<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.26.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>1495</ContextCount>
  <ElementCount>1111</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>true</FootnotesReported>
  <SegmentCount>460</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>9</UnitCount>
  <MyReports>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>1001 - Document - Cover Page</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CoverPage</Role>
      <ShortName>Cover Page</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1002 - Statement - Consolidated income statement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedIncomeStatement</Role>
      <ShortName>Consolidated income statement</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1003 - Statement - Consolidated statement of comprehensive income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfComprehensiveIncome</Role>
      <ShortName>Consolidated statement of comprehensive income</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1004 - Statement - Consolidated statement of financial position</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfFinancialPosition</Role>
      <ShortName>Consolidated statement of financial position</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1005 - Statement - Consolidated statement of cash flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfCashFlows</Role>
      <ShortName>Consolidated statement of cash flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1006 - Statement - Consolidated statement of cash flows (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfCashFlowsParenthetical</Role>
      <ShortName>Consolidated statement of cash flows (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1007 - Statement - Consolidated statement of changes in shareholders' equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfChangesInShareholdersEquity</Role>
      <ShortName>Consolidated statement of changes in shareholders' equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1008 - Statement - Consolidated statement of changes in shareholders' equity (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedStatementOfChangesInShareholdersEquityParenthetical</Role>
      <ShortName>Consolidated statement of changes in shareholders' equity (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>995447 - Disclosure - Insider Trading Policies and Procedures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc</Role>
      <ShortName>Insider Trading Policies and Procedures</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>995550 - Disclosure - Cybersecurity Risk Management and Strategy Disclosure</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://xbrl.sec.gov/cyd/role/CybersecurityRiskManagementAndStrategyDisclosure</Role>
      <ShortName>Cybersecurity Risk Management and Strategy Disclosure</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>999001 - Disclosure - Corporate information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CorporateInformation</Role>
      <ShortName>Corporate information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>999002 - Disclosure - Summary Of Material Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPolicies</Role>
      <ShortName>Summary Of Material Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>999003 - Disclosure - Significant Changes In The Current Reporting Period</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SignificantChangesInTheCurrentReportingPeriod</Role>
      <ShortName>Significant Changes In The Current Reporting Period</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>999004 - Disclosure - Business combinations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinations</Role>
      <ShortName>Business combinations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>999005 - Disclosure - Revenue From Contracts With Customers</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomers</Role>
      <ShortName>Revenue From Contracts With Customers</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>999006 - Disclosure - Operating expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OperatingExpenses</Role>
      <ShortName>Operating expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>999007 - Disclosure - Audit and assurance services fees</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AuditAndAssuranceServicesFees</Role>
      <ShortName>Audit and assurance services fees</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>999008 - Disclosure - Finance income and costs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinanceIncomeAndCosts</Role>
      <ShortName>Finance income and costs</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>999009 - Disclosure - Other non-operating income / expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherNonOperatingIncomeExpenses</Role>
      <ShortName>Other non-operating income / expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>19</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>999010 - Disclosure - Income taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IncomeTaxes</Role>
      <ShortName>Income taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>20</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>999011 - Disclosure - Deferred tax balances</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DeferredTaxBalances</Role>
      <ShortName>Deferred tax balances</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>21</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>999012 - Disclosure - Components of other comprehensive income</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ComponentsOfOtherComprehensiveIncome</Role>
      <ShortName>Components of other comprehensive income</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>22</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>999013 - Disclosure - Earnings per share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShare</Role>
      <ShortName>Earnings per share</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>23</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>999014 - Disclosure - Dividends paid and proposed</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposed</Role>
      <ShortName>Dividends paid and proposed</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>999015 - Disclosure - Property, Plant and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipment</Role>
      <ShortName>Property, Plant and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>999016 - Disclosure - Assets in the course of construction</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsInTheCourseOfConstruction</Role>
      <ShortName>Assets in the course of construction</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>999017 - Disclosure - Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IntangibleAssets</Role>
      <ShortName>Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>27</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>999018 - Disclosure - Other financial assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherFinancialAssets</Role>
      <ShortName>Other financial assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>28</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>999019 - Disclosure - Investments accounted for using equity method</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethod</Role>
      <ShortName>Investments accounted for using equity method</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>999020 - Disclosure - Inventories</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/Inventories</Role>
      <ShortName>Inventories</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>999021 - Disclosure - Assets and liabilities related to contracts with customers</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsAndLiabilitiesRelatedToContractsWithCustomers</Role>
      <ShortName>Assets and liabilities related to contracts with customers</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>999022 - Disclosure - Trade And Other Receivables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherReceivables</Role>
      <ShortName>Trade And Other Receivables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>999023 - Disclosure - Financial Instruments</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstruments</Role>
      <ShortName>Financial Instruments</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>999024 - Disclosure - Financial risk management objectives and policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPolicies</Role>
      <ShortName>Financial risk management objectives and policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>34</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>999025 - Disclosure - Cash and cash equivalents</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashAndCashEquivalents</Role>
      <ShortName>Cash and cash equivalents</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>35</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>999026 - Disclosure - Shareholders' equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareholdersEquity</Role>
      <ShortName>Shareholders' equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>999027 - Disclosure - Non-controlling Interests</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/NonControllingInterests</Role>
      <ShortName>Non-controlling Interests</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>999028 - Disclosure - Share-Based Compensation Plans</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlans</Role>
      <ShortName>Share-Based Compensation Plans</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>999029 - Disclosure - Borrowings</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/Borrowings</Role>
      <ShortName>Borrowings</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>999030 - Disclosure - Provisions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/Provisions</Role>
      <ShortName>Provisions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>999031 - Disclosure - Trade and other payables</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherPayables</Role>
      <ShortName>Trade and other payables</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>41</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>999032 - Disclosure - Other long-term liabilities</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherLongTermLiabilities</Role>
