<?xml version='1.0' encoding='utf-8'?>
<FilingSummary>
  <Version>3.25.1</Version>
  <ProcessingTime/>
  <ReportFormat>html</ReportFormat>
  <ContextCount>704</ContextCount>
  <ElementCount>633</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>130</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>12</UnitCount>
  <MyReports>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>1100090 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DocumentDocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>1</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>1100100 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedBalanceSheets</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>2</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>1100105 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>3</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>1100200 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfOperations</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>4</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>1100300 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK SUBJECT TO POSSIBLE REDEMPTION AND STOCKHOLDERS' DEFICIT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfChangesInCommonStockSubjectToPossibleRedemptionAndStockholdersDeficit</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK SUBJECT TO POSSIBLE REDEMPTION AND STOCKHOLDERS' DEFICIT</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>5</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>1100400 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>6</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>1110101 - Disclosure - Description of Organization and Business Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperations</Role>
      <ShortName>Description of Organization and Business Operations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>7</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>1110201 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>8</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>1110301 - Disclosure - Initial Public Offering</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInitialPublicOffering</Role>
      <ShortName>Initial Public Offering</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>9</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>1110401 - Disclosure - Private Placement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePrivatePlacement</Role>
      <ShortName>Private Placement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>10</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>1110501 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactions</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>11</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>1110601 - Disclosure - Stockholders' Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersEquity</Role>
      <ShortName>Stockholders' Equity</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>12</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>1110701 - Disclosure - Warrants</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureWarrants</Role>
      <ShortName>Warrants</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>13</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>1110801 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingencies</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>14</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>1110901 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>15</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>1111001 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxes</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>16</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>1111101 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSegmentInformation</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>17</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>1111201 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>18</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>1120202 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>19</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>1130203 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>20</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>1130903 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>21</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>1140101 - Disclosure - Description of Organization and Business Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperationsDetails</Role>
      <ShortName>Description of Organization and Business Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperations</ParentRole>
      <Position>22</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>1140201 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetails</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>23</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>1140202 - Disclosure - Summary of Significant Accounting Policies - Common stock subject to possible redemption (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCommonStockSubjectToPossibleRedemptionDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Common stock subject to possible redemption (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>24</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>1140203 - Disclosure - Summary of Significant Accounting Policies - Net income (loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesNetIncomeLossDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Net income (loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>25</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>1140204 - Disclosure - Summary of Significant Accounting Policies - Calculation of basic and diluted net income (loss) per common share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCalculationOfBasicAndDilutedNetIncomeLossPerCommonShareDetails</Role>
      <ShortName>Summary of Significant Accounting Policies - Calculation of basic and diluted net income (loss) per common share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>26</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>1140301 - Disclosure - Initial Public Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInitialPublicOfferingDetails</Role>
      <ShortName>Initial Public Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureInitialPublicOffering</ParentRole>
      <Position>27</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>1140401 - Disclosure - Private Placement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePrivatePlacementDetails</Role>
      <ShortName>Private Placement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosurePrivatePlacement</ParentRole>
      <Position>28</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>1140501 - Disclosure - Related Party Transactions - Founder Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsFounderSharesDetails</Role>
      <ShortName>Related Party Transactions - Founder Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>29</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>1140502 - Disclosure - Related Party Transactions - Sponsor Promissory Note (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsSponsorPromissoryNoteDetails</Role>
      <ShortName>Related Party Transactions - Sponsor Promissory Note (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>30</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>1140503 - Disclosure - Related Party Transactions - Related Party Loans, Due to Related Party and Administrative Support Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsRelatedPartyLoansDueToRelatedPartyAndAdministrativeSupportAgreementDetails</Role>
      <ShortName>Related Party Transactions - Related Party Loans, Due to Related Party and Administrative Support Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>31</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>1140601 - Disclosure - Stockholders' Equity - Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersEquityPreferredStockDetails</Role>
      <ShortName>Stockholders' Equity - Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>32</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>1140602 - Disclosure - Stockholders' Equity - Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersEquityCommonStockDetails</Role>
      <ShortName>Stockholders' Equity - Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>33</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>1140701 - Disclosure - Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureWarrantsDetails</Role>
      <ShortName>Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureWarrants</ParentRole>
      <Position>34</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>1140801 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesDetails</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>35</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>1140901 - Disclosure - Fair Value Measurements - Assets and liabilities at fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsAssetsAndLiabilitiesAtFairValueDetails</Role>
      <ShortName>Fair Value Measurements - Assets and liabilities at fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>36</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>1140902 - Disclosure - Fair Value Measurements - Change in fair value of Company's liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsChangeInFairValueOfCompanySLiabilitiesDetails</Role>
      <ShortName>Fair Value Measurements - Change in fair value of Company's liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>37</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>1140903 - Disclosure - Fair Value Measurements - Changes in fair value instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsChangesInFairValueInstrumentsDetails</Role>
      <ShortName>Fair Value Measurements - Changes in fair value instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>38</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>1140904 - Disclosure - Fair Value Measurements - Measurement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsMeasurementDetails</Role>
      <ShortName>Fair Value Measurements - Measurement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>39</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>1140905 - Disclosure - Fair Value Measurements - Non-recurring Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsNonRecurringFairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements - Non-recurring Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>40</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>1141001 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesDetails</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>41</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>1141101 - Disclosure - Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSegmentInformationDetails</Role>
      <ShortName>Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSegmentInformation</ParentRole>
      <Position>42</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>1141201 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventsDetails</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>43</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>12121200100 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedBalanceSheets</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>44</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>12121200105 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedBalanceSheetsParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>45</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>12121200200 - Statement - CONSOLIDATED STATEMENTS OF OPERATIONS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfOperations</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF OPERATIONS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>46</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R47.htm</HtmlFileName>
      <LongName>12121200300 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK SUBJECT TO POSSIBLE REDEMPTION AND STOCKHOLDERS' DEFICIT</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfChangesInCommonStockSubjectToPossibleRedemptionAndStockholdersDeficit</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN COMMON STOCK SUBJECT TO POSSIBLE REDEMPTION AND STOCKHOLDERS' DEFICIT</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>47</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R48.htm</HtmlFileName>
      <LongName>12121200400 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfCashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>48</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R49.htm</HtmlFileName>
      <LongName>12121210101 - Disclosure - Description of Organization and Business Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperationss</Role>
      <ShortName>Description of Organization and Business Operations</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>49</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R50.htm</HtmlFileName>
      <LongName>12121210201 - Disclosure - Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciess</Role>
      <ShortName>Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>50</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R51.htm</HtmlFileName>
      <LongName>12121210301 - Disclosure - Initial Public Offering</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInitialPublicOfferings</Role>
      <ShortName>Initial Public Offering</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>51</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R52.htm</HtmlFileName>
      <LongName>12121210401 - Disclosure - Private Placement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePrivatePlacements</Role>
      <ShortName>Private Placement</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>52</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R53.htm</HtmlFileName>
      <LongName>12121210501 - Disclosure - Related Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionss</Role>
      <ShortName>Related Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>53</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R54.htm</HtmlFileName>
      <LongName>12121210601 - Disclosure - Stockholders' Deficit</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersDeficit</Role>
      <ShortName>Stockholders' Deficit</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>54</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R55.htm</HtmlFileName>
      <LongName>12121210701 - Disclosure - Warrants</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureWarrantss</Role>
      <ShortName>Warrants</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>55</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R56.htm</HtmlFileName>
      <LongName>12121210801 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciess</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>56</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R57.htm</HtmlFileName>
      <LongName>12121210901 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementss</Role>
      <ShortName>Fair Value Measurements</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>57</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R58.htm</HtmlFileName>
      <LongName>12121211001 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxess</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>58</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R59.htm</HtmlFileName>
      <LongName>12121211101 - Disclosure - Segment Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSegmentInformations</Role>
      <ShortName>Segment Information</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>59</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R60.htm</HtmlFileName>
