Organization and basis of presentation - Additional Information (Detail)	Sep. 30, 2024 $ / shares
Significant Accounting Policies [Line Items]
Special dividend per share	$ 0.43
Kronos
Significant Accounting Policies [Line Items]
Parent company ownership interest	31.00%
Parent Company | Valhi Inc
Significant Accounting Policies [Line Items]
Parent company ownership interest	83.00%
Parent Company | Valhi Inc | Contran Corporation
Significant Accounting Policies [Line Items]
Parent company ownership interest	91.00%