      <ShortName>Other long-term liabilities</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>42</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>999033 - Disclosure - Employee benefit obligations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligations</Role>
      <ShortName>Employee benefit obligations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>43</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>999034 - Disclosure - Fixed Assets Suppliers</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FixedAssetsSuppliers</Role>
      <ShortName>Fixed Assets Suppliers</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>999035 - Disclosure - Commitments and contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CommitmentsAndContingencies</Role>
      <ShortName>Commitments and contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>999036 - Disclosure - Leases</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/Leases</Role>
      <ShortName>Leases</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>999037 - Disclosure - Cash flow information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashFlowInformation</Role>
      <ShortName>Cash flow information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>999038 - Disclosure - Related parties</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RelatedParties</Role>
      <ShortName>Related parties</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>999039 - Disclosure - C-band repurposing</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CBandRepurposing</Role>
      <ShortName>C-band repurposing</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>999040 - Disclosure - Subsequent events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SubsequentEvents</Role>
      <ShortName>Subsequent events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>999041 - Disclosure - Consolidated subsidiaries, associates</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedSubsidiariesAssociates</Role>
      <ShortName>Consolidated subsidiaries, associates</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>999042 - Disclosure - Summary Of Material Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPoliciesPolicies</Role>
      <ShortName>Summary Of Material Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.ses.com/role/SummaryOfMaterialAccountingPolicies</ParentRole>
      <Position>52</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>999043 - Disclosure - Summary Of Material Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPoliciesTables</Role>
      <ShortName>Summary Of Material Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/SummaryOfMaterialAccountingPolicies</ParentRole>
      <Position>53</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>999044 - Disclosure - Business combinations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinationsTables</Role>
      <ShortName>Business combinations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/BusinessCombinations</ParentRole>
      <Position>54</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>999045 - Disclosure - Revenue From Contracts With Customers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomersTables</Role>
      <ShortName>Revenue From Contracts With Customers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/RevenueFromContractsWithCustomers</ParentRole>
      <Position>55</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>999046 - Disclosure - Operating Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OperatingExpensesTables</Role>
      <ShortName>Operating Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>999047 - Disclosure - Audit and assurance services fees (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AuditAndAssuranceServicesFeesTables</Role>
      <ShortName>Audit and assurance services fees (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/AuditAndAssuranceServicesFees</ParentRole>
      <Position>57</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>999048 - Disclosure - Finance income and costs (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinanceIncomeAndCostsTables</Role>
      <ShortName>Finance income and costs (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/FinanceIncomeAndCosts</ParentRole>
      <Position>58</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>999049 - Disclosure - Other non-operating income / expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherNonOperatingIncomeExpensesTables</Role>
      <ShortName>Other non-operating income / expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/OtherNonOperatingIncomeExpenses</ParentRole>
      <Position>59</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>999050 - Disclosure - Income taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IncomeTaxesTables</Role>
      <ShortName>Income taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/IncomeTaxes</ParentRole>
      <Position>60</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>999051 - Disclosure - Deferred tax balances (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DeferredTaxBalancesTables</Role>
      <ShortName>Deferred tax balances (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/DeferredTaxBalances</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>999052 - Disclosure - Components of other comprehensive income (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ComponentsOfOtherComprehensiveIncomeTables</Role>
      <ShortName>Components of other comprehensive income (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/ComponentsOfOtherComprehensiveIncome</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>999053 - Disclosure - Earnings per share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareTables</Role>
      <ShortName>Earnings per share (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/EarningsPerShare</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>999054 - Disclosure - Dividends Paid and Proposed (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedTables</Role>
      <ShortName>Dividends Paid and Proposed (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>64</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>999055 - Disclosure - Property, Plant and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipmentTables</Role>
      <ShortName>Property, Plant and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/PropertyPlantAndEquipment</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>999056 - Disclosure - Assets in the course of construction (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsInTheCourseOfConstructionTables</Role>
      <ShortName>Assets in the course of construction (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/AssetsInTheCourseOfConstruction</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>999057 - Disclosure - Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IntangibleAssetsTables</Role>
      <ShortName>Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/IntangibleAssets</ParentRole>
      <Position>67</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>999058 - Disclosure - Other financial assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherFinancialAssetsTables</Role>
      <ShortName>Other financial assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/OtherFinancialAssets</ParentRole>
      <Position>68</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>999059 - Disclosure - Investments accounted for using equity method (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethodTables</Role>
      <ShortName>Investments accounted for using equity method (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethod</ParentRole>
      <Position>69</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>999060 - Disclosure - Inventories (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InventoriesTables</Role>
      <ShortName>Inventories (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/Inventories</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>999061 - Disclosure - Assets and liabilities related to contracts with customers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsAndLiabilitiesRelatedToContractsWithCustomersTables</Role>
      <ShortName>Assets and liabilities related to contracts with customers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/AssetsAndLiabilitiesRelatedToContractsWithCustomers</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>999062 - Disclosure - Trade And Other Receivables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherReceivablesTables</Role>
      <ShortName>Trade And Other Receivables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/TradeAndOtherReceivables</ParentRole>
      <Position>72</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>999063 - Disclosure - Financial Instruments (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsTables</Role>
      <ShortName>Financial Instruments (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/FinancialInstruments</ParentRole>
      <Position>73</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>999064 - Disclosure - Financial risk management objectives and policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesTables</Role>
      <ShortName>Financial risk management objectives and policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPolicies</ParentRole>
      <Position>74</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>999065 - Disclosure - Cash and cash equivalents (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashAndCashEquivalentsTables</Role>
      <ShortName>Cash and cash equivalents (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/CashAndCashEquivalents</ParentRole>
      <Position>75</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>999066 - Disclosure - Shareholders' equity (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareholdersEquityTables</Role>
      <ShortName>Shareholders' equity (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/ShareholdersEquity</ParentRole>
      <Position>76</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>999067 - Disclosure - Non-controlling interests (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/NonControllingInterestsTables</Role>
