Business and geographic segments - Additional Information (Detail)	Jun. 30, 2023
Kronos Worldwide, Inc. | Valhi Incorporation
Segment Reporting Information [Line Items]
Direct ownership percentage by parent	50.00%
Kronos Worldwide, Inc. | NL
Segment Reporting Information [Line Items]
Indirect controlling interest in subsidiary	31.00%
NL | Valhi Incorporation
Segment Reporting Information [Line Items]
Direct ownership percentage by parent	83.00%
LandWell | Valhi Incorporation
Segment Reporting Information [Line Items]
Direct ownership percentage by parent	27.00%
LandWell | BMI
Segment Reporting Information [Line Items]
Indirect controlling interest in subsidiary	50.00%
BMI | Valhi Incorporation
Segment Reporting Information [Line Items]
Direct ownership percentage by parent	63.00%