      <LongName>12121211201 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventss</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>60</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R61.htm</HtmlFileName>
      <LongName>12121220202 - Disclosure - Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPoliciess</Role>
      <ShortName>Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>61</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R62.htm</HtmlFileName>
      <LongName>12121230203 - Disclosure - Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTabless</Role>
      <ShortName>Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>62</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R63.htm</HtmlFileName>
      <LongName>12121230903 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsTabless</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureFairValueMeasurements</ParentRole>
      <Position>63</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R64.htm</HtmlFileName>
      <LongName>12121231003 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesTables</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>64</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R65.htm</HtmlFileName>
      <LongName>12121240101 - Disclosure - Description of Organization and Business Operations (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperationsDetailss</Role>
      <ShortName>Description of Organization and Business Operations (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndBusinessOperations</ParentRole>
      <Position>65</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R66.htm</HtmlFileName>
      <LongName>12121240201 - Disclosure - Summary of Significant Accounting Policies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesDetailss</Role>
      <ShortName>Summary of Significant Accounting Policies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>66</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R67.htm</HtmlFileName>
      <LongName>12121240202 - Disclosure - Summary of Significant Accounting Policies - Common stock subject to possible redemption (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCommonStockSubjectToPossibleRedemptionDetailss</Role>
      <ShortName>Summary of Significant Accounting Policies - Common stock subject to possible redemption (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>67</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R68.htm</HtmlFileName>
      <LongName>12121240203 - Disclosure - Summary of Significant Accounting Policies - Net income (loss) (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesNetIncomeLossDetailss</Role>
      <ShortName>Summary of Significant Accounting Policies - Net income (loss) (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>68</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R69.htm</HtmlFileName>
      <LongName>12121240204 - Disclosure - Summary of Significant Accounting Policies - Calculation of basic and diluted net income (loss) per common share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCalculationOfBasicAndDilutedNetIncomeLossPerCommonShareDetailss</Role>
      <ShortName>Summary of Significant Accounting Policies - Calculation of basic and diluted net income (loss) per common share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>69</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R70.htm</HtmlFileName>
      <LongName>12121240301 - Disclosure - Initial Public Offering (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInitialPublicOfferingDetailss</Role>
      <ShortName>Initial Public Offering (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureInitialPublicOffering</ParentRole>
      <Position>70</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R71.htm</HtmlFileName>
      <LongName>12121240401 - Disclosure - Private Placement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePrivatePlacementDetailss</Role>
      <ShortName>Private Placement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosurePrivatePlacement</ParentRole>
      <Position>71</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R72.htm</HtmlFileName>
      <LongName>12121240501 - Disclosure - Related Party Transactions - Founder Shares (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsFounderSharesDetailss</Role>
      <ShortName>Related Party Transactions - Founder Shares (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>72</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R73.htm</HtmlFileName>
      <LongName>12121240502 - Disclosure - Related Party Transactions - Sponsor Promissory Note (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsSponsorPromissoryNoteDetailss</Role>
      <ShortName>Related Party Transactions - Sponsor Promissory Note (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>73</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R74.htm</HtmlFileName>
      <LongName>12121240503 - Disclosure - Related Party Transactions - Related Party Loans, Due to Related Party and Administrative Support Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsRelatedPartyLoansDueToRelatedPartyAndAdministrativeSupportAgreementDetailss</Role>
      <ShortName>Related Party Transactions - Related Party Loans, Due to Related Party and Administrative Support Agreement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>74</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R75.htm</HtmlFileName>
      <LongName>12121240601 - Disclosure - Stockholders' Deficit - Preferred Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersDeficitPreferredStockDetails</Role>
      <ShortName>Stockholders' Deficit - Preferred Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>75</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R76.htm</HtmlFileName>
      <LongName>12121240602 - Disclosure - Stockholders' Deficit - Common Stock (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockholdersDeficitCommonStockDetails</Role>
      <ShortName>Stockholders' Deficit - Common Stock (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>76</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R77.htm</HtmlFileName>
      <LongName>12121240701 - Disclosure - Warrants (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureWarrantsDetailss</Role>
      <ShortName>Warrants (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureWarrants</ParentRole>
      <Position>77</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R78.htm</HtmlFileName>
      <LongName>12121240801 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesDetailss</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>78</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R79.htm</HtmlFileName>
      <LongName>12121240901 - Disclosure - Fair Value Measurements - Assets and liabilities at fair value (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsAssetsAndLiabilitiesAtFairValueDetailss</Role>
      <ShortName>Fair Value Measurements - Assets and liabilities at fair value (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>79</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R80.htm</HtmlFileName>
      <LongName>12121240902 - Disclosure - Fair Value Measurements - Change in fair value of Company's liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsChangeInFairValueOfCompanySLiabilitiesDetailss</Role>
      <ShortName>Fair Value Measurements - Change in fair value of Company's liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>80</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R81.htm</HtmlFileName>
      <LongName>12121240903 - Disclosure - Fair Value Measurements - Changes in fair value instruments (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsChangesInFairValueInstrumentsDetailss</Role>
      <ShortName>Fair Value Measurements - Changes in fair value instruments (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>81</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R82.htm</HtmlFileName>
      <LongName>12121240904 - Disclosure - Fair Value Measurements - Measurement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsMeasurementDetailss</Role>