      <ShortName>Non-controlling interests (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <Position>77</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>999068 - Disclosure - Share-Based Compensation Plans (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansTables</Role>
      <ShortName>Share-Based Compensation Plans (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/ShareBasedCompensationPlans</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>999069 - Disclosure - Borrowings (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BorrowingsTables</Role>
      <ShortName>Borrowings (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/Borrowings</ParentRole>
      <Position>79</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>999070 - Disclosure - Provisions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ProvisionsTables</Role>
      <ShortName>Provisions (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/Provisions</ParentRole>
      <Position>80</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>999071 - Disclosure - Trade and other payables (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherPayablesTables</Role>
      <ShortName>Trade and other payables (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/TradeAndOtherPayables</ParentRole>
      <Position>81</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>999072 - Disclosure - Other long-term liabilities (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherLongTermLiabilitiesTables</Role>
      <ShortName>Other long-term liabilities (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/OtherLongTermLiabilities</ParentRole>
      <Position>82</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>999073 - Disclosure - Employee benefit obligations (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsTables</Role>
      <ShortName>Employee benefit obligations (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/EmployeeBenefitObligations</ParentRole>
      <Position>83</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>999074 - Disclosure - Fixed Assets Suppliers (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FixedAssetsSuppliersTables</Role>
      <ShortName>Fixed Assets Suppliers (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/FixedAssetsSuppliers</ParentRole>
      <Position>84</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>999075 - Disclosure - Commitments and contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/CommitmentsAndContingencies</ParentRole>
      <Position>85</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>999076 - Disclosure - Leases (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesTables</Role>
      <ShortName>Leases (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/Leases</ParentRole>
      <Position>86</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>999077 - Disclosure - Cash flow information (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashFlowInformationTables</Role>
      <ShortName>Cash flow information (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/CashFlowInformation</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>999078 - Disclosure - Related parties (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RelatedPartiesTables</Role>
      <ShortName>Related parties (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/RelatedParties</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>999079 - Disclosure - C-band repurposing (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CBandRepurposingTables</Role>
      <ShortName>C-band repurposing (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/CBandRepurposing</ParentRole>
      <Position>89</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>999080 - Disclosure - Consolidated subsidiaries, associates (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedSubsidiariesAssociatesTables</Role>
      <ShortName>Consolidated subsidiaries, associates (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.ses.com/role/ConsolidatedSubsidiariesAssociates</ParentRole>
      <Position>90</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>999081 - Disclosure - Corporate information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CorporateInformationAdditionalInformationDetail</Role>
      <ShortName>Corporate information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>999082 - Disclosure - Summary Of Material Accounting Policies - Summary Of US Dollar Exchange Rates Used By The Group (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPoliciesSummaryOfUsDollarExchangeRatesUsedByTheGroupDetail</Role>
      <ShortName>Summary Of Material Accounting Policies - Summary Of US Dollar Exchange Rates Used By The Group (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>999083 - Disclosure - Summary Of Material Accounting Policies - Summary Of Property, Plant And Equipment Is Depreciated Using The Straight-line Method (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPoliciesSummaryOfPropertyPlantAndEquipmentIsDepreciatedUsingTheStraightLineMethodDetail</Role>
      <ShortName>Summary Of Material Accounting Policies - Summary Of Property, Plant And Equipment Is Depreciated Using The Straight-line Method (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>999084 - Disclosure - Summary Of Material Accounting Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SummaryOfMaterialAccountingPoliciesAdditionalInformationDetail</Role>
      <ShortName>Summary Of Material Accounting Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>999085 - Disclosure - Significant Developments In The Current Reporting Period - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SignificantDevelopmentsInTheCurrentReportingPeriodAdditionalInformationDetail</Role>
      <ShortName>Significant Developments In The Current Reporting Period - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>999086 - Disclosure - Business Combinations - Summary Of detailed information about business combination (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinationsSummaryOfDetailedInformationAboutBusinessCombinationDetail</Role>
      <ShortName>Business Combinations - Summary Of detailed information about business combination (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>999087 - Disclosure - Business Combinations - Summary Of Assets And Liabilities Recognised As Of The Acquisition Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinationsSummaryOfAssetsAndLiabilitiesRecognisedAsOfTheAcquisitionExplanatoryDetail</Role>
      <ShortName>Business Combinations - Summary Of Assets And Liabilities Recognised As Of The Acquisition Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>999088 - Disclosure - Business Combinations - Summary Of Purchase Consideration Cash Outflow (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinationsSummaryOfPurchaseConsiderationCashOutflowDetail</Role>
      <ShortName>Business Combinations - Summary Of Purchase Consideration Cash Outflow (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>999089 - Disclosure - Business combinations  - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BusinessCombinationsAdditionalInformationDetail</Role>
      <ShortName>Business combinations  - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>999090 - Disclosure - Revenue From Contracts With Customers - Schedule of Revenue Allocated to the Relevant Business Unit (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomersScheduleOfRevenueAllocatedToTheRelevantBusinessUnitDetail</Role>
      <ShortName>Revenue From Contracts With Customers - Schedule of Revenue Allocated to the Relevant Business Unit (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>999091 - Disclosure - Revenue From Contracts With Customers - Schedule of Group's Revenue Analysis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomersScheduleOfGroupSRevenueAnalysisDetail</Role>
      <ShortName>Revenue From Contracts With Customers - Schedule of Group's Revenue Analysis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>101</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>999092 - Disclosure - Revenue From Contracts With Customers - Schedule of Group's Revenue from External Customers (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomersScheduleOfGroupSRevenueFromExternalCustomersDetail</Role>
      <ShortName>Revenue From Contracts With Customers - Schedule of Group's Revenue from External Customers (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>102</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>999093 - Disclosure - Revenue From Contracts With Customers - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RevenueFromContractsWithCustomersAdditionalInformationDetail</Role>
      <ShortName>Revenue From Contracts With Customers - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>103</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>999094 - Disclosure - Operating Expenses - Schedule of Components of Cost of Sales (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OperatingExpensesScheduleOfComponentsOfCostOfSalesDetail</Role>
      <ShortName>Operating Expenses - Schedule of Components of Cost of Sales (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>104</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>999095 - Disclosure - Operating Expenses - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OperatingExpensesAdditionalInformationDetail</Role>
      <ShortName>Operating Expenses - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>105</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>999096 - Disclosure - Audit and assurance services fees - Schedule of Billed and Accrued from its Independent Auditors (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AuditAndAssuranceServicesFeesScheduleOfBilledAndAccruedFromItsIndependentAuditorsDetail</Role>
      <ShortName>Audit and assurance services fees - Schedule of Billed and Accrued from its Independent Auditors (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>106</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>999097 - Disclosure - Finance income and costs - Schedule of Components of Finance Income and Costs (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinanceIncomeAndCostsScheduleOfComponentsOfFinanceIncomeAndCostsDetail</Role>
      <ShortName>Finance income and costs - Schedule of Components of Finance Income and Costs (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>107</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>999098 - Disclosure - Finance income and costs - Schedule of Components of Finance Income and Costs (Paranthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinanceIncomeAndCostsScheduleOfComponentsOfFinanceIncomeAndCostsParantheticalDetail</Role>
