v3.26.1
Fair value measurements and financial instruments - Financial Instruments not Carried at Fair Value (Details) - USD ($)
$ in Millions
Jun. 30, 2026
Dec. 31, 2025
Reported Value Measurement    
Fair value measurements and financial instruments    
Cash, cash equivalents and restricted cash equivalents $ 222.3 $ 228.7
Estimate of Fair Value Measurement    
Fair value measurements and financial instruments    
Cash, cash equivalents and restricted cash equivalents 222.3 228.7
Kronos Worldwide | Kronos International, Inc    
Fair value measurements and financial instruments    
Long term debt, carrying amount 28.2  
Long term debt, fair value 28.2  
Kronos Worldwide | 9.50% Senior Secured Notes due 2029 | Kronos International, Inc    
Fair value measurements and financial instruments    
Long term debt, carrying amount 487.7 503.7
Long term debt, fair value 478.8 469.9
LandWell | Bank note payable    
Fair value measurements and financial instruments    
Long term debt, carrying amount 10.3 10.7
Long term debt, fair value $ 10.3 $ 10.7