      <ShortName>Fair Value Measurements - Measurement (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>82</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R83.htm</HtmlFileName>
      <LongName>12121240905 - Disclosure - Fair Value Measurements - Non-recurring Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureFairValueMeasurementsNonRecurringFairValueMeasurementsDetailss</Role>
      <ShortName>Fair Value Measurements - Non-recurring Fair Value Measurements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>83</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R84.htm</HtmlFileName>
      <LongName>12121241001 - Disclosure - Income Taxes -Net deferred tax assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesNetDeferredTaxAssetsDetails</Role>
      <ShortName>Income Taxes -Net deferred tax assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>84</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R85.htm</HtmlFileName>
      <LongName>12121241002 - Disclosure - Income Taxes - Income tax provision (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesIncomeTaxProvisionDetails</Role>
      <ShortName>Income Taxes - Income tax provision (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>85</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R86.htm</HtmlFileName>
      <LongName>12121241003 - Disclosure - Income Taxes - Effective Tax Reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesEffectiveTaxReconciliationDetails</Role>
      <ShortName>Income Taxes - Effective Tax Reconciliation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>86</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R87.htm</HtmlFileName>
      <LongName>12121241101 - Disclosure - Segment Information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSegmentInformationDetailss</Role>
      <ShortName>Segment Information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSegmentInformation</ParentRole>
      <Position>87</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R88.htm</HtmlFileName>
      <LongName>12121241201 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventsDetailss</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>88</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R89.htm</HtmlFileName>
      <LongName>2100100 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedBalanceSheetsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited)</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>89</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R90.htm</HtmlFileName>
      <LongName>2100105 - Statement - CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedBalanceSheetsUnauditedParenthetical</Role>
      <ShortName>CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical)</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>90</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R91.htm</HtmlFileName>
      <LongName>2100200 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfOperationsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>91</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R92.htm</HtmlFileName>
      <LongName>2100300 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfStockholdersEquityUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>92</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R93.htm</HtmlFileName>
      <LongName>2100400 - Statement - CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementCondensedConsolidatedStatementsOfCashFlowsUnaudited</Role>
      <ShortName>CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>93</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R94.htm</HtmlFileName>
      <LongName>2110101 - Disclosure - Description of Organization and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPolicies</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>94</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R95.htm</HtmlFileName>
      <LongName>2110201 - Disclosure - Digital Assets and Digital Assets Receivable</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDigitalAssetsAndDigitalAssetsReceivable</Role>
      <ShortName>Digital Assets and Digital Assets Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>95</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R96.htm</HtmlFileName>
      <LongName>2110301 - Disclosure - Notes Payable</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesPayable</Role>
      <ShortName>Notes Payable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>96</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R97.htm</HtmlFileName>
      <LongName>2110401 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesss</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>97</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R98.htm</HtmlFileName>
      <LongName>2110501 - Disclosure - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStock</Role>
      <ShortName>Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>98</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R99.htm</HtmlFileName>
      <LongName>2110601 - Disclosure - Related-Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsss</Role>
      <ShortName>Related-Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>99</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R100.htm</HtmlFileName>
      <LongName>2110701 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventsss</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>100</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R101.htm</HtmlFileName>
      <LongName>2120102 - Disclosure - Description of Organization and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesPolicies</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>101</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R102.htm</HtmlFileName>
      <LongName>2130103 - Disclosure - Description of Organization and Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>102</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R103.htm</HtmlFileName>
      <LongName>2130203 - Disclosure - Digital Assets and Digital Assets Receivable (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDigitalAssetsAndDigitalAssetsReceivableTables</Role>
      <ShortName>Digital Assets and Digital Assets Receivable (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDigitalAssetsAndDigitalAssetsReceivable</ParentRole>
      <Position>103</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R104.htm</HtmlFileName>
      <LongName>2130403 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesTables</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>104</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R105.htm</HtmlFileName>
      <LongName>2130503 - Disclosure - Common Stock (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockTables</Role>
      <ShortName>Common Stock (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommonStock</ParentRole>
      <Position>105</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R106.htm</HtmlFileName>
      <LongName>2140101 - Disclosure - Description of Organization and Summary of Significant Accounting Policies -Organization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesOrganizationDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies -Organization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>106</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R107.htm</HtmlFileName>
      <LongName>2140102 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Liquidity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesLiquidityDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Liquidity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>107</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R108.htm</HtmlFileName>
      <LongName>2140103 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Accounts Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesAccountsReceivableDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Accounts Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>108</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R109.htm</HtmlFileName>
