<?xml version='1.0' encoding='UTF-8'?>
<FilingSummary>
  <Version>3.7.0.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>169</ContextCount>
  <ElementCount>258</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>73</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>8</UnitCount>
  <MyReports>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0001000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1001000 - Statement - Condensed Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CondensedConsolidatedBalanceSheets</Role>
      <ShortName>Condensed Consolidated Balance Sheets</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1001501 - Statement - Condensed Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>Condensed Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1002000 - Statement - Condensed Consolidated Statements of Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CondensedConsolidatedStatementsOfIncomeUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1003000 - Statement - Condensed Consolidated Statements of Comprehensive Income (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CondensedConsolidatedStatementsOfComprehensiveIncomeUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Comprehensive Income (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1006000 - Statement - Condensed Consolidated Statements of Cash Flows (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>Condensed Consolidated Statements of Cash Flows (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>2101100 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Basis of Presentation and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>2102100 - Disclosure - Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Acquisitions</Role>
      <ShortName>Acquisitions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Divestitures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Divestitures</Role>
      <ShortName>Divestitures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>2103100 - Disclosure - Restructuring Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/RestructuringExpenses</Role>
      <ShortName>Restructuring Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>2104100 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/FairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Goodwill</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Goodwill</Role>
      <ShortName>Goodwill</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>2105100 - Disclosure - Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/IntangibleAssets</Role>
      <ShortName>Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>2107100 - Disclosure - Property, Plant and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/PropertyPlantAndEquipment</Role>
      <ShortName>Property, Plant and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>2112100 - Disclosure - Derivative Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DerivativeInstruments</Role>
      <ShortName>Derivative Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>2113100 - Disclosure - Debt</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Debt</Role>
      <ShortName>Debt</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>2115100 - Disclosure - Accumulated Other Comprehensive Income (Loss)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AccumulatedOtherComprehensiveIncomeLoss</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>2121100 - Disclosure - Earnings Per Share (EPS)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/EarningsPerShareEps</Role>
      <ShortName>Earnings Per Share (EPS)</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>2128100 - Disclosure - Supplementary Cash Flow Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/SupplementaryCashFlowInformation</Role>
      <ShortName>Supplementary Cash Flow Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>2129100 - Disclosure - Business Segments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BusinessSegments</Role>
      <ShortName>Business Segments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>2130100 - Disclosure - Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Contingencies</Role>
      <ShortName>Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>2131100 - Disclosure - Commitments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/Commitments</Role>
      <ShortName>Commitments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>2201201 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Basis of Presentation and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>2301302 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Basis of Presentation and Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>24</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2302301 - Disclosure - Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AcquisitionsTables</Role>
      <ShortName>Acquisitions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Acquisitions</ParentRole>
      <Position>25</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>2303301 - Disclosure - Restructuring Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/RestructuringExpensesTables</Role>
      <ShortName>Restructuring Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/RestructuringExpenses</ParentRole>
      <Position>26</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>2304301 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/FairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/FairValueMeasurements</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Goodwill (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/GoodwillTables</Role>
      <ShortName>Goodwill (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Goodwill</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>2305301 - Disclosure - Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/IntangibleAssetsTables</Role>
      <ShortName>Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/IntangibleAssets</ParentRole>
      <Position>29</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>2307301 - Disclosure - Property, Plant and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/PropertyPlantAndEquipmentTables</Role>
      <ShortName>Property, Plant and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/PropertyPlantAndEquipment</ParentRole>
      <Position>30</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>2312301 - Disclosure - Derivative Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DerivativeInstrumentsTables</Role>
      <ShortName>Derivative Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/DerivativeInstruments</ParentRole>
      <Position>31</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>2313301 - Disclosure - Debt (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DebtTables</Role>
      <ShortName>Debt (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Debt</ParentRole>
      <Position>32</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>2315301 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AccumulatedOtherComprehensiveIncomeLossTables</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AccumulatedOtherComprehensiveIncomeLoss</ParentRole>
      <Position>33</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>2321301 - Disclosure - Earnings Per Share (EPS) (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/EarningsPerShareEpsTables</Role>
      <ShortName>Earnings Per Share (EPS) (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/EarningsPerShareEps</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>2328301 - Disclosure - Supplementary Cash Flow Information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/SupplementaryCashFlowInformationTables</Role>
      <ShortName>Supplementary Cash Flow Information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/SupplementaryCashFlowInformation</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>2329301 - Disclosure - Business Segments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BusinessSegmentsTables</Role>
      <ShortName>Business Segments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BusinessSegments</ParentRole>
      <Position>36</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>2401403 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Additional Information) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Basis of Presentation and Summary of Significant Accounting Policies (Additional Information) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>37</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>2401404 - Disclosure - Basis of Presentation and Summary of Significant Accounting Policies (Changes in estimates on contracts) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesChangesInEstimatesOnContractsDetails</Role>
