Organization and basis of presentation (Policies)	9 Months Ended
Organization and basis of presentation (Policies)	Sep. 30, 2013
Organization	Organization - At September 30, 2013, (i) Valhi, Inc. (NYSE: VHI) held approximately 83% of our outstanding common stock and (ii) Contran Corporation and its subsidiaries held an aggregate of approximately 94% of Valhi’s outstanding common stock. Substantially all of Contran’s outstanding voting stock is held by trusts established for the benefit of certain children and grandchildren of Harold C. Simmons (for which Mr. Simmons is the sole trustee), or is held by Mr. Simmons or other persons or companies related to Mr. Simmons. Consequently, Mr. Simmons may be deemed to control Contran, Valhi and us.
Basis of presentation	Basis of presentation - Consolidated in this Quarterly Report are the results of our majority-owned subsidiary, CompX International Inc. We also own 30% of Kronos Worldwide, Inc., CompX (NYSE MKT: CIX) and Kronos (NYSE: KRO) each file periodic reports with the Securities and Exchange Commission (SEC). The unaudited Condensed Consolidated Financial Statements contained in this Quarterly Report have been prepared on the same basis as the audited Consolidated Financial Statements in our Annual Report on Form 10-K for the year ended December 31, 2012 that we filed with the SEC on March 12, 2013 (the 2012 Annual Report). In our opinion, we have made all necessary adjustments (which include only normal recurring adjustments) in order to state fairly, in all material respects, our consolidated financial position, results of operations and cash flows as of the dates and for the periods presented. We have condensed the Consolidated Balance Sheet and Statement of Stockholders’ Equity at December 31, 2012 contained in this Quarterly Report as compared to our audited Consolidated Financial Statements at that date and we have omitted certain information and footnote disclosures (including those related to the Consolidated Balance Sheet at December 31, 2012) normally included in financial statements prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). Our results of operations for the interim periods ended September 30, 2013 may not be indicative of our operating results for the full year. The Condensed Consolidated Financial Statements contained in this Quarterly Report should be read in conjunction with our 2012 Consolidated Financial Statements contained in our 2012 Annual Report. Unless otherwise indicated, references in this report to “NL,” “we,” “us” or “our” refer to NL Industries, Inc. and its subsidiaries and affiliate, Kronos, taken as a whole.
Consolidation	Consolidated in this Quarterly Report are the results of our majority-owned subsidiary, CompX International Inc.
Equity Method Investments	We also own 30% of Kronos Worldwide, Inc.,
Commitments and Contingencies	We believe that these actions are without merit, and we intend to continue to deny all allegations of wrongdoing and liability and to defend against all actions vigorously. We do not believe it is probable that we have incurred any liability with respect to all of the lead pigment litigation cases to which we are a party, and liability to us that may result, if any, in this regard cannot be reasonably estimated, because: we have never settled any of the market share, risk contribution, intentional tort, fraud, nuisance, supplier negligence, breach of warranty, conspiracy, misrepresentation, aiding and abetting, enterprise liability, or statutory cases, no final, non-appealable adverse verdicts have ever been entered against us and we have never ultimately been found liable with respect to any such litigation matters, including over 100 cases over a twenty-year period for which we were previously a party and for which we have been dismissed without any finding of liability. Accordingly, we have not accrued any amounts for any of the pending lead pigment and lead-based paint litigation cases. In addition, we have determined that liability to us which may result, if any, cannot be reasonably estimated because there is no prior history of a loss of this nature on which an estimate could be made and there is no substantive information available upon which an estimate could be based.
Environmental Matters and Litigation	Environmental matters and litigation Our operations are governed by various environmental laws and regulations. Certain of our businesses are and have been engaged in the handling, manufacture or use of substances or compounds that may be considered toxic or hazardous within the meaning of applicable environmental laws and regulations. As with other companies engaged in similar businesses, certain of our past and current operations and products have the potential to cause environmental or other damage. We have implemented and continue to implement various policies and programs in an effort to minimize these risks. Our policy is to maintain compliance with applicable environmental laws and regulations at all of our plants and to strive to improve environmental performance. From time to time, we may be subject to environmental regulatory enforcement under U.S. and non-U.S. statutes, the resolution of which typically involves the establishment of compliance programs. It is possible that future developments, such as stricter requirements of environmental laws and enforcement policies, could adversely affect our production, handling, use, storage, transportation, sale or disposal of such substances. We believe that all of our facilities are in substantial compliance with applicable environmental laws. Certain properties and facilities used in our former operations, including divested primary and secondary lead smelters and former mining locations, are the subject of civil litigation, administrative proceedings or investigations arising under federal and state environmental laws and common law. Additionally, in connection with past operating practices, we are currently involved as a defendant, potentially responsible party (PRP) or both, pursuant to the Comprehensive Environmental Response, Compensation and Liability Act, as amended by the Superfund Amendments and Reauthorization Act (CERCLA), and similar state laws in various governmental and private actions associated with waste disposal sites, mining locations, and facilities that we or our predecessors, our subsidiaries or their predecessors currently or previously owned, operated or used, certain of which