      <LongName>2140104 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Licensing Receivables, Physical Inventory and Prepaid Expenses and Other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesLicensingReceivablesPhysicalInventoryAndPrepaidExpensesAndOtherDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Licensing Receivables, Physical Inventory and Prepaid Expenses and Other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>109</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R110.htm</HtmlFileName>
      <LongName>2140105 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Notes Receivable (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesNotesReceivableDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Notes Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>110</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R111.htm</HtmlFileName>
      <LongName>2140106 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Deferred Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesDeferredRevenueDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Deferred Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>111</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R112.htm</HtmlFileName>
      <LongName>2140107 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Revenue Recognition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesRevenueRecognitionDetailss</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Revenue Recognition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>112</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R113.htm</HtmlFileName>
      <LongName>2140108 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesIncomeTaxesDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>113</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R114.htm</HtmlFileName>
      <LongName>2140109 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesRecentAccountingPronouncementsDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>114</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R115.htm</HtmlFileName>
      <LongName>2140201 - Disclosure - Digital Assets and Digital Assets Receivable - Digital assets receivable shown on the condensed consolidated balance sheets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDigitalAssetsAndDigitalAssetsReceivableDigitalAssetsReceivableShownOnCondensedConsolidatedBalanceSheetsDetails</Role>
      <ShortName>Digital Assets and Digital Assets Receivable - Digital assets receivable shown on the condensed consolidated balance sheets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>115</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R116.htm</HtmlFileName>
      <LongName>2140202 - Disclosure - Digital Assets and Digital Assets Receivable - Digital assets receivable shown on the condensed consolidated balance sheets - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDigitalAssetsAndDigitalAssetsReceivableDigitalAssetsReceivableShownOnCondensedConsolidatedBalanceSheetsAdditionalInformationDetails</Role>
      <ShortName>Digital Assets and Digital Assets Receivable - Digital assets receivable shown on the condensed consolidated balance sheets - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>116</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R117.htm</HtmlFileName>
      <LongName>2140301 - Disclosure - Notes Payable (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesPayableDetails</Role>
      <ShortName>Notes Payable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureNotesPayable</ParentRole>
      <Position>117</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R118.htm</HtmlFileName>
      <LongName>2140401 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesDetailsss</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>118</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R119.htm</HtmlFileName>
      <LongName>2140402 - Disclosure - Commitments and Contingencies - Maturities of operating lease liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesMaturitiesOfOperatingLeaseLiabilitiesDetails</Role>
      <ShortName>Commitments and Contingencies - Maturities of operating lease liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>119</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R120.htm</HtmlFileName>
      <LongName>2140403 - Disclosure - Commitments and Contingencies - Weighted average remaining lease terms and interest rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesWeightedAverageRemainingLeaseTermsAndInterestRatesDetails</Role>
      <ShortName>Commitments and Contingencies - Weighted average remaining lease terms and interest rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>120</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R121.htm</HtmlFileName>
      <LongName>2140501 - Disclosure - Common Stock - Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockNarrativesDetails</Role>
      <ShortName>Common Stock - Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>121</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R122.htm</HtmlFileName>
      <LongName>2140502 - Disclosure - Common Stock - Schedule of loss per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockScheduleOfLossPerShareDetails</Role>
      <ShortName>Common Stock - Schedule of loss per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>122</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R123.htm</HtmlFileName>
      <LongName>2140601 - Disclosure - Related-Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsDetails</Role>
      <ShortName>Related-Party Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsss</ParentRole>
      <Position>123</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R124.htm</HtmlFileName>
      <LongName>2140701 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventsDetailsss</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>124</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R125.htm</HtmlFileName>
      <LongName>22122200100 - Statement - Consolidated Balance Sheets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedBalanceSheetss</Role>
      <ShortName>Consolidated Balance Sheets</ShortName>
      <MenuCategory>Uncategorized</MenuCategory>
      <Position>125</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R126.htm</HtmlFileName>
      <LongName>22122200105 - Statement - Consolidated Balance Sheets (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedBalanceSheetsParentheticals</Role>
      <ShortName>Consolidated Balance Sheets (Parenthetical)</ShortName>
      <MenuCategory>Cover</MenuCategory>
      <Position>126</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R127.htm</HtmlFileName>
      <LongName>22122200200 - Statement - Consolidated Statements of Operations</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfOperationss</Role>
      <ShortName>Consolidated Statements of Operations</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>127</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R128.htm</HtmlFileName>
      <LongName>22122200300 - Statement - Consolidated Statements of Stockholder's Equity</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfStockholderSEquity</Role>
      <ShortName>Consolidated Statements of Stockholder's Equity</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>128</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R129.htm</HtmlFileName>
      <LongName>22122200400 - Statement - Consolidated Statements of Cash Flows</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/StatementConsolidatedStatementsOfCashFlowss</Role>
      <ShortName>Consolidated Statements of Cash Flows</ShortName>
      <MenuCategory>Statements</MenuCategory>
      <Position>129</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R130.htm</HtmlFileName>
