75000 - Document - Document and Entity Information link:presentationLink link:calculationLink link:definitionLink 75010 - Statement - Statements of Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75020 - Statement - Statement of Changes in Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75030 - Disclosure - Accounting Policies link:presentationLink link:calculationLink link:definitionLink 75040 - Disclosure - Description of the Plan link:presentationLink link:calculationLink link:definitionLink 75050 - Disclosure - Fair Value Measurements link:presentationLink link:calculationLink link:definitionLink 75060 - Disclosure - Income Tax Status link:presentationLink link:calculationLink link:definitionLink 75070 - Disclosure - Exempt Party-in-Interest Transactions link:presentationLink link:calculationLink link:definitionLink 75080 - Disclosure - Risks and Uncertainties link:presentationLink link:calculationLink link:definitionLink 75090 - Disclosure - Schedule of Assets (Held at End of Year) link:presentationLink link:calculationLink link:definitionLink 75100 - Disclosure - Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 75110 - Disclosure - Fair Value Measurements (Tables) link:presentationLink link:calculationLink link:definitionLink 75120 - Disclosure - Schedule of Assets (Held at End of Year) (Tables) link:presentationLink link:calculationLink link:definitionLink 75130 - Disclosure - Description of the Plan - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75140 - Disclosure - Fair Value Measurements - Schedule of Fair Value Hierarchy of Plan's Assets and Estimated Fair Value of Plan's Investment Funds (Details) link:presentationLink link:calculationLink link:definitionLink 75150 - Disclosure - Income Tax Status - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75160 - Disclosure - Exempt Party-in-Interest Transactions (Details) link:presentationLink link:calculationLink link:definitionLink 75170 - Disclosure - Schedule of Assets (Held at End of Year) (Details) link:presentationLink link:calculationLink link:definitionLink 75170 - Disclosure - Schedule of Assets (Held at End of Year) (Details) [Default] link:presentationLink link:calculationLink link:definitionLink BlackRock US Debt Index Fund M [Member] BlackRock US Debt Index Fund M. BlackRock US Debt Index Fund M EBP, Change in Net Asset Available for Benefit, Increase [Abstract] EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid to participants EBP 56-1848578 006 [Member] EBP 56-1848578 006. EBP 56-1848578 006 EBP, Trustee [Member] Employee Benefit Plan Trustee EBP, Receivable [Abstract] Receivables: Fair Value, Inputs, Level 2 [Member] Level 2 EBP, Related Party and Party-in-Interest Transactions [Line Items] Employee Benefit Plan, Related Party and Party-in-Interest Transactions [Line Items] Document Fiscal Period Focus EBP, Employer Contribution, Receivable Martin Marietta Materials, Inc. contributions EBP, Tax Status [Abstract] Employee benefit plan, notes receivable from participants reuters prime rate Employee Benefit Plan Notes Receivable From Participants Reuters Prime Rate Employee Benefit Plan Notes Receivable From Participants Reuters Prime Rate EBP, Description of Plan [Text Block] Description of the Plan Employee Benefit Plan Risk And Uncertainty Table Employee Benefit Plan Risk And Uncertainty Table EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Interest on notes receivable from participants Investment, Identifier [Axis] EBP, Change in Net Asset Available for Benefit, Decrease from Administrative Expense Administrative expenses Employee benefit plan, administrative expenses EBP, Description of Plan [Line Items] BlackRock Equity Index Fund J [Member] BlackRock Equity Index Fund J. BlackRock Equity Index Fund J EBP, Employer Contribution, Matching Percentage Employee benefit plan, employer contribution, matching percentage EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Investment, Fair Value and NAV [Abstract] EBP, Accounting Policy [Line Items] EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan Transfer from other plan due to merger Employee Benefit Plan Employer Contribution Participant Compensation Matched Percentage Second Basic Contribution Employee Benefit Plan Employer Contribution Participant Compensation Matched Percentage Second Basic Contribution Employee benefit plan employer contribution participant compensation matched percentage second basic contribution EBP, Schedule of Asset Held for Investment [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP 006 [Member] EBP 006. EBP 006 EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Employee benefit plan, note receivable from participant, account, maximum borrowing, amount Employee Benefit Plan Participant Contribution Automatic Deferral Rate Limit Percentage Employee Benefit Plan Participant Contribution Automatic Deferral Rate Limit Percentage Employee benefit plan participant contribution automatic deferral rate limit percentage Common Collective Trust [Member] Collective Trust Funds Amendment Flag Martin Marietta Materials, Inc. EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash Employee Benefit Plan, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash, Total EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] Deductions