Business Segment Information - Holding Percentage of Subsidiaries (Detail)	Sep. 30, 2019
Chemicals | Kronos Worldwide, Inc.
Segment Reporting Information [Line Items]
Controlling interest in subsidiary	80.00%
Component Products | CompX
Segment Reporting Information [Line Items]
Parent company ownership interest	86.00%
Real Estate Management And Development | BMI
Segment Reporting Information [Line Items]
Parent company ownership interest	63.00%
Real Estate Management And Development | LandWell | Aggregate General And Limited Interests
Segment Reporting Information [Line Items]
Controlling interest in subsidiary	77.00%