      <ShortName>Finance income and costs - Schedule of Components of Finance Income and Costs (Paranthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>999099 - Disclosure - Other non-operating income / expenses - Schedule of Components of Other Non-Operating Income / Expenses (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherNonOperatingIncomeExpensesScheduleOfComponentsOfOtherNonOperatingIncomeExpensesDetail</Role>
      <ShortName>Other non-operating income / expenses - Schedule of Components of Other Non-Operating Income / Expenses (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>999100 - Disclosure - Income taxes - Disclosure of Current and Deferred Income Tax Charge (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IncomeTaxesDisclosureOfCurrentAndDeferredIncomeTaxChargeDetail</Role>
      <ShortName>Income taxes - Disclosure of Current and Deferred Income Tax Charge (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>999101 - Disclosure - Income taxes - Disclosure of reconciliation between the income tax benefit expense (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IncomeTaxesDisclosureOfReconciliationBetweenTheIncomeTaxBenefitExpenseDetail</Role>
      <ShortName>Income taxes - Disclosure of reconciliation between the income tax benefit expense (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>999102 - Disclosure - Income taxes - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IncomeTaxesAdditionalInformationDetail</Role>
      <ShortName>Income taxes - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>999103 - Disclosure - Deferred tax balances - Schedule of deferred tax positions included in consolidated financial statements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DeferredTaxBalancesScheduleOfDeferredTaxPositionsIncludedInConsolidatedFinancialStatementsDetail</Role>
      <ShortName>Deferred tax balances - Schedule of deferred tax positions included in consolidated financial statements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>113</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>999104 - Disclosure - Deferred tax balances - Schedule of deferred income tax assets and liabilities during the year (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DeferredTaxBalancesScheduleOfDeferredIncomeTaxAssetsAndLiabilitiesDuringTheYearDetail</Role>
      <ShortName>Deferred tax balances - Schedule of deferred income tax assets and liabilities during the year (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>114</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>999105 - Disclosure - Deferred tax balances - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DeferredTaxBalancesAdditionalInformationDetail</Role>
      <ShortName>Deferred tax balances - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>115</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>999106 - Disclosure - Components of other comprehensive income - Summary of Components of other comprehensive income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ComponentsOfOtherComprehensiveIncomeSummaryOfComponentsOfOtherComprehensiveIncomeDetail</Role>
      <ShortName>Components of other comprehensive income - Summary of Components of other comprehensive income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>116</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>999107 - Disclosure - Components of other comprehensive income - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ComponentsOfOtherComprehensiveIncomeAdditionalInformationDetail</Role>
      <ShortName>Components of other comprehensive income - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>117</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>999108 - Disclosure - Earnings per share - Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Basic Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfProfitLossAttributableToTheOwnersOfTheParentForCalculatingBasicEarningsPerShareDetail</Role>
      <ShortName>Earnings per share - Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Basic Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>118</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>999109 - Disclosure - Earnings per share - Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Basic Earnings Per Share (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfProfitLossAttributableToTheOwnersOfTheParentForCalculatingBasicEarningsPerShareParentheticalDetail</Role>
      <ShortName>Earnings per share - Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Basic Earnings Per Share (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>119</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R120.htm</HtmlFileName>
      <LongName>999110 - Disclosure - Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Basic Earnings Per Share Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfWeightedAverageNumberOfSharesUsedInCalculatingBasicEarningsPerShareValueDetail</Role>
      <ShortName>Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Basic Earnings Per Share Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>120</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R121.htm</HtmlFileName>
      <LongName>999111 - Disclosure - Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Basic Earnings Per Share Value (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfWeightedAverageNumberOfSharesUsedInCalculatingBasicEarningsPerShareValueParentheticalDetail</Role>
      <ShortName>Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Basic Earnings Per Share Value (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>121</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>999112 - Disclosure - Earnings per share -  Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Diluted Earnings Per Share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfProfitLossAttributableToTheOwnersOfTheParentForCalculatingDilutedEarningsPerShareDetail</Role>
      <ShortName>Earnings per share -  Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Diluted Earnings Per Share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>122</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>999113 - Disclosure - Earnings per share -  Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Diluted Earnings Per Share (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfProfitLossAttributableToTheOwnersOfTheParentForCalculatingDilutedEarningsPerShareParentheticalDetail</Role>
      <ShortName>Earnings per share -  Schedule of Profit Loss Attributable to the Owners of the Parent for Calculating Diluted Earnings Per Share (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>123</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>999114 - Disclosure - Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Diluted Earnings Per Share Value (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfWeightedAverageNumberOfSharesUsedInCalculatingDilutedEarningsPerShareValueDetail</Role>
      <ShortName>Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Diluted Earnings Per Share Value (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>124</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R125.htm</HtmlFileName>
      <LongName>999115 - Disclosure - Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Diluted Earnings Per Share Value (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareScheduleOfWeightedAverageNumberOfSharesUsedInCalculatingDilutedEarningsPerShareValueParentheticalDetail</Role>
      <ShortName>Earnings per share -  Schedule of Weighted Average Number of Shares used in Calculating Diluted Earnings Per Share Value (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>125</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R126.htm</HtmlFileName>
      <LongName>999116 - Disclosure - Earnings per share - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EarningsPerShareAdditionalInformationDetail</Role>
      <ShortName>Earnings per share - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>126</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R127.htm</HtmlFileName>
      <LongName>999117 - Disclosure - Dividends paid and proposed - Schedule of Gross Dividends Declared and Paid (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedScheduleOfGrossDividendsDeclaredAndPaidDetail</Role>
      <ShortName>Dividends paid and proposed - Schedule of Gross Dividends Declared and Paid (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>127</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R128.htm</HtmlFileName>
      <LongName>999118 - Disclosure - Dividends paid and proposed - Schedule of Gross Dividends Declared and Paid (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedScheduleOfGrossDividendsDeclaredAndPaidParentheticalDetail</Role>
      <ShortName>Dividends paid and proposed - Schedule of Gross Dividends Declared and Paid (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>128</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>999119 - Disclosure - Dividends paid and proposed - Schedule of Dividends Proposed (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedScheduleOfDividendsProposedDetail</Role>
      <ShortName>Dividends paid and proposed - Schedule of Dividends Proposed (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>129</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>999120 - Disclosure - Dividends paid and proposed - Schedule of Dividends Proposed  (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedScheduleOfDividendsProposedParentheticalDetail</Role>
      <ShortName>Dividends paid and proposed - Schedule of Dividends Proposed  (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>130</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>999121 - Disclosure - Dividends paid and proposed - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/DividendsPaidAndProposedAdditionalInformationDetail</Role>
      <ShortName>Dividends paid and proposed - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>131</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R132.htm</HtmlFileName>
      <LongName>999122 - Disclosure - Property, plant and equipment - Schedule of Property, Plant and Equipment (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipmentScheduleOfPropertyPlantAndEquipmentDetail</Role>