from net assets attributed to: EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount Employee benefit plan, note receivable from participant, account, minimum borrowing, amount EBP, Payment to Participant [Policy Text Block] Payments of Benefits Employee contributions Employee contributions EBP, Schedule of Asset Held for Investment [Line Items] Fair Value Hierarchy and NAV [Axis] EBP, Employer, Common Stock Fund [Member] Martin Marietta Materials, Inc. Common Stock EBP, Investment, Current Value, Type [Extensible Enumeration] Investment Type [Axis] Document Type Entity Central Index Key EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition EBP, Accounting Policy [Table] EBP, Basis of Accounting [Policy Text Block] Basis of Accounting Current Fiscal Year End Date EBP, Description of Plan [Table] EBP, Employer, Common Stock [Member] Common Stock EBP, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment Employee Benefit Plan, Change in Net Asset Available for Benefit, Increase from Interest and Dividend Income on Investment, Total Interest and dividend income Employee Benefit Plan Notes Receivable From Participants Primary Residence Loan Term Employee Benefit Plan Notes Receivable From Participants Primary Residence Loan Term Employee benefit plan, notes receivable from participants primary residence loan term EBP, Investment, Number of Shares Number of shares held Minimum [Member] Minimum EBP, Related Party and Party-in-Interest Transactions [Text Block] Exempt Party-in-Interest Transactions EBP, Change in Net Asset Available for Benefit, Increase from Contribution Total contributions EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] EBP, Expense [Policy Text Block] Administrative Expenses Employee Benefit Plan, Participant Contribution Adjustment Percentage Employee Benefit Plan, Participant Contribution Adjustment Percentage Employee benefit plan, participant contribution adjustment percentage Document Information [Line Items] Fair Value Measured at Net Asset Value Per Share [Member] Fair Value Measured at Net Asset Value Per Share EBP, Statement of Net Asset Available for Benefit [Abstract] EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Excluding Rollover Employees EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Contributions: Tax Determination Letter, Date Tax determination letter, date EBP, Participant Contribution, Automatic, Deferral Rate Employee benefit plan, participant contribution, automatic, deferral rate EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value Employee Benefit Plan, Investment, Excluding Plan Interest in Master Trust, Fair Value, Beginning Balance Investments at fair value Investments at fair value EBP, Use of Estimate [Policy Text Block] Use of Estimates Employee Benefit Plan Risk And Uncertainty LineItems Employee Benefit Plan Risk And Uncertainty [Line Items] Mutual Fund [Member] Mutual Funds Entity [Domain] Employee Benefit Plan Notes Receivable From Participants Personal LoanTerm Employee Benefit Plan Notes Receivable From Participants Personal LoanTerm Employee benefit plan, notes receivable from participants personal loan term EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Cost Employee benefit plan, investment acquired, excluding plan interest in master trust, cost BlackRock LifePath Portfolios Class O [Member] BlackRock LifePath Portfolios Class O. BlackRock LifePath Portfolios Class O EBP, Summary of Accounting Policy [Text Block] Accounting Policies Employee Benefit Plan, Participant Contribution Before and After tax Percentage of Base Pay Employee Benefit Plan, Participant Contribution Before and After tax Percentage of Base Pay Employee benefit plan, participant contribution before and after tax percentage of base pay Employee Benefit Plan Risk And Uncertainty Abstract Employee Benefit Plan Risk And Uncertainty Abstract EBP, Investment, Fair Value and NAV [Text Block] Fair Value Measurements EBP, Description of Plan and Accounting Change [Abstract] EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution EBP, Statement of Change in Net Asset Available for Benefit [Line Items] Statistical Measurement [Domain] BlackRock Mid Cap Equity Index Fund M [Member] BlackRock Mid Cap Equity Index Fund M. BlackRock Mid Cap Equity Index Fund M EBP, Note Receivable from Participant Notes receivable from participants Document Period End Date Fair Value Hierarchy and NAV [Domain] EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage Employee benefit plan, note receivable from participant, account, maximum borrowing, to total account, percentage Tax Determination Letter, Obtained Tax determination letter, obtained EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Subsequent Event [Policy Text Block] Subsequent Events Employee Benefit Plan Schedule Of Assets [Text Block] Employee Benefit Plan Schedule Of Assets [Text Block] Schedule of Assets EBP, Participant Contribution, Pretax, Maximum Annual Compensation, Amount Employee benefit plan, participant contribution, pretax, maximum annual compensation, amount Cover [Abstract] Investments [Domain] EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment [Abstract] Investment income: EBP, Net Asset Available for Benefit Net assets available for benefits Beginning