Business Segment Information - Additional Information (Detail)	Mar. 31, 2020
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	30.00%
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%