      <ShortName>Property, plant and equipment - Schedule of Property, Plant and Equipment (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>132</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R133.htm</HtmlFileName>
      <LongName>999123 - Disclosure - Property, plant and equipment - Schedule of Property, Plant and Equipment (Detail) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipmentScheduleOfPropertyPlantAndEquipmentDetailParenthetical</Role>
      <ShortName>Property, plant and equipment - Schedule of Property, Plant and Equipment (Detail) (Parenthetical)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>133</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R134.htm</HtmlFileName>
      <LongName>999124 - Disclosure - Property, plant and equipment - Schedule of Post-Tax Discount Rates Used in Impairment Test (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipmentScheduleOfPostTaxDiscountRatesUsedInImpairmentTestDetail</Role>
      <ShortName>Property, plant and equipment - Schedule of Post-Tax Discount Rates Used in Impairment Test (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>134</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>999125 - Disclosure - Property, plant and equipment - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/PropertyPlantAndEquipmentAdditionalInformationDetail</Role>
      <ShortName>Property, plant and equipment - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>135</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>999126 - Disclosure - Assets in the course of construction - Schedule of Assets in the Course of Construction (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsInTheCourseOfConstructionScheduleOfAssetsInTheCourseOfConstructionDetail</Role>
      <ShortName>Assets in the course of construction - Schedule of Assets in the Course of Construction (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>136</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R137.htm</HtmlFileName>
      <LongName>999127 - Disclosure - Assets in the course of construction - Schedule of Assets in the Course of Construction (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsInTheCourseOfConstructionScheduleOfAssetsInTheCourseOfConstructionParentheticalDetail</Role>
      <ShortName>Assets in the course of construction - Schedule of Assets in the Course of Construction (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>137</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>999128 - Disclosure - Assets in the course of construction - Addditional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsInTheCourseOfConstructionAddditionalInformationDetail</Role>
      <ShortName>Assets in the course of construction - Addditional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>138</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R139.htm</HtmlFileName>
      <LongName>999129 - Disclosure - Intangible Assets - Schedule Of Reconciliation Of Changes In Intangible Assets And Goodwill (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IntangibleAssetsScheduleOfReconciliationOfChangesInIntangibleAssetsAndGoodwillDetail</Role>
      <ShortName>Intangible Assets - Schedule Of Reconciliation Of Changes In Intangible Assets And Goodwill (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>139</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R140.htm</HtmlFileName>
      <LongName>999130 - Disclosure - Intangible assets - Schedule Of Definite Life Intangible Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IntangibleAssetsScheduleOfDefiniteLifeIntangibleAssetsDetail</Role>
      <ShortName>Intangible assets - Schedule Of Definite Life Intangible Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>140</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R141.htm</HtmlFileName>
      <LongName>999131 - Disclosure - Intangible assets - Additional information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/IntangibleAssetsAdditionalInformationDetail</Role>
      <ShortName>Intangible assets - Additional information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>141</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R142.htm</HtmlFileName>
      <LongName>999132 - Disclosure - Other financial assets - Schedule of Changes in the Fair Value of Financial Assets at FVTPL (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherFinancialAssetsScheduleOfChangesInTheFairValueOfFinancialAssetsAtFvtplDetail</Role>
      <ShortName>Other financial assets - Schedule of Changes in the Fair Value of Financial Assets at FVTPL (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>142</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R143.htm</HtmlFileName>
      <LongName>999133 - Disclosure - Other financial assets - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherFinancialAssetsAdditionalInformationDetail</Role>
      <ShortName>Other financial assets - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>143</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R144.htm</HtmlFileName>
      <LongName>999134 - Disclosure - Investments accounted for using equity method - Schedule of Joint Ventures (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethodScheduleOfJointVenturesDetail</Role>
      <ShortName>Investments accounted for using equity method - Schedule of Joint Ventures (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>144</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R145.htm</HtmlFileName>
      <LongName>999135 - Disclosure - Investments accounted for using equity method - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethodAdditionalInformationDetail</Role>
      <ShortName>Investments accounted for using equity method - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>145</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R146.htm</HtmlFileName>
      <LongName>999136 - Disclosure - Investments accounted for using equity method - Schedule of Financial Information of Joint Ventures (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InvestmentsAccountedForUsingEquityMethodScheduleOfFinancialInformationOfJointVenturesDetail</Role>
      <ShortName>Investments accounted for using equity method - Schedule of Financial Information of Joint Ventures (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>146</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R147.htm</HtmlFileName>
      <LongName>999137 - Disclosure - Inventories - Schedule of Current Inventories (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InventoriesScheduleOfCurrentInventoriesDetail</Role>
      <ShortName>Inventories - Schedule of Current Inventories (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>147</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R148.htm</HtmlFileName>
      <LongName>999138 - Disclosure - Inventories - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/InventoriesAdditionalInformationDetail</Role>
      <ShortName>Inventories - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>148</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R149.htm</HtmlFileName>
      <LongName>999139 - Disclosure - Assets and liabilities related to contracts with customers - Schedule of Assets and Liabilities Related to Contracts with Customers  (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsAndLiabilitiesRelatedToContractsWithCustomersScheduleOfAssetsAndLiabilitiesRelatedToContractsWithCustomersDetail</Role>
      <ShortName>Assets and liabilities related to contracts with customers - Schedule of Assets and Liabilities Related to Contracts with Customers  (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>149</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R150.htm</HtmlFileName>
      <LongName>999140 - Disclosure - Assets and liabilities related to contracts with customers - Schedule of Movement in Deferred Income Recognised by the Group (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/AssetsAndLiabilitiesRelatedToContractsWithCustomersScheduleOfMovementInDeferredIncomeRecognisedByTheGroupDetail</Role>
      <ShortName>Assets and liabilities related to contracts with customers - Schedule of Movement in Deferred Income Recognised by the Group (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>150</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R151.htm</HtmlFileName>
      <LongName>999141 - Disclosure - Trade And Other Receivables - Schedule Of Trade And Other Receivables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherReceivablesScheduleOfTradeAndOtherReceivablesDetail</Role>
      <ShortName>Trade And Other Receivables - Schedule Of Trade And Other Receivables (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>151</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R152.htm</HtmlFileName>
      <LongName>999142 - Disclosure - Trade And Other Receivables - Schedule Of Provision Of Impairment On Trade And Other Receivables (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherReceivablesScheduleOfProvisionOfImpairmentOnTradeAndOtherReceivablesDetail</Role>
      <ShortName>Trade And Other Receivables - Schedule Of Provision Of Impairment On Trade And Other Receivables (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>152</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R153.htm</HtmlFileName>
      <LongName>999143 - Disclosure - Trade And Other Receivables - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherReceivablesAdditionalInformationDetail</Role>
      <ShortName>Trade And Other Receivables - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>153</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R154.htm</HtmlFileName>
      <LongName>999144 - Disclosure - Financial Instruments - Summary of Comparison by category of carrying amounts and fair values of all the Group's financial instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsSummaryOfComparisonByCategoryOfCarryingAmountsAndFairValuesOfAllTheGroupSFinancialInstrumentsDetail</Role>
      <ShortName>Financial Instruments - Summary of Comparison by category of carrying amounts and fair values of all the Group's financial instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>154</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R155.htm</HtmlFileName>
      <LongName>999145 - Disclosure - Financial instruments - Summary of Fair value measurements using significant unobservable inputs (level 3) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsSummaryOfFairValueMeasurementsUsingSignificantUnobservableInputsLevel3Detail</Role>
