Cover [Abstract] Document Information [Table] Document Information [Line Items] Document Type Document Type Document Quarterly Report Document Quarterly Report Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Transition Report Document Transition Report Securities Act File Number Entity File Number Entity Registrant Name Entity Registrant Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address, Address Line One Entity Address, Address Line Two Entity Address, Address Line Two Entity Address, City or Town Entity Address, City or Town Entity Address, State or Province Entity Address, State or Province Entity Address, Postal Zip Code Entity Address, Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Title of 12(b) Security Title of 12(b) Security Trading Symbol Trading Symbol Security Exchange Name Security Exchange Name Entity Current Reporting Status Entity Current Reporting Status Entity Interactive Data Current Entity Interactive Data Current Entity Filer Category Entity Filer Category Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Shell Company Entity Shell Company Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Document Fiscal Period Focus Document Fiscal Period Focus Amendment Flag Amendment Flag CONDENSED CONSOLIDATED BALANCE SHEETS Statement [Table] Statement [Table] Class of Stock [Axis] Class of Stock Class of Stock [Domain] Class of Stock Common Class A [Member] Class A common stock Statement [Line Items] Statement [Line Items] Assets [Abstract] ASSETS Assets, Current [Abstract] Current assets: Cash and Cash Equivalent Cash and cash equivalents Accounts Receivable, after Allowance for Credit Loss, Current Accounts receivable, net Total accounts receivable, net Inventory, Net Inventories, net Total inventories, net Prepaid Expense and Other Assets, Current Prepaid expenses and other Assets, Current Total current assets Asset noncurrent other than property plant equipment. Asset Noncurrent Other Than Property Plant Equipment [Abstract] Other assets: Other Receivable, after Allowance for Credit Loss, Noncurrent Note receivable from affiliate Goodwill Goodwill Operating Lease, Right-of-Use Asset Operating lease right-of-use asset Other Assets, Noncurrent Other noncurrent assets Assets, Noncurrent, Other than Noncurrent Investments and Property, Plant and Equipment Total other assets Property, Plant and Equipment, Net [Abstract] Property and equipment: Land Land Buildings and Improvements, Gross Buildings Machinery and Equipment, Gross Equipment Construction in Progress, Gross Construction in progress Property, Plant and Equipment, Gross Gross property and equipment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Less accumulated depreciation Property, Plant and Equipment, Net Net property and equipment Assets Total assets Liabilities and Equity [Abstract] LIABILITIES AND STOCKHOLDERS' EQUITY Liabilities, Current [Abstract] Current liabilities: Accounts Payable and Accrued Liabilities, Current Accounts payable and accrued liabilities Total accounts payable and accrued liabilities Operating Lease, Liability, Current Operating lease liability Other Liabilities, Current Income taxes payable to affiliate Liabilities, Current Total current liabilities Liabilities, Noncurrent [Abstract] Noncurrent liabilities: Deferred Income Tax Liabilities, Net Deferred income taxes Operating Lease, Liability, Noncurrent Operating lease liability Other Liabilities, Noncurrent Other Liabilities, Noncurrent Total noncurrent liabilities Equity, Attributable to Parent [Abstract] Stockholders' equity: Preferred Stock, Value, Issued Preferred stock Common Stock, Value, Issued Class A common stock Additional Paid in Capital, Common Stock Additional paid-in capital Retained Earnings (Accumulated Deficit) Retained earnings Equity, Attributable to Parent Balance Balance Total stockholders' equity Liabilities and Equity Total liabilities and stockholders' equity CONDENSED CONSOLIDATED STATEMENTS OF INCOME Revenue from Contract with Customer, Excluding Assessed Tax Net sales Total net sales Cost of Product and Service Sold Cost of sales Total Cost of sales Gross Profit Gross margin Total Gross margin Selling, General and Administrative Expense Selling, general and administrative expense Total Segment selling, general and administrative expense Operating Income (Loss) Total operating income Operating income Interest and Dividend Income, Securities, Operating Interest income Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income before income taxes Income Tax Expense (Benefit) Income tax expense Income tax expense Net Income (Loss) Attributable to Parent Net income Net income Earnings Per Share, Basic Net income per basic share Earnings Per Share, Diluted Net income per diluted share Weighted Average Number of Shares Outstanding, Basic Weighted average shares outstanding - basic Weighted Average Number of Shares Outstanding, Diluted Weighted average shares outstanding - diluted CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY Equity Components [Axis] Equity