are on the United States Environmental Protection Agency’s (EPA) Superfund National Priorities List or similar state lists. These proceedings seek cleanup costs, damages for personal injury or property damage and/or damages for injury to natural resources. Certain of these proceedings involve claims for substantial amounts. Although we may be jointly and severally liable for these costs, in most cases we are only one of a number of PRPs who may also be jointly and severally liable, and among whom costs may be shared or allocated. In addition, we are also a party to a number of personal injury lawsuits filed in various jurisdictions alleging claims related to environmental conditions alleged to have resulted from our operations. Obligations associated with environmental remediation and related matters are difficult to assess and estimate for numerous reasons including the: complexity and differing interpretations of governmental regulations, number of PRPs and their ability or willingness to fund such allocation of costs, financial capabilities of the PRPs and the allocation of costs among them, solvency of other PRPs, multiplicity of possible solutions, number of years of investigatory, remedial and monitoring activity required, uncertainty over the extent, if any, to which our former operations might have contributed to the conditions allegedly giving rise to such personal injury, property damage, natural resource and related claims and number of years between former operations and notice of claims and lack of information and documents about the former operations. In addition, the imposition of more stringent standards or requirements under environmental laws or regulations, new developments or changes regarding site cleanup costs or the allocation of costs among PRPs, solvency of other PRPs, the results of future testing and analysis undertaken with respect to certain sites or a determination that we are potentially responsible for the release of hazardous substances at other sites, could cause our expenditures to exceed our current estimates. We cannot assure you that actual costs will not exceed accrued amounts or the upper end of the range for sites for which estimates have been made, and we cannot assure you that costs will not be incurred for sites where no estimates presently can be made. Further, additional environmental and related matters may arise in the future. If we were to incur any future liability, this could have a material adverse effect on our consolidated financial statements, results of operations and liquidity. We record liabilities related to environmental remediation and related matters when estimated future expenditures are probable and reasonably estimable. We adjust such accruals as further information becomes available to us or as circumstances change. Unless the amounts and timing of such estimated future expenditures are fixed and reasonably determinable, we generally do not discount estimated future expenditures to their present value due to the uncertainty of the timing of the payout. We recognize recoveries of costs from other parties, if any, as assets when their receipt is deemed probable. At September 30, 2013 and December 31, 2012, we have not recognized any receivables for recoveries.
Insurance Coverage Claims	Insurance coverage claims We are involved in certain legal proceedings with a number of our former insurance carriers regarding the nature and extent of the carriers’ obligations to us under insurance policies with respect to certain lead pigment and asbestos lawsuits. The issue of whether insurance coverage for defense costs or indemnity or both will be found to exist for our lead pigment and asbestos litigation depends upon a variety of factors and we cannot assure you that such insurance coverage will be available. We have agreements with three former insurance carriers pursuant to which the carriers reimburse us for a portion of our future lead pigment litigation defense costs, and one such carrier reimburses us for a portion of our future asbestos litigation defense costs. We are not able to determine how much we will ultimately recover from these carriers for defense costs incurred by us because of certain issues that arise regarding which defense costs qualify for reimbursement. While we continue to seek additional insurance recoveries, we do not know if we will be successful in obtaining reimbursement for either defense costs or indemnity. Accordingly, we recognize insurance recoveries in income only when receipt of the recovery is probable and we are able to reasonably estimate the amount of the recovery.

Disclosure of accounting policy for commitments and contingencies, which may include policies for recognizing and measuring loss and gain contingencies.

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- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

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- Definition

Disclosure of accounting policy for the equity method of accounting for investments in common stock or other interests including unconsolidated subsidiaries, corporate joint ventures, noncontrolling interests in real estate ventures, limited partnerships, and limited liability companies. The accounting policy may include information such as: (1) initially recording an investment in the stock of an investee at cost; (2) adjusting the carrying amount of the investment to recognize the investor's share of the earnings or losses of the investee after the date of acquisition; and (3) adjustments to reflect the investor's share of changes in the investee's capital (dividends). This disclosure may also include a detailed description of the policy for determining the amount of equity method losses recognized after an investment has been reduced to zero as a result of previous losses, reasons for not using the equity method when the investor company owns 20 percent or more of the voting stock of the investee's company (including identification of the significant investee), reasons for using the equity method when the ownership percentage is less than 20 percent, and discussion of recognition of equity method losses when an investor's total investment in an investee includes, in addition to an investment in common stock, other investments such as preferred stock and loans to the investee. An entity also may describe how such investments are assessed for impairment.

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