      <ShortName>Financial instruments - Summary of Fair value measurements using significant unobservable inputs (level 3) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>155</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R156.htm</HtmlFileName>
      <LongName>999146 - Disclosure - Financial instruments - Disclosure Of Changes In Level 3 Financial Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsDisclosureOfChangesInLevel3FinancialLiabilitiesDetail</Role>
      <ShortName>Financial instruments - Disclosure Of Changes In Level 3 Financial Liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>156</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R157.htm</HtmlFileName>
      <LongName>999147 - Disclosure - Financial Instruments - Summary Of Significant Unobservable Inputs Used In Level 3 Fair Value Measurements (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsSummaryOfSignificantUnobservableInputsUsedInLevel3FairValueMeasurementsDetail</Role>
      <ShortName>Financial Instruments - Summary Of Significant Unobservable Inputs Used In Level 3 Fair Value Measurements (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>157</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R158.htm</HtmlFileName>
      <LongName>999148 - Disclosure - Financial Instruments - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialInstrumentsAdditionalInformationDetail</Role>
      <ShortName>Financial Instruments - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>158</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R159.htm</HtmlFileName>
      <LongName>999149 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Undiscounted Cash Flows of the Non-Derivative Financial Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfUndiscountedCashFlowsOfTheNonDerivativeFinancialLiabilitiesDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Undiscounted Cash Flows of the Non-Derivative Financial Liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>159</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R160.htm</HtmlFileName>
      <LongName>999150 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Aggregate Net Foreign Exchange Gains/ Losses Recognized in Profit or Loss (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfAggregateNetForeignExchangeGainsLossesRecognizedInProfitOrLossDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Aggregate Net Foreign Exchange Gains/ Losses Recognized in Profit or Loss (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>160</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R161.htm</HtmlFileName>
      <LongName>999151 - Disclosure - Financial Risk Management Objectives and Policies  - Schedule of Excluded Components are Accounted Separately in the Consolidated Statement of Comprehensive Income (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfExcludedComponentsAreAccountedSeparatelyInTheConsolidatedStatementOfComprehensiveIncomeDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies  - Schedule of Excluded Components are Accounted Separately in the Consolidated Statement of Comprehensive Income (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>161</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R162.htm</HtmlFileName>
      <LongName>999152 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Hedged Portion of USD Statement of Financial Position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfHedgedPortionOfUsdStatementOfFinancialPositionDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Hedged Portion of USD Statement of Financial Position (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>162</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R163.htm</HtmlFileName>
      <LongName>999153 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Other Comprehensive Income with No Impact on Profit and Loss (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfOtherComprehensiveIncomeWithNoImpactOnProfitAndLossDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Other Comprehensive Income with No Impact on Profit and Loss (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>163</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R164.htm</HtmlFileName>
      <LongName>999154 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Carrying Amount of The Group's Debt Between Fixed and Floating Rate (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfCarryingAmountOfTheGroupSDebtBetweenFixedAndFloatingRateDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Carrying Amount of The Group's Debt Between Fixed and Floating Rate (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>164</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R165.htm</HtmlFileName>
      <LongName>999155 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Loss Expectancy Rates Based on the History of Losses to Create a Provision Matrix (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfLossExpectancyRatesBasedOnTheHistoryOfLossesToCreateAProvisionMatrixDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Loss Expectancy Rates Based on the History of Losses to Create a Provision Matrix (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>165</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R166.htm</HtmlFileName>
      <LongName>999156 - Disclosure - Financial Risk Management Objectives and Policies - Schedule of Movement in Provisions for Trade Receivables and Unbilled Accrued Revenue (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesScheduleOfMovementInProvisionsForTradeReceivablesAndUnbilledAccruedRevenueDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Schedule of Movement in Provisions for Trade Receivables and Unbilled Accrued Revenue (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>166</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R167.htm</HtmlFileName>
      <LongName>999157 - Disclosure - Financial Risk Management Objectives and Policies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FinancialRiskManagementObjectivesAndPoliciesAdditionalInformationDetail</Role>
      <ShortName>Financial Risk Management Objectives and Policies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>167</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R168.htm</HtmlFileName>
      <LongName>999158 - Disclosure - Cash and cash equivalents - Summary of Restricted Cash and Cash Equivalents (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashAndCashEquivalentsSummaryOfRestrictedCashAndCashEquivalentsDetail</Role>
      <ShortName>Cash and cash equivalents - Summary of Restricted Cash and Cash Equivalents (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>168</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R169.htm</HtmlFileName>
      <LongName>999159 - Disclosure - Cash and Cash Equivalents - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashAndCashEquivalentsAdditionalInformationDetail</Role>
      <ShortName>Cash and Cash Equivalents - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>169</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R170.htm</HtmlFileName>
      <LongName>999160 - Disclosure - Shareholders' equity - Schedule of movement between the opening and closing number of shares issued per class of share (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareholdersEquityScheduleOfMovementBetweenTheOpeningAndClosingNumberOfSharesIssuedPerClassOfShareDetail</Role>
      <ShortName>Shareholders' equity - Schedule of movement between the opening and closing number of shares issued per class of share (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>170</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R171.htm</HtmlFileName>
      <LongName>999161 - Disclosure - Shareholders' equity - Schedule of disclosure of treasury shares in consolidated statement of financial position (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareholdersEquityScheduleOfDisclosureOfTreasurySharesInConsolidatedStatementOfFinancialPositionDetail</Role>
      <ShortName>Shareholders' equity - Schedule of disclosure of treasury shares in consolidated statement of financial position (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>171</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R172.htm</HtmlFileName>
      <LongName>999162 - Disclosure - Shareholders' equity - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareholdersEquityAdditionalInformationDetail</Role>
      <ShortName>Shareholders' equity - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>172</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R173.htm</HtmlFileName>
      <LongName>999163 - Disclosure - Non-controlling interests - Schedule of Financial Information of Non Controlling interests (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/NonControllingInterestsScheduleOfFinancialInformationOfNonControllingInterestsDetail</Role>
      <ShortName>Non-controlling interests - Schedule of Financial Information of Non Controlling interests (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>173</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R174.htm</HtmlFileName>
      <LongName>999164 - Disclosure - Share-Based Compensation Plans - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansAdditionalInformationDetail</Role>
      <ShortName>Share-Based Compensation Plans - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>174</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R175.htm</HtmlFileName>
      <LongName>999165 - Disclosure - Share-Based Compensation Plans - Summary of Number and Weighted Average Exercise Prices of Share Options (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansSummaryOfNumberAndWeightedAverageExercisePricesOfShareOptionsDetail</Role>
      <ShortName>Share-Based Compensation Plans - Summary of Number and Weighted Average Exercise Prices of Share Options (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>175</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R176.htm</HtmlFileName>
      <LongName>999166 - Disclosure - Share-Based Compensation Plans - Summary of Movements in the Number of Share Options Outstanding and Weighted Average Exercise Price (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansSummaryOfMovementsInTheNumberOfShareOptionsOutstandingAndWeightedAverageExercisePriceDetail</Role>