Components Equity Component [Domain] Equity Component Common Stock [Member] Common stock Additional Paid-in Capital [Member] Additional paid-in capital Retained Earnings [Member] Retained earnings Dividends, Common Stock, Cash Cash dividends Common Stock, Dividends, Per Share, Cash Paid Cash dividends per share CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Cash flows from operating activities: Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net income Depreciation, Depletion and Amortization Depreciation and amortization Deferred Income Tax Expense (Benefit) Deferred income taxes Other Noncash Income (Expense) Other, net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Change in assets and liabilities: Increase (Decrease) in Accounts Receivable Accounts receivable, net Increase (Decrease) in Inventories Inventories, net Increase (Decrease) in Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities Increase (Decrease) in Due to Affiliates Accounts with affiliates Increase (Decrease) in Prepaid Expense and Other Assets Prepaids and other, net Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Net cash used in operating activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Cash flows from investing activities: Payments to Acquire Property, Plant, and Equipment Capital expenditures, net Payments for (Proceeds from) Investments [Abstract] Note receivable from affiliate: Repayment of Notes Receivable from Related Parties Collections Payments for Advance to Affiliate Advances Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Net cash provided by (used in) investing activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Cash flows from financing activities - Payments of Ordinary Dividends, Common Stock Dividends paid Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation [Abstract] Cash and cash equivalents - net change from: Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Operating, investing and financing activities Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Including Discontinued Operation Balance at end of period Balance at beginning of period Supplemental Cash Flow Information [Abstract] Supplemental disclosures - Noncash Investing and Financing Items [Abstract] Noncash investing activities - Amount of Increase (Decrease) in payables related to purchases of fixed assets that have occurred. Increase Decrease In Accruals For Capital Expenditure Change in accruals for capital expenditures Right-of-Use Asset Obtained in Exchange for Operating Lease Liability Right-of-use asset obtained in exchange for a lease liability Organization Consolidation And Presentation Of Financial Statements [Abstract] Basis of presentation and significant accounting policies. Basis Of Presentation And Significant Accounting Policies [Table] Basis Of Presentation And Significant Accounting Policies [Table] Basis of presentation and significant accounting policies. Basis Of Presentation And Significant Accounting Policies [Line Items] Organization and basis of presentation: Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization and basis of presentation Segment Reporting [Abstract] Schedule of Segment Reporting Information, by Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Segment Reporting Information [Line Items] Business segment information Segment Reporting Disclosure [Text Block] Business segment information Receivables [Abstract] Accounts and Financing Receivables [Table] Schedule Of Accounts Notes Loans And Financing Receivable [Table] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts receivable, net: Financing Receivables [Text Block] Accounts receivable, net Inventory Disclosure [Abstract] Inventory, Current [Table] Inventory Current [Table] Inventory [Line Items] Inventories, net: Inventory Disclosure [Text Block] Inventories, net Accounts payable and accrued liabilities [Abstract] Accounts payable and accrued liabilities. Accounts Payable And Accrued Liabilities [Table] Accounts Payable And Accrued Liabilities [Table] Accounts payable and accrued liabilities. Accounts Payable And Accrued Liabilities [Line Items] Accounts payable and accrued liabilities: Accounts Payable and Accrued Liabilities Disclosure [Text Block] Accounts payable and accrued liabilities Income taxes [Abstract] Income Tax Disclosure [Text Block] Income taxes Leases [Abstract] Lessee, Operating Leases [Text Block] Leases Commitments and Contingencies [Abstract] Loss Contingencies [Table] Loss Contingencies [Line Items] Commitments and contingencies: Commitments and Contingencies Disclosure [Text Block] Commitments and contingencies Financial instruments [Abstract] Fair Value, by Balance Sheet Grouping [Table] Fair Value By Balance Sheet Grouping [Table] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial instruments: Fair Value Disclosures [Text Block] Financial instruments Related party transactions [Abstract] Concentration Risk [Table] Concentration Risk [Line Items] Related party transactions: Related Party Transactions Disclosure [Text