| **Document Information** | Feb. 12, 2024       |
|--------------------------|---------------------|
| **Cover [Abstract]**     |                |
| Document Type            | 8-K                 |
| Amendment                | false               |
| CIK                      | 0000072162          |
| Registrant Name          | NL Industries, Inc. |
| Period End Date          | Feb. 12,  2024      |

| X                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
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Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.
+ References
No definition available.
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| X                                                                                                                                                                                                        |
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| - Definition
Cover page.
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No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |
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| - Definition
For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period.  The format of the date is YYYY-MM-DD.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                    |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.
+ References
No definition available.
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                            |
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| - Definition
A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
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| - Definition
The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Exchange Act -Number 240 -Section 12 -Subsection b-2
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