Business segment information - Additional Information (Detail)	Sep. 30, 2024
Kronos Worldwide, Inc. | Valhi Incorporation
Business segment information [Line Items]
Direct ownership percentage by parent	50.00%
Kronos Worldwide, Inc. | NL
Business segment information [Line Items]
Indirect controlling interest in subsidiary	31.00%
NL | Valhi Incorporation
Business segment information [Line Items]
Direct ownership percentage by parent	83.00%
LandWell | Valhi Incorporation
Business segment information [Line Items]
Direct ownership percentage by parent	27.00%
LandWell | Basic Management Inc
Business segment information [Line Items]
Indirect controlling interest in subsidiary	50.00%
Basic Management Inc | Valhi Incorporation
Business segment information [Line Items]
Direct ownership percentage by parent	63.00%