of year End of year EBP, Investment, Fair Value and NAV [Table Text Block] Schedule of Fair Value Hierarchy of Plan's Assets and Estimated Fair Value of Plan's Investment Funds Employee Benefit Plan Employer Contribution Matching Percentage on Second Basic Contribution Employee Benefit Plan Employer Contribution Matching Percentage on Second Basic Contribution Employee benefit plan employer contribution matching percentage on second basic contribution EBP, Net Asset Available for Benefit [Abstract] Net assets available for benefits: EBP, Schedule of Asset Held for Investment [Abstract] Investments Measured at Net Asset Value [Member] Investments Measured at Net Asset Value. Investments Measured at Net Asset Value EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Employee benefit plan, asset held for investment, excluding plan interest in master trust, current value EBP, Note Receivable from Participant [Policy Text Block] Notes Receivable from Participants Schedule of Assets Schedule of Assets (Held at End of Year) EBP, Statement of Net Asset Available for Benefit [Table] Document Fiscal Year Focus EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment Employee Benefit Plan, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment, Total Net appreciation in fair value of investments EBP, Employer Contribution, Participant Compensation Matched, Percentage Employee benefit plan, employer contribution, participant compensation matched, percentage EBP, Statement of Change in Net Asset Available for Benefit [Table] EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Employee benefit plan, participant contribution, pretax, maximum annual compensation to total compensation, percentage EBP, Plan Number EBP, Investment, Fair Value and NAV [Line Items] Document Information [Table] Legal Entity [Axis] EBP, Asset [Abstract] EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Income (Loss) on Investment Investment income, Total Employee Benefit Plan Participant Contribution Annual Automatic Increase in Deferral Rate Employee Benefit Plan Participant Contribution Annual Automatic Increase in Deferral Rate Employee benefit plan participant contribution annual automatic increase in deferral rate EBP, Investment, Fair Value and NAV [Table] EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Rollover Rollovers BlackRock Russell 2000 Index Fund M [Member] BlackRock Russell 2000 Index Fund M. BlackRock Russell 2000 Index Fund M EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] EBP, Asset Held for Investment Employee Benefit Plan, Asset Held for Investment Galliard Stable Return Fund E [Member] Galliard Stable Return Fund E. Galliard Stable Return Fund E Income Tax Status Income Tax Status Maximum [Member] Maximum Statistical Measurement [Axis] EBP, Statement of Change in Net Asset Available for Benefit [Abstract] EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Employee benefit plan, change in net asset available for benefit, increase from dividend income on investment Entity Registrant Name EBP, Receivable Receivables, Total EBP, Asset Held for Investment, Participant Loan, Interest Rate Employee benefit plan, asset held for investment, participant loan, interest rate Employee Benefit Plan Redemption Notice Period Employee benefit plan redemption notice period. Redemption Notice Period Collective Trust Fund [Member] Collective trust fund. Collective Trust Fund EBP, Related Party and Party-in-Interest [Domain] EBP, Related Party and Party-in-Interest [Axis] Employee Benefit Plan, Participant Contribution After Tax Percentage of Base Pay Employee Benefit Plan, Participant Contribution After Tax Percentage of Base Pay Employee benefit plan, participant contribution after tax percentage of base pay EBP, Risk and Uncertainty [Text Block] Risks and Uncertainties EBP, Change in Net Asset Available for Benefit, Decrease Total deductions Fair Value, Inputs, Level 1 [Member] Level 1 Employee Benefit Plans Vesting Percentage Employee Benefit Plans Vesting Percentage Employee benefit plans vesting percentage Employee Benefit Plan Assets Transferred into the Plan Employee benefit plan assets transferred into the Plan. Employee benefit blan assets transferred into the Plan Harbor Capital Appreciation R [Member] Harbor Capital Appreciation R. Harbor Capital Appreciation R EBP, Tax Status [Line Items] Entity Tax Identification Number EBP, Asset Held for Investment, Participant Loan, Maturity Date Employee benefit plan, asset held for investment, participant loan, maturity date EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Net change EBP, Tax Status [Table] EBP, Asset Held for Investment, Party-in-Interest [true false] Washington Mutual. Galliard Capital Management LLC. Dodge & Cox Funds [Member] Dodge & Cox Funds. The Vanguard Group [Member] BlackRock Institutional Trust Company NA. Washington Mutual [Member] Harbor funds. The Vanguard Group. Fidelity Investments Inc. Harbor Funds [Member] Fidelity Investments Inc [Member] Martin Marietta Materials, Inc. Martin Marietta Materials, Inc [Member] IS MSCI EAFE INTL K. Great Gray Trust Company, LLC. BlackRock Institutional Trust Company N.A [Member] Great Gray Trust Company, LLC [Member] Galliard Capital Management LLC [Member] IS MSCI EAFE INTL K [Member]