<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.21.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>164</ContextCount>
  <ElementCount>293</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>51</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>100000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>100010 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>100020 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>100030 - Statement - Consolidated Statements of Earnings and Comprehensive Earnings (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedStatementsOfEarningsAndComprehensiveEarningsUnaudited</Role>
      <ShortName>Consolidated Statements of Earnings and Comprehensive Earnings (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>100040 - Statement - Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>100050 - Statement - Consolidated Statements of Total Equity (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedStatementsOfTotalEquityUnaudited</Role>
      <ShortName>Consolidated Statements of Total Equity (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>100060 - Statement - Consolidated Statements of Total Equity (Parenthetical) (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/StatementConsolidatedStatementsOfTotalEquityParentheticalUnaudited</Role>
      <ShortName>Consolidated Statements of Total Equity (Parenthetical) (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>100070 - Disclosure - Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPolicies</Role>
      <ShortName>Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>100080 - Disclosure - Revenue Recognition</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognition</Role>
      <ShortName>Revenue Recognition</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>100090 - Disclosure - Inventories, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureInventoriesNet</Role>
      <ShortName>Inventories, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>100100 - Disclosure - Long-Term Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebt</Role>
      <ShortName>Long-Term Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>100110 - Disclosure - Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureFinancialInstruments</Role>
      <ShortName>Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>100120 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>100130 - Disclosure - Pension and Postretirement Benefits</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosurePensionAndPostretirementBenefits</Role>
      <ShortName>Pension and Postretirement Benefits</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>100140 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>100150 - Disclosure - Business Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureBusinessSegments</Role>
      <ShortName>Business Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>100160 - Disclosure - Revenues and Gross Profit</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenuesAndGrossProfit</Role>
      <ShortName>Revenues and Gross Profit</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>100170 - Disclosure - Supplemental Cash Flow Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformation</Role>
      <ShortName>Supplemental Cash Flow Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>100180 - Disclosure - Other Operating (Income) and Expenses, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureOtherOperatingIncomeAndExpensesNet</Role>
      <ShortName>Other Operating (Income) and Expenses, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>100190 - Disclosure - Other Nonoperating (Income) and Expenses, Net</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureOtherNonoperatingIncomeAndExpensesNet</Role>
      <ShortName>Other Nonoperating (Income) and Expenses, Net</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>100200 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>100210 - Disclosure - Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPolicies</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>100220 - Disclosure - Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesTables</Role>
      <ShortName>Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPolicies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>100230 - Disclosure - Revenue Recognition (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognitionTables</Role>
      <ShortName>Revenue Recognition (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognition</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>100240 - Disclosure - Inventories, Net (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureInventoriesNetTables</Role>
      <ShortName>Inventories, Net (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureInventoriesNet</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>100250 - Disclosure - Long-Term Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebtTables</Role>
      <ShortName>Long-Term Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebt</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>100260 - Disclosure - Pension and Postretirement Benefits (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosurePensionAndPostretirementBenefitsTables</Role>
      <ShortName>Pension and Postretirement Benefits (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosurePensionAndPostretirementBenefits</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>100270 - Disclosure - Business Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureBusinessSegmentsTables</Role>
      <ShortName>Business Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureBusinessSegments</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>100280 - Disclosure - Revenues and Gross Profit (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenuesAndGrossProfitTables</Role>
      <ShortName>Revenues and Gross Profit (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenuesAndGrossProfit</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>100290 - Disclosure - Supplemental Cash Flow Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformationTables</Role>
      <ShortName>Supplemental Cash Flow Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformation</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>100300 - Disclosure - Significant Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Significant Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>100310 - Disclosure - Significant Accounting Policies - Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesComprehensiveEarningsAttributableToMartinMariettaMaterialsIncorporatedDetail</Role>
      <ShortName>Significant Accounting Policies - Comprehensive Earnings Attributable to Martin Marietta Materials Incorporated (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>100320 - Disclosure - Significant Accounting Policies - Changes in Accumulated Other Comprehensive Loss Net of Tax (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesChangesInAccumulatedOtherComprehensiveLossNetOfTaxDetail</Role>
      <ShortName>Significant Accounting Policies - Changes in Accumulated Other Comprehensive Loss Net of Tax (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>100330 - Disclosure - Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesNoncurrentDeferredTaxAssetsRecordedInAccumulatedOtherComprehensiveLossDetail</Role>
      <ShortName>Significant Accounting Policies - Noncurrent Deferred Tax Assets Recorded in Accumulated Other Comprehensive Loss (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>100340 - Disclosure - Significant Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Loss (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesReclassificationsOutOfAccumulatedOtherComprehensiveLossDetail</Role>