      <ShortName>Share-Based Compensation Plans - Summary of Movements in the Number of Share Options Outstanding and Weighted Average Exercise Price (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>176</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R177.htm</HtmlFileName>
      <LongName>999167 - Disclosure - Share-Based Compensation Plans - Summary of Expiry Date and Exercise Prices of Share Options Outstanding (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansSummaryOfExpiryDateAndExercisePricesOfShareOptionsOutstandingDetail</Role>
      <ShortName>Share-Based Compensation Plans - Summary of Expiry Date and Exercise Prices of Share Options Outstanding (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>177</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R178.htm</HtmlFileName>
      <LongName>999168 - Disclosure - Share-Based Compensation Plans - Summary of Number and Weighted Average Exercise Prices of Other Equity Instruments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansSummaryOfNumberAndWeightedAverageExercisePricesOfOtherEquityInstrumentsDetail</Role>
      <ShortName>Share-Based Compensation Plans - Summary of Number and Weighted Average Exercise Prices of Other Equity Instruments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>178</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R179.htm</HtmlFileName>
      <LongName>999169 - Disclosure - Share-Based Compensation Plans - Summary of Average Value of Inputs to the Model (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ShareBasedCompensationPlansSummaryOfAverageValueOfInputsToTheModelDetail</Role>
      <ShortName>Share-Based Compensation Plans - Summary of Average Value of Inputs to the Model (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>179</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R180.htm</HtmlFileName>
      <LongName>999170 - Disclosure - Borrowings - Schedule of Interest Bearing Borrowings (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BorrowingsScheduleOfInterestBearingBorrowingsDetail</Role>
      <ShortName>Borrowings - Schedule of Interest Bearing Borrowings (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>180</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R181.htm</HtmlFileName>
      <LongName>999171 - Disclosure - Borrowings - Schedule of Interest Bearing Borrowings (Parentheticals) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BorrowingsScheduleOfInterestBearingBorrowingsParentheticalsDetail</Role>
      <ShortName>Borrowings - Schedule of Interest Bearing Borrowings (Parentheticals) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>181</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R182.htm</HtmlFileName>
      <LongName>999172 - Disclosure - Borrowings - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/BorrowingsAdditionalInformationDetail</Role>
      <ShortName>Borrowings - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>182</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R183.htm</HtmlFileName>
      <LongName>999173 - Disclosure - Provisions - Schedule of Detailed Information of Provisions Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ProvisionsScheduleOfDetailedInformationOfProvisionsExplanatoryDetail</Role>
      <ShortName>Provisions - Schedule of Detailed Information of Provisions Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>183</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R184.htm</HtmlFileName>
      <LongName>999174 - Disclosure - Provisions - Disclosure of Movements of Provisions Explanatory  (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ProvisionsDisclosureOfMovementsOfProvisionsExplanatoryDetail</Role>
      <ShortName>Provisions - Disclosure of Movements of Provisions Explanatory  (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>184</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R185.htm</HtmlFileName>
      <LongName>999175 - Disclosure - Provisions - Additional information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ProvisionsAdditionalInformationDetail</Role>
      <ShortName>Provisions - Additional information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>185</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R186.htm</HtmlFileName>
      <LongName>999176 - Disclosure - Trade and other payables - Disclosure Of Trade And Other Payables Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherPayablesDisclosureOfTradeAndOtherPayablesExplanatoryDetail</Role>
      <ShortName>Trade and other payables - Disclosure Of Trade And Other Payables Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>186</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R187.htm</HtmlFileName>
      <LongName>999177 - Disclosure - Trade and other payables -  Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/TradeAndOtherPayablesAdditionalInformationDetail</Role>
      <ShortName>Trade and other payables -  Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>187</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R188.htm</HtmlFileName>
      <LongName>999178 - Disclosure - Other long-term liabilities - Schedule of Disclosure Of Other Long Term Liabilities Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherLongTermLiabilitiesScheduleOfDisclosureOfOtherLongTermLiabilitiesExplanatoryDetail</Role>
      <ShortName>Other long-term liabilities - Schedule of Disclosure Of Other Long Term Liabilities Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>188</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R189.htm</HtmlFileName>
      <LongName>999179 - Disclosure - Other long-term liabilities - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/OtherLongTermLiabilitiesAdditionalInformationDetail</Role>
      <ShortName>Other long-term liabilities - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>189</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R190.htm</HtmlFileName>
      <LongName>999180 - Disclosure - Employee benefit obligations - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsAdditionalInformationDetail</Role>
      <ShortName>Employee benefit obligations - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>190</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R191.htm</HtmlFileName>
      <LongName>999181 - Disclosure - Employee benefit obligations - Schedule of defined benefit plans (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfDefinedBenefitPlansDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of defined benefit plans (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>191</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R192.htm</HtmlFileName>
      <LongName>999182 - Disclosure - Employee benefit obligations - Schedule of amounts recognized in the consolidated income statement (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfAmountsRecognizedInTheConsolidatedIncomeStatementDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of amounts recognized in the consolidated income statement (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>192</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R193.htm</HtmlFileName>
      <LongName>999183 - Disclosure - Employee benefit obligations - Schedule of changes in the defined benefit obligation and fair value of plan assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfChangesInTheDefinedBenefitObligationAndFairValueOfPlanAssetsDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of changes in the defined benefit obligation and fair value of plan assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>193</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R194.htm</HtmlFileName>
      <LongName>999184 - Disclosure - Employee benefit obligations - Schedule of major categories of the defined benefit plan assets for the SRP (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfMajorCategoriesOfTheDefinedBenefitPlanAssetsForTheSrpDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of major categories of the defined benefit plan assets for the SRP (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>194</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R195.htm</HtmlFileName>
      <LongName>999185 - Disclosure - Employee benefit obligations - Schedule of major categories of the defined benefit plan assets for the SRP (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfMajorCategoriesOfTheDefinedBenefitPlanAssetsForTheSrpParentheticalDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of major categories of the defined benefit plan assets for the SRP (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>195</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R196.htm</HtmlFileName>
      <LongName>999186 - Disclosure - Employee benefit obligations - Schedule of amounts recognized for Intelsat's postretirement benefit plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfAmountsRecognizedForIntelsatSPostretirementBenefitPlanDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of amounts recognized for Intelsat's postretirement benefit plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>196</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R197.htm</HtmlFileName>
      <LongName>999187 - Disclosure - Employee benefit obligations - Schedule of change in the defined benefit obligation (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfChangeInTheDefinedBenefitObligationDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of change in the defined benefit obligation (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>197</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R198.htm</HtmlFileName>
      <LongName>999188 - Disclosure - Employee benefit obligations  - Schedule of amounts recognized for the legacy SES postretirement benefit plan (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfAmountsRecognizedForTheLegacySesPostretirementBenefitPlanDetail</Role>
      <ShortName>Employee benefit obligations  - Schedule of amounts recognized for the legacy SES postretirement benefit plan (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>198</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R199.htm</HtmlFileName>
      <LongName>999189 - Disclosure - Employee benefit obligations - Schedule of significant actuarial assumptions and sensitivity analysis (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfSignificantActuarialAssumptionsAndSensitivityAnalysisDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of significant actuarial assumptions and sensitivity analysis (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>199</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R200.htm</HtmlFileName>
