20, 2021
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2021
EUR (€)
Line Of Credit Facility [Line Items]        
Revolving credit facility, borrowings     $ 0  
Kronos Worldwide, Inc. | Revolving North American Credit Facility        
Line Of Credit Facility [Line Items]        
Revolving credit facility, borrowings     $ 0  
Kronos Worldwide, Inc. | Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Line of credit maximum borrowing capacity $ 225,000,000      
Line of credit, maturity month and year 2026-04      
Revolving credit facility, borrowings   $ 0    
Amount available for borrowing $ 225,000,000      
Fixed charge coverage ratio, minimum value     100.00%  
Kronos Worldwide, Inc. | Revolving Credit Facility | Minimum | Variable Rate        
Line Of Credit Facility [Line Items]        
Interest rate on outstanding borrowings     1.50%  
Kronos Worldwide, Inc. | Revolving Credit Facility | Minimum | Base Rate Option        
Line Of Credit Facility [Line Items]        
Interest rate on outstanding borrowings     0.50%  
Kronos Worldwide, Inc. | Revolving Credit Facility | Maximum | Variable Rate        
Line Of Credit Facility [Line Items]        
Interest rate on outstanding borrowings     2.00%  
Kronos Worldwide, Inc. | Revolving Credit Facility | Maximum | Base Rate Option        
Line Of Credit Facility [Line Items]        
Interest rate on outstanding borrowings     2.00%  
Kronos Worldwide, Inc. | European Revolving Credit Facility        
Line Of Credit Facility [Line Items]        
Revolving credit facility, borrowings     $ 0  
Kronos Worldwide, Inc. | Canadian Subsidiary Revolving Borrowings Maximum        
Line Of Credit Facility [Line Items]        
Line of credit maximum borrowing capacity   $ 25,000,000 $ 25,000,000  
Kronos Worldwide, Inc. | Belgian Subsidiary Revolving Borrowings Maximum        
Line Of Credit Facility [Line Items]        
Line of credit maximum borrowing capacity | €       € 30,000,000
Kronos Worldwide, Inc. | German Subsidiary Revolving Borrowings Maximum        
Line Of Credit Facility [Line Items]        
Line of credit maximum borrowing capacity | €       € 60,000,000