3.25.0.1 html 94 227 1 false 38 0 false 12 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Consolidated Balance Sheets Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_StatementConsolidatedBalanceSheets Consolidated Balance Sheets Statements 2 false false R3.htm 100020 - Statement - Consolidated Balance Sheets (Parenthetical) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_StatementConsolidatedBalanceSheetsParenthetical Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100040 - Statement - Consolidated Statements of Income and Retained Earnings Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_StatementConsolidatedStatementsOfIncomeAndRetainedEarnings Consolidated Statements of Income and Retained Earnings Statements 4 false false R5.htm 100050 - Statement - Consolidated Statements of Income and Retained Earnings (Parenthetical) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_StatementConsolidatedStatementsOfIncomeAndRetainedEarningsParenthetical Consolidated Statements of Income and Retained Earnings (Parenthetical) Statements 5 false false R6.htm 100060 - Statement - Consolidated Statements of Cash Flows Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlows Consolidated Statements of Cash Flows Statements 6 false false R7.htm 995410 - Disclosure - Pay vs Performance Disclosure Sheet http://xbrl.sec.gov/ecd/role/PvpDisclosure Pay vs Performance Disclosure Notes 7 false false R8.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 8 false false R9.htm 995455 - Disclosure - Cybersecurity Risk Management, Strategy and Governance Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureCybersecurityRiskManagementStrategyAndGovernance Cybersecurity Risk Management, Strategy and Governance Notes 9 false false R10.htm 995465 - Disclosure - Description of business Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureDescriptionOfBusiness Description of business Notes 10 false false R11.htm 995475 - Disclosure - Summary of significant accounting policies Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies Summary of significant accounting policies Notes 11 false false R12.htm 995485 - Disclosure - Investments Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureInvestments Investments Notes 12 false false R13.htm 995495 - Disclosure - Properties and equipment Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosurePropertiesAndEquipment Properties and equipment Notes 13 false false R14.htm 995505 - Disclosure - Liabilities, other Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureLiabilitiesOther Liabilities, other Notes 14 false false R15.htm 995515 - Disclosure - Notes Payable Notes http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureNotesPayable Notes Payable Notes 15 false false R16.htm 995525 - Disclosure - Description of leasing arrangements Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangements1 Description of leasing arrangements Notes 16 false false R17.htm 995535 - Disclosure - Income taxes, continuing operations Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperations Income taxes, continuing operations Notes 17 false false R18.htm 995545 - Disclosure - Discontinued operations and environmental incident and subsequent event Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDiscontinuedOperationsAndEnvironmentalIncidentAndSubsequentEvent1 Discontinued operations and environmental incident and subsequent