      <LongName>999190 - Disclosure - Employee benefit obligations - Schedule of information about maturity profile of defined benefit obligation (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/EmployeeBenefitObligationsScheduleOfInformationAboutMaturityProfileOfDefinedBenefitObligationDetail</Role>
      <ShortName>Employee benefit obligations - Schedule of information about maturity profile of defined benefit obligation (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>200</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R201.htm</HtmlFileName>
      <LongName>999191 - Disclosure - Fixed Assets Suppliers - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FixedAssetsSuppliersAdditionalInformationDetail</Role>
      <ShortName>Fixed Assets Suppliers - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>201</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R202.htm</HtmlFileName>
      <LongName>999192 - Disclosure - Fixed Assets Suppliers - Schedule of Fixed Assets Suppliers (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/FixedAssetsSuppliersScheduleOfFixedAssetsSuppliersDetail</Role>
      <ShortName>Fixed Assets Suppliers - Schedule of Fixed Assets Suppliers (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>202</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R203.htm</HtmlFileName>
      <LongName>999193 - Disclosure - Commitments and contingencies - Schedule of Arising Capital Expenditure Commitments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CommitmentsAndContingenciesScheduleOfArisingCapitalExpenditureCommitmentsDetail</Role>
      <ShortName>Commitments and contingencies - Schedule of Arising Capital Expenditure Commitments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>203</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R204.htm</HtmlFileName>
      <LongName>999194 - Disclosure - Commitments and contingencies - Schedule of Performance Incentive Obligations and Future Interest Payments (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CommitmentsAndContingenciesScheduleOfPerformanceIncentiveObligationsAndFutureInterestPaymentsDetail</Role>
      <ShortName>Commitments and contingencies - Schedule of Performance Incentive Obligations and Future Interest Payments (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>204</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R205.htm</HtmlFileName>
      <LongName>999195 - Disclosure - Commitments and contingencies - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CommitmentsAndContingenciesAdditionalInformationDetail</Role>
      <ShortName>Commitments and contingencies - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>205</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R206.htm</HtmlFileName>
      <LongName>999196 - Disclosure - Leases - Schedule Of Maturity Analysis Of Finance Lease Payments Receivable (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesScheduleOfMaturityAnalysisOfFinanceLeasePaymentsReceivableDetail</Role>
      <ShortName>Leases - Schedule Of Maturity Analysis Of Finance Lease Payments Receivable (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>206</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R207.htm</HtmlFileName>
      <LongName>999197 - Disclosure - Leases - Schedule Of Amounts Recognised In The Consolidated Income Statement Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesScheduleOfAmountsRecognisedInTheConsolidatedIncomeStatementExplanatoryDetail</Role>
      <ShortName>Leases - Schedule Of Amounts Recognised In The Consolidated Income Statement Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>207</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R208.htm</HtmlFileName>
      <LongName>999198 - Disclosure - Leases - Schedule Of Quantitative Information About Right-Of-Use Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesScheduleOfQuantitativeInformationAboutRightOfUseAssetsDetail</Role>
      <ShortName>Leases - Schedule Of Quantitative Information About Right-Of-Use Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>208</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R209.htm</HtmlFileName>
      <LongName>999199 - Disclosure - Leases - Schedule Of Maturity Analysis For Non-Derivative Financial Liabilities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesScheduleOfMaturityAnalysisForNonDerivativeFinancialLiabilitiesDetail</Role>
      <ShortName>Leases - Schedule Of Maturity Analysis For Non-Derivative Financial Liabilities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>209</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R210.htm</HtmlFileName>
      <LongName>999200 - Disclosure - Leases - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesAdditionalInformationDetail</Role>
      <ShortName>Leases - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>210</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R211.htm</HtmlFileName>
      <LongName>999201 - Disclosure - Leases - Schedule Of Depreciation Charge And Finance Cost Of Right Of Use Assets Explanatory (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/LeasesScheduleOfDepreciationChargeAndFinanceCostOfRightOfUseAssetsExplanatoryDetail</Role>
      <ShortName>Leases - Schedule Of Depreciation Charge And Finance Cost Of Right Of Use Assets Explanatory (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>211</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R212.htm</HtmlFileName>
      <LongName>999202 - Disclosure - Cash flow information - Summary Of An Analysis Of Net Debt And The Movements In Net Debt (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashFlowInformationSummaryOfAnAnalysisOfNetDebtAndTheMovementsInNetDebtDetail</Role>
      <ShortName>Cash flow information - Summary Of An Analysis Of Net Debt And The Movements In Net Debt (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>212</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R213.htm</HtmlFileName>
      <LongName>999203 - Disclosure - Cash flow information - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashFlowInformationAdditionalInformationDetail</Role>
      <ShortName>Cash flow information - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>213</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R214.htm</HtmlFileName>
      <LongName>999204 - Disclosure - Cash flow information - Schedule Of Net Debt Reconciliation (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CashFlowInformationScheduleOfNetDebtReconciliationDetail</Role>
      <ShortName>Cash flow information - Schedule Of Net Debt Reconciliation (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>214</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R215.htm</HtmlFileName>
      <LongName>999205 - Disclosure - Related parties - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RelatedPartiesAdditionalInformationDetail</Role>
      <ShortName>Related parties - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>215</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R216.htm</HtmlFileName>
      <LongName>999206 - Disclosure - Related parties - Summary of Key Management (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RelatedPartiesSummaryOfKeyManagementDetail</Role>
      <ShortName>Related parties - Summary of Key Management (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>216</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R217.htm</HtmlFileName>
      <LongName>999207 - Disclosure - Related parties - Summary of Key Management (Parenthetical) (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/RelatedPartiesSummaryOfKeyManagementParentheticalDetail</Role>
      <ShortName>Related parties - Summary of Key Management (Parenthetical) (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>217</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R218.htm</HtmlFileName>
      <LongName>999208 - Disclosure - C-band repurposing - Summary of Costs and Expected Reimbursements of Assets (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CBandRepurposingSummaryOfCostsAndExpectedReimbursementsOfAssetsDetail</Role>
      <ShortName>C-band repurposing - Summary of Costs and Expected Reimbursements of Assets (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>218</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R219.htm</HtmlFileName>
      <LongName>999209 - Disclosure - C-band repurposing - Additional Information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/CBandRepurposingAdditionalInformationDetail</Role>
      <ShortName>C-band repurposing - Additional Information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>219</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R220.htm</HtmlFileName>
      <LongName>999210 - Disclosure - Subsequent events - Additional information (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/SubsequentEventsAdditionalInformationDetail</Role>
      <ShortName>Subsequent events - Additional information (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>220</Position>
    </Report>
    <Report instance="d33769d20f.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R221.htm</HtmlFileName>
      <LongName>999211 - Disclosure - Consolidated subsidiaries, associates - Schedule of Consolidated Structured Entities (Detail)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.ses.com/role/ConsolidatedSubsidiariesAssociatesScheduleOfConsolidatedStructuredEntitiesDetail</Role>
      <ShortName>Consolidated subsidiaries, associates - Schedule of Consolidated Structured Entities (Detail)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>221</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="20-F" isDefinitelyFs="true" isIfrs="true" isUsgaap="true" original="d33769d20f.htm">d33769d20f.htm</File>
    <File>sgbaf-20251231.xsd</File>
  </InputFiles>
  <SupplementalFiles>
    <File>g33769g00a89.jpg</File>
    <File>g33769g46x47.jpg</File>
    <File>g33769g85h22.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="11">http://xbrl.sec.gov/cyd/2025</BaseTaxonomy>
    <BaseTaxonomy items="40">http://xbrl.sec.gov/dei/2025</BaseTaxonomy>
    <BaseTaxonomy items="1">http://xbrl.sec.gov/ecd/2025</BaseTaxonomy>
    <BaseTaxonomy items="2589">https://xbrl.ifrs.org/taxonomy/2025-03-27/ifrs-full</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>false</HasPresentationLinkbase>
  <HasCalculationLinkbase>false</HasCalculationLinkbase>
</FilingSummary>