      <LongName>22122210101 - Disclosure - Description of Organization and Summary of Significant Accounting Policies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciess</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>130</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R131.htm</HtmlFileName>
      <LongName>22122210201 - Disclosure - Property and Equipment</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePropertyAndEquipment</Role>
      <ShortName>Property and Equipment</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>131</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R132.htm</HtmlFileName>
      <LongName>22122210301 - Disclosure - Content</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureContent</Role>
      <ShortName>Content</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>132</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R133.htm</HtmlFileName>
      <LongName>22122210401 - Disclosure - Notes Receivable</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesReceivable</Role>
      <ShortName>Notes Receivable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>133</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R134.htm</HtmlFileName>
      <LongName>22122210501 - Disclosure - Intangible Assets</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIntangibleAssets</Role>
      <ShortName>Intangible Assets</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>134</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R135.htm</HtmlFileName>
      <LongName>22122210601 - Disclosure - Notes Payable</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesPayables</Role>
      <ShortName>Notes Payable</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>135</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R136.htm</HtmlFileName>
      <LongName>22122210701 - Disclosure - Investments in Affiliates</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInvestmentsInAffiliates</Role>
      <ShortName>Investments in Affiliates</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>136</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R137.htm</HtmlFileName>
      <LongName>22122210801 - Disclosure - Accrued Expenses</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedExpenses</Role>
      <ShortName>Accrued Expenses</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>137</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R138.htm</HtmlFileName>
      <LongName>22122210901 - Disclosure - Accrued Settlement Costs</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedSettlementCosts</Role>
      <ShortName>Accrued Settlement Costs</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>138</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R139.htm</HtmlFileName>
      <LongName>22122211001 - Disclosure - Commitments and Contingencies</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciessss</Role>
      <ShortName>Commitments and Contingencies</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>139</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R140.htm</HtmlFileName>
      <LongName>22122211101 - Disclosure - Stock Options</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptions</Role>
      <ShortName>Stock Options</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>140</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R141.htm</HtmlFileName>
      <LongName>22122211201 - Disclosure - Common Stock</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStocks</Role>
      <ShortName>Common Stock</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>141</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R142.htm</HtmlFileName>
      <LongName>22122211301 - Disclosure - Income Taxes</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesss</Role>
      <ShortName>Income Taxes</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>142</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R143.htm</HtmlFileName>
      <LongName>22122211401 - Disclosure - Related-Party Transactions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionssss</Role>
      <ShortName>Related-Party Transactions</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>143</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R144.htm</HtmlFileName>
      <LongName>22122211501 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventssss</Role>
      <ShortName>Subsequent Events</ShortName>
      <MenuCategory>Notes</MenuCategory>
      <Position>144</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R145.htm</HtmlFileName>
      <LongName>22122220102 - Disclosure - Description of Organization and Summary of Significant Accounting Policies (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesPoliciess</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies (Policies)</ShortName>
      <MenuCategory>Policies</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>145</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R146.htm</HtmlFileName>
      <LongName>22122230103 - Disclosure - Description of Organization and Summary of Significant Accounting Policies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTabless</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPolicies</ParentRole>
      <Position>146</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R147.htm</HtmlFileName>
      <LongName>22122230203 - Disclosure - Property and Equipment (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePropertyAndEquipmentTables</Role>
      <ShortName>Property and Equipment (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosurePropertyAndEquipment</ParentRole>
      <Position>147</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R148.htm</HtmlFileName>
      <LongName>22122230303 - Disclosure - Content (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureContentTables</Role>
      <ShortName>Content (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureContent</ParentRole>
      <Position>148</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R149.htm</HtmlFileName>
      <LongName>22122230503 - Disclosure - Intangible Assets (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIntangibleAssetsTables</Role>
      <ShortName>Intangible Assets (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIntangibleAssets</ParentRole>
      <Position>149</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R150.htm</HtmlFileName>
      <LongName>22122230803 - Disclosure - Accrued Expenses (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedExpensesTables</Role>
      <ShortName>Accrued Expenses (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureAccruedExpenses</ParentRole>
      <Position>150</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R151.htm</HtmlFileName>
      <LongName>22122230903 - Disclosure - Accrued Settlement Costs (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedSettlementCostsTables</Role>
      <ShortName>Accrued Settlement Costs (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureAccruedSettlementCosts</ParentRole>
      <Position>151</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R152.htm</HtmlFileName>
      <LongName>22122231003 - Disclosure - Commitments and Contingencies (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesTabless</Role>
      <ShortName>Commitments and Contingencies (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingencies</ParentRole>
      <Position>152</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R153.htm</HtmlFileName>
      <LongName>22122231103 - Disclosure - Stock Options (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsTables</Role>
      <ShortName>Stock Options (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureStockOptions</ParentRole>
      <Position>153</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R154.htm</HtmlFileName>
      <LongName>22122231203 - Disclosure - Common Stock (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockTabless</Role>
      <ShortName>Common Stock (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommonStock</ParentRole>
