Organization and basis of presentation - Additional Information (Detail) |
3 Months Ended |
|---|---|
Mar. 31, 2026 | |
| Valhi Inc | Parent Company | |
| Summary of significant accounting policies [Line Items] | |
| Parent company ownership interest | 50.00% |
| Valhi Inc | NL Industries Inc. | |
| Summary of significant accounting policies [Line Items] | |
| Ownership percentage in company | 83.00% |
| NL Industries Inc. | Parent Company | |
| Summary of significant accounting policies [Line Items] | |
| Parent company ownership interest | 31.00% |
| Contran | |
| Summary of significant accounting policies [Line Items] | |
| Controlling interest description | Consequently, at March 31, 2026, Ms. Simmons and the Family Trust may be deemed to control Contran, and therefore may be deemed to indirectly control the wholly-owned subsidiary of Contran, Valhi, NL and us. |
| Contran | Valhi Inc | |
| Summary of significant accounting policies [Line Items] | |
| Ownership percentage of parent company held by related party | 91.00% |