v3.25.2
Long-term debt - Additional Information (Details) - NLKW Holding, LLC - Valhi - Valhi Credit Facility
$ in Millions
6 Months Ended
Jun. 30, 2025
USD ($)
Debt Instrument [Line Items]  
Maximum borrowing under credit facility $ 50.0
Borrowings or repayments under revolving credit facility 0.0
Outstanding borrowing 0.5
Amount available for future borrowing under revolving credit facility $ 49.5
Debt instrument, description of variable rate basis prime rate
Variable rate basis spread above reference rate 1.875%
Debt instrument average interest rate 9.38%