      <Position>154</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R155.htm</HtmlFileName>
      <LongName>22122231303 - Disclosure - Income Taxes (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesTabless</Role>
      <ShortName>Income Taxes (Tables)</ShortName>
      <MenuCategory>Tables</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIncomeTaxes</ParentRole>
      <Position>155</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R156.htm</HtmlFileName>
      <LongName>22122240101 - Disclosure - Description of Organization and Summary of Significant Accounting Policies -Organization (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesOrganizationDetailss</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies -Organization (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>156</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R157.htm</HtmlFileName>
      <LongName>22122240102 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Concentrations of credit risk (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesConcentrationsOfCreditRiskDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Concentrations of credit risk (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>157</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R158.htm</HtmlFileName>
      <LongName>22122240103 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Digital Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesDigitalAssetsDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Digital Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesTables</ParentRole>
      <Position>158</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R159.htm</HtmlFileName>
      <LongName>22122240104 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Liquidity and Cash and Cash Equivalents (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesLiquidityAndCashAndCashEquivalentsDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Liquidity and Cash and Cash Equivalents (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>159</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R160.htm</HtmlFileName>
      <LongName>22122240105 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Accounts Receivable (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesAccountsReceivableDetailss</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Accounts Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>160</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R161.htm</HtmlFileName>
      <LongName>22122240106 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Licensing Receivables ,Physical Media Inventory and Prepaid Expenses and Other (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesLicensingReceivablesPhysicalMediaInventoryAndPrepaidExpensesAndOtherDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Licensing Receivables ,Physical Media Inventory and Prepaid Expenses and Other (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>161</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R162.htm</HtmlFileName>
      <LongName>22122240107 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesPropertyAndEquipmentDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>162</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R163.htm</HtmlFileName>
      <LongName>22122240108 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Content , Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesContentIntangibleAssetsDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Content , Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>163</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R164.htm</HtmlFileName>
      <LongName>22122240109 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Deferred Financing Costs and Note Discount and Deferred Revenue (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesDeferredFinancingCostsAndNoteDiscountAndDeferredRevenueDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Deferred Financing Costs and Note Discount and Deferred Revenue (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>164</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R165.htm</HtmlFileName>
      <LongName>22122240110 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Revenue Recognition (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesRevenueRecognitionDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Revenue Recognition (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>165</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R166.htm</HtmlFileName>
      <LongName>22122240111 - Disclosure - Description of Organization and Summary of Significant Accounting Policies - Income Taxes and Recent Accounting Pronouncements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureDescriptionOfOrganizationAndSummaryOfSignificantAccountingPoliciesIncomeTaxesAndRecentAccountingPronouncementsDetails</Role>
      <ShortName>Description of Organization and Summary of Significant Accounting Policies - Income Taxes and Recent Accounting Pronouncements (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>166</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R167.htm</HtmlFileName>
      <LongName>22122240201 - Disclosure - Property and Equipment (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosurePropertyAndEquipmentDetails</Role>
      <ShortName>Property and Equipment (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosurePropertyAndEquipmentTables</ParentRole>
      <Position>167</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R168.htm</HtmlFileName>
      <LongName>22122240301 - Disclosure - Content (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureContentDetails</Role>
      <ShortName>Content (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureContentTables</ParentRole>
      <Position>168</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R169.htm</HtmlFileName>
      <LongName>22122240401 - Disclosure - Notes Receivable (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesReceivableDetails</Role>
      <ShortName>Notes Receivable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureNotesReceivable</ParentRole>
      <Position>169</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R170.htm</HtmlFileName>
      <LongName>22122240501 - Disclosure - Intangible Assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIntangibleAssetsDetails</Role>
      <ShortName>Intangible Assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIntangibleAssetsTables</ParentRole>
      <Position>170</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R171.htm</HtmlFileName>
      <LongName>22122240601 - Disclosure - Notes Payable (Details)</LongName>
      <ReportType>Notes</ReportType>
      <Role>http://www.southportone.com/role/DisclosureNotesPayableDetailss</Role>
      <ShortName>Notes Payable (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureNotesPayable</ParentRole>
      <Position>171</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R172.htm</HtmlFileName>
      <LongName>22122240701 - Disclosure - Investments in Affiliates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureInvestmentsInAffiliatesDetails</Role>
      <ShortName>Investments in Affiliates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureInvestmentsInAffiliates</ParentRole>
      <Position>172</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R173.htm</HtmlFileName>
      <LongName>22122240801 - Disclosure - Accrued Expenses (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedExpensesDetails</Role>
      <ShortName>Accrued Expenses (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureAccruedExpensesTables</ParentRole>
      <Position>173</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R174.htm</HtmlFileName>
      <LongName>22122240901 - Disclosure - Accrued Settlement Costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedSettlementCostsDetails</Role>
      <ShortName>Accrued Settlement Costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureAccruedSettlementCostsTables</ParentRole>