      <ShortName>Significant Accounting Policies - Reclassifications Out of Accumulated Other Comprehensive Loss (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>100350 - Disclosure - Significant Accounting Policies - Basic and Diluted Earnings Per Common Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesBasicAndDilutedEarningsPerCommonShareDetail</Role>
      <ShortName>Significant Accounting Policies - Basic and Diluted Earnings Per Common Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>100360 - Disclosure - Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSignificantAccountingPoliciesReconciliationOfCashCashEquivalentsAndRestrictedCashDetail</Role>
      <ShortName>Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>100370 - Disclosure - Revenue Recognition - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognitionAdditionalInformationDetail</Role>
      <ShortName>Revenue Recognition - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>100380 - Disclosure - Revenue Recognition - Additional Information (Detail 1)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognitionAdditionalInformationDetail1</Role>
      <ShortName>Revenue Recognition - Additional Information (Detail 1)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>100390 - Disclosure - Revenue Recognition - Schedule of Company's Total Revenues by Category for each Reportable Segment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognitionScheduleOfCompanySTotalRevenuesByCategoryForEachReportableSegmentDetail</Role>
      <ShortName>Revenue Recognition - Schedule of Company's Total Revenues by Category for each Reportable Segment (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>100400 - Disclosure - Revenue Recognition - Summary of Information About the Company's Contract Balances (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenueRecognitionSummaryOfInformationAboutCompanySContractBalancesDetail</Role>
      <ShortName>Revenue Recognition - Summary of Information About the Company's Contract Balances (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>100410 - Disclosure - Inventories, Net - Schedule of Inventories Net (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureInventoriesNetScheduleOfInventoriesNetDetail</Role>
      <ShortName>Inventories, Net - Schedule of Inventories Net (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>100420 - Disclosure - Long-Term Debt - Long-Term Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebtLongTermDebtDetail</Role>
      <ShortName>Long-Term Debt - Long-Term Debt (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>100430 - Disclosure - Long-Term Debt - Long-Term Debt (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebtLongTermDebtParentheticalDetail</Role>
      <ShortName>Long-Term Debt - Long-Term Debt (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>100440 - Disclosure - Long-Term Debt - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureLongTermDebtAdditionalInformationDetail</Role>
      <ShortName>Long-Term Debt - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>100450 - Disclosure - Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureFinancialInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Financial Instruments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>100460 - Disclosure - Income Taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>Income Taxes - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>100470 - Disclosure - Pension and Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Credit) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosurePensionAndPostretirementBenefitsScheduleOfComponentsOfNetPeriodicBenefitCostCreditDetail</Role>
      <ShortName>Pension and Postretirement Benefits - Schedule of Components of Net Periodic Benefit Cost (Credit) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>100480 - Disclosure - Commitments and Contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureCommitmentsAndContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and Contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>100490 - Disclosure - Business Segments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureBusinessSegmentsAdditionalInformationDetail</Role>
      <ShortName>Business Segments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>100500 - Disclosure - Business Segments - Financial Data for Continuing Operations for Company's Reportable Business Segments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureBusinessSegmentsFinancialDataForContinuingOperationsForCompanySReportableBusinessSegmentsDetail</Role>
      <ShortName>Business Segments - Financial Data for Continuing Operations for Company's Reportable Business Segments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>100510 - Disclosure - Revenues and Gross Profit - Total Revenues and Gross Profit by Product Line (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureRevenuesAndGrossProfitTotalRevenuesAndGrossProfitByProductLineDetail</Role>
      <ShortName>Revenues and Gross Profit - Total Revenues and Gross Profit by Product Line (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>100520 - Disclosure - Supplemental Cash Flow Information - Schedule Of Noncash Investing and Financing Activities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformationScheduleOfNoncashInvestingAndFinancingActivitiesDetail</Role>
      <ShortName>Supplemental Cash Flow Information - Schedule Of Noncash Investing and Financing Activities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>100530 - Disclosure - Supplemental Cash Flow Information - Supplemental Disclosures of Cash Flow Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformationSupplementalDisclosuresOfCashFlowInformationDetail</Role>
      <ShortName>Supplemental Cash Flow Information - Supplemental Disclosures of Cash Flow Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>100540 - Disclosure - Supplemental Cash Flow Information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureSupplementalCashFlowInformationAdditionalInformationDetail</Role>
      <ShortName>Supplemental Cash Flow Information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="mlm-10q_20210331.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>100550 - Disclosure - Other Nonoperating (Income) and Expenses, Net - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://martinmarietta.com/20210331/taxonomy/role/DisclosureOtherNonoperatingIncomeAndExpensesNetAdditionalInformationDetail</Role>
      <ShortName>Other Nonoperating (Income) and Expenses, Net - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://martinmarietta.com/20210331/taxonomy/role/DisclosureOtherNonoperatingIncomeAndExpensesNet</ParentRole>
      <Position>56</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File doctype="10-Q" original="mlm-10q_20210331.htm">mlm-10q_20210331.htm</File>
    <File>mlm-20210331.xsd</File>
    <File>mlm-20210331_cal.xml</File>
    <File>mlm-20210331_def.xml</File>
    <File>mlm-20210331_lab.xml</File>
    <File>mlm-20210331_pre.xml</File>
    <File>mlm-ex3101_10.htm</File>
    <File>mlm-ex3102_7.htm</File>
    <File>mlm-ex3201_6.htm</File>
    <File>mlm-ex3202_8.htm</File>
    <File>mlm-ex95_9.htm</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies>
    <BaseTaxonomy>http://xbrl.sec.gov/dei/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/us-gaap/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://fasb.org/srt/2020-01-31</BaseTaxonomy>
    <BaseTaxonomy>http://xbrl.sec.gov/stpr/2018-01-31</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
