Long-term debt - Valhi Contran Credit Facility - Additional Information (Detail) - VALHI, INC. - Contran Credit Facility $ in Millions	6 Months Ended
	Jun. 30, 2024 USD ($)
Debt Instrument [Line Items]
Borrowings of credit facility	$ 0.0
Repayments of credit facility	$ 30.8
Debt instrument, interest rate during period	9.50%
Debt instrument, Interest rate at period end	9.50%
Amount available for borrowing	$ 87.4