      <Position>174</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R175.htm</HtmlFileName>
      <LongName>22122240902 - Disclosure - Accrued Settlement Cost - Settlement cost maturities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureAccruedSettlementCostSettlementCostMaturitiesDetails</Role>
      <ShortName>Accrued Settlement Cost - Settlement cost maturities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>175</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R176.htm</HtmlFileName>
      <LongName>22122241001 - Disclosure - Commitments and Contingencies (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesDetailssss</Role>
      <ShortName>Commitments and Contingencies (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesTables</ParentRole>
      <Position>176</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R177.htm</HtmlFileName>
      <LongName>22122241002 - Disclosure - Commitments and Contingencies - Maturities of operating lease liabilities (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesMaturitiesOfOperatingLeaseLiabilitiesDetailss</Role>
      <ShortName>Commitments and Contingencies - Maturities of operating lease liabilities (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>177</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R178.htm</HtmlFileName>
      <LongName>22122241003 - Disclosure - Commitments and Contingencies - Weighted average remaining lease terms and interest rates (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommitmentsAndContingenciesWeightedAverageRemainingLeaseTermsAndInterestRatesDetailss</Role>
      <ShortName>Commitments and Contingencies - Weighted average remaining lease terms and interest rates (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>178</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R179.htm</HtmlFileName>
      <LongName>22122241101 - Disclosure - Stock Options - Stock Incentive Plan (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsStockIncentivePlanDetails</Role>
      <ShortName>Stock Options - Stock Incentive Plan (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>179</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R180.htm</HtmlFileName>
      <LongName>22122241102 - Disclosure - Stock Options - Compensation costs (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsCompensationCostsDetails</Role>
      <ShortName>Stock Options - Compensation costs (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>180</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R181.htm</HtmlFileName>
      <LongName>22122241103 - Disclosure - Stock Options - Activity (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsActivityDetails</Role>
      <ShortName>Stock Options - Activity (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>181</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R182.htm</HtmlFileName>
      <LongName>22122241104 - Disclosure - Stock Options - Exercise price ranges (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsExercisePriceRangesDetails</Role>
      <ShortName>Stock Options - Exercise price ranges (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>182</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R183.htm</HtmlFileName>
      <LongName>22122241105 - Disclosure - Stock Options - Valuation assumptions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsValuationAssumptionsDetails</Role>
      <ShortName>Stock Options - Valuation assumptions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>183</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R184.htm</HtmlFileName>
      <LongName>22122241106 - Disclosure - Stock Options - Additional information (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureStockOptionsAdditionalInformationDetails</Role>
      <ShortName>Stock Options - Additional information (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>184</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R185.htm</HtmlFileName>
      <LongName>22122241201 - Disclosure - Common Stock - Narratives (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockNarrativesDetailss</Role>
      <ShortName>Common Stock - Narratives (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>185</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R186.htm</HtmlFileName>
      <LongName>22122241202 - Disclosure - Common Stock - Schedule of loss per share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureCommonStockScheduleOfLossPerShareDetailss</Role>
      <ShortName>Common Stock - Schedule of loss per share (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>186</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R187.htm</HtmlFileName>
      <LongName>22122241301 - Disclosure - Income Taxes - provision (benefit) for income taxes, net (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesProvisionBenefitForIncomeTaxesNetDetails</Role>
      <ShortName>Income Taxes - provision (benefit) for income taxes, net (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>187</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R188.htm</HtmlFileName>
      <LongName>22122241302 - Disclosure - Income Taxes - Income tax reconciliation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesIncomeTaxReconciliationDetails</Role>
      <ShortName>Income Taxes - Income tax reconciliation (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>188</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R189.htm</HtmlFileName>
      <LongName>22122241303 - Disclosure - Income Taxes - Components of net deferred income tax assets (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesComponentsOfNetDeferredIncomeTaxAssetsDetails</Role>
      <ShortName>Income Taxes - Components of net deferred income tax assets (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <Position>189</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R190.htm</HtmlFileName>
      <LongName>22122241304 - Disclosure - Income Taxes (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureIncomeTaxesDetailss</Role>
      <ShortName>Income Taxes (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureIncomeTaxesTables</ParentRole>
      <Position>190</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R191.htm</HtmlFileName>
      <LongName>22122241401 - Disclosure - Related-Party Transactions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsDetailss</Role>
      <ShortName>Related-Party Transactions (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureRelatedPartyTransactionsss</ParentRole>
      <Position>191</Position>
    </Report>
    <Report instance="port-20250331xs4.htm">
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R192.htm</HtmlFileName>
      <LongName>22122241501 - Disclosure - Subsequent Events (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.southportone.com/role/DisclosureSubsequentEventsDetailssss</Role>
      <ShortName>Subsequent Events (Details)</ShortName>
      <MenuCategory>Details</MenuCategory>
      <ParentRole>http://www.southportone.com/role/DisclosureSubsequentEvents</ParentRole>
      <Position>192</Position>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <InputFiles>
    <File>port-20250331.xsd</File>
    <File>port-20250331_cal.xml</File>
    <File>port-20250331_def.xml</File>
    <File>port-20250331_lab.xml</File>
    <File>port-20250331_pre.xml</File>
    <File doctype="S-4/A" isDefinitelyFs="true" isUsgaap="true" original="port-20250331xs4.htm">port-20250331xs4.htm</File>
  </InputFiles>
  <SupplementalFiles>
    <File>port-20250331xs4019.jpg</File>
    <File>port-20250331xs4021.jpg</File>
    <File>port-20250331xs4022.jpg</File>
  </SupplementalFiles>
  <BaseTaxonomies>
    <BaseTaxonomy items="1">http://fasb.org/srt/2024</BaseTaxonomy>
    <BaseTaxonomy items="2277">http://fasb.org/us-gaap/2024</BaseTaxonomy>
    <BaseTaxonomy items="11">http://xbrl.sec.gov/dei/2024</BaseTaxonomy>
  </BaseTaxonomies>
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