Block] Related party transactions Recent Accounting Pronouncements [Abstract] Accounting Standards Update and Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Recent accounting pronouncements: Accounting Standards Update and Change in Accounting Principle [Text Block] Recent Accounting Pronouncements Organization. Organization Policy [Text Block] Organization Basis of Accounting, Policy [Policy Text Block] Basis of presentation Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of Business Segment Information Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of Accounts Receivable, net Schedule of Inventory, Current [Table Text Block] Schedule of Inventories, net Schedule of Accounts Payable and Accrued Liabilities [Table Text Block] Schedule of Accounts Payable and Accrued Liabilities Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of Income taxes Fair Value, by Balance Sheet Grouping [Table Text Block] Schedule of Carrying Value and Estimated Fair Value of Financial Instruments Accounting Policies [Abstract] Legal Entity [Axis] Legal Entity All Entities [Member] Entity NL Industries. N L Industries [Member] NL Industries Valhi Inc. Valhi Inc [Member] Valhi Inc Contran Corporation. Contran Corporation [Member] Contran Corporation Ownership [Axis] Ownership Ownership [Domain] Ownership CompX International Inc. Comp X International Inc [Member] CompX International Inc Subsidiary, Ownership Percentage, Parent Percentage of ownership held by parent company Consolidation Items [Axis] Consolidation Items Consolidation Items [Domain] Consolidation Items Operating Segments [Member] Operating Segments Segment Reporting, Reconciling Item, Corporate Non-Segment [Member] Corporate Segments [Axis] Segments Segments [Domain] Segments Security products. Security Products [Member] Security Products Marine components. Marine Components Marine Components Disaggregation of Revenue [Abstract] Net sales: Operating Income (Loss) [Abstract] Operating income Number of reportable segments not disclosed. Number Of Reportable Segments Not Disclosed [Flag ] Number Of Reportable Segments Not Disclosed Accounts Receivable, before Allowance for Credit Loss, Current Accounts receivable, net Accounts Receivable, Allowance for Credit Loss, Current Allowance for doubtful accounts Inventory, Raw Materials, Net of Reserves Total raw materials Inventory, Work in Process, Net of Reserves Total work-in-process Inventory, Finished Goods, Net of Reserves Total finished goods Corporate Segment [Member] Corporate Accounts Payable, Current [Abstract] Accounts payable: Accounts Payable, Current Accounts payable Accrued Liabilities, Current [Abstract] Accrued liabilities: Employee-related Liabilities, Current Employee benefits Accrual for Taxes Other than Income Taxes, Current Taxes other than on income Accrued Professional Fees, Current Professional services Accrued Insurance, Current Insurance The amount of advances from customer classified as current. Advances from customers Advances from customers Accrued Utilities, Current Utilities Carrying value as of the balance sheet date of obligations incurred through that date and payable for customer tooling. Accrued Customer Tooling Cost Customer tooling Deferred Revenue, Current Deferred revenue Other Accrued Liabilities, Current Other Income Tax Expense (Benefit), Continuing Operations [Abstract] Income tax expenses Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount U.S. federal statutory tax rate Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount State income taxes, net of federal income tax rate Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Other, net Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent U.S. federal statutory rate (in Percent) Lessee, Operating Lease, Remaining Lease Term Remaining lease term of our operating lease Lessee, Operating Lease, Discount Rate Discount rate Measurement Basis [Axis] Portion at Fair Value Measurement [Member] Reported Value Measurement [Member] Carrying amount Estimate of Fair Value Measurement [Member] Fair value Cash and Cash Equivalents, Fair Value Disclosure Cash and cash equivalents Related Party Transaction [Table] Schedule Of Related Party Transactions By Related Party [Table] Long-Term Debt, Type [Axis] Long-term Debt, Type Long-Term Debt, Type [Domain] Long-term Debt, Type Unsecured Debt [Member] Unsecured Revolving Demand Promissory Related and Nonrelated Parties [Axis] Related Party Related and Nonrelated Parties [Domain] Related Party Related Party [Member] Related Party Counterparty Name [Axis] Counterparty Name [Domain] Related Party Transaction [Line Items] Related party transactions: Maximum lending capacity under the terms noted per the related party credit facility. Line Of Credit Facility Maximum Lending Capacity Maximum loan amount Loans Receivable, Basis Spread on Variable Rate Interest rate on loans repayment Loans receivable principal due on demand effective date. Loans Receivable Principal Due On Demand Effective Date Principal due on demand effective date