      <ShortName>Basis of Presentation and Summary of Significant Accounting Policies (Changes in estimates on contracts) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>38</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>2402402 - Disclosure - Acquisitions (Textual) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AcquisitionsTextualDetails</Role>
      <ShortName>Acquisitions (Textual) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AcquisitionsTables</ParentRole>
      <Position>39</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>2402403 - Disclosure - Acquisitions (Purchase price) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AcquisitionsPurchasePriceDetails</Role>
      <ShortName>Acquisitions (Purchase price) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AcquisitionsTables</ParentRole>
      <Position>40</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>2402404 - Disclosure - Acquisitions (Integration Costs) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AcquisitionsIntegrationCostsDetails</Role>
      <ShortName>Acquisitions (Integration Costs) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AcquisitionsTables</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>2402405 - Disclosure - Acquisitions (Pro Forma Information) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AcquisitionsProFormaInformationDetails</Role>
      <ShortName>Acquisitions (Pro Forma Information) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AcquisitionsTables</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>2403401 - Disclosure - Divestitures (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DivestituresNarrativeDetails</Role>
      <ShortName>Divestitures (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Divestitures</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>2403402 - Disclosure - Restructuring Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/RestructuringExpensesDetails</Role>
      <ShortName>Restructuring Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/RestructuringExpensesTables</ParentRole>
      <Position>44</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>2404402 - Disclosure - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/FairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/FairValueMeasurementsTables</ParentRole>
      <Position>45</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Goodwill (Schedule of Changes in Goodwill by Segment) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/GoodwillScheduleOfChangesInGoodwillBySegmentDetail</Role>
      <ShortName>Goodwill (Schedule of Changes in Goodwill by Segment) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/GoodwillTables</ParentRole>
      <Position>46</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>2405402 - Disclosure - Intangible Assets (Summary) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/IntangibleAssetsSummaryDetails</Role>
      <ShortName>Intangible Assets (Summary) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/IntangibleAssetsTables</ParentRole>
      <Position>47</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>2405403 - Disclosure - Intangible Assets (Amortization of Intangibles) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/IntangibleAssetsAmortizationOfIntangiblesDetails</Role>
      <ShortName>Intangible Assets (Amortization of Intangibles) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/IntangibleAssetsTables</ParentRole>
      <Position>48</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>2405404 - Disclosure - Intangible Assets (Narrative) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/IntangibleAssetsNarrativeDetails</Role>
      <ShortName>Intangible Assets (Narrative) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/IntangibleAssetsTables</ParentRole>
      <Position>49</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>2407402 - Disclosure - Property, Plant and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/PropertyPlantAndEquipmentDetails</Role>
      <ShortName>Property, Plant and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/PropertyPlantAndEquipmentTables</ParentRole>
      <Position>50</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>2412402 - Disclosure - Derivative Instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DerivativeInstrumentsDetails</Role>
      <ShortName>Derivative Instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/DerivativeInstrumentsTables</ParentRole>
      <Position>51</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>2413402 - Disclosure - Debt (Summary of debt) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DebtSummaryOfDebtDetail</Role>
      <ShortName>Debt (Summary of debt) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/DebtTables</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>2413403 - Disclosure - Debt (Senior Secured Notes and Senoir Secured Term Loans) (Detail)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.leidos.com/role/DebtSeniorSecuredNotesAndSenoirSecuredTermLoansDetail</Role>
      <ShortName>Debt (Senior Secured Notes and Senoir Secured Term Loans) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/DebtTables</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>2413404 - Disclosure - Debt (Revolving Credit Facility) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/DebtRevolvingCreditFacilityDetail</Role>
      <ShortName>Debt (Revolving Credit Facility) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/DebtTables</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>2415402 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Loss) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/AccumulatedOtherComprehensiveIncomeLossScheduleOfAccumulatedOtherComprehensiveLossDetail</Role>
      <ShortName>Accumulated Other Comprehensive Income (Loss) (Schedule of Accumulated Other Comprehensive Loss) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/AccumulatedOtherComprehensiveIncomeLossTables</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>2421402 - Disclosure - Earnings Per Share (EPS) (Reconciliation of Weighted Average Number of Shares Outstanding) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/EarningsPerShareEpsReconciliationOfWeightedAverageNumberOfSharesOutstandingDetail</Role>
      <ShortName>Earnings Per Share (EPS) (Reconciliation of Weighted Average Number of Shares Outstanding) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/EarningsPerShareEpsTables</ParentRole>
      <Position>56</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>2421403 - Disclosure - Earnings Per Share (EPS) (Schedule of Stock-Based Awards Excluded from Weighted Average Shares Outstanding) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/EarningsPerShareEpsScheduleOfStockBasedAwardsExcludedFromWeightedAverageSharesOutstandingDetail</Role>
      <ShortName>Earnings Per Share (EPS) (Schedule of Stock-Based Awards Excluded from Weighted Average Shares Outstanding) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/EarningsPerShareEpsTables</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>2428402 - Disclosure - Supplementary Cash Flow Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/SupplementaryCashFlowInformationDetail</Role>
      <ShortName>Supplementary Cash Flow Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/SupplementaryCashFlowInformationTables</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>2429402 - Disclosure - Business Segments (Schedule of Segment Reporting Information by Segment) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/BusinessSegmentsScheduleOfSegmentReportingInformationBySegmentDetail</Role>
      <ShortName>Business Segments (Schedule of Segment Reporting Information by Segment) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/BusinessSegmentsTables</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>2430401 - Disclosure - Contingencies (Additional Information) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/ContingenciesAdditionalInformationDetail</Role>
      <ShortName>Contingencies (Additional Information) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Contingencies</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="ldos-20170331.xml">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>2431401 - Disclosure - Commitments (Additional Information) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.leidos.com/role/CommitmentsAdditionalInformationDetail</Role>
      <ShortName>Commitments (Additional Information) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.leidos.com/role/Commitments</ParentRole>
      <Position>61</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>ldos-20170331.xml</File>
    <File>ldos-20170331.xsd</File>
    <File>ldos-20170331_cal.xml</File>
    <File>ldos-20170331_def.xml</File>
    <File>ldos-20170331_lab.xml</File>
    <File>ldos-20170331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles/>
  <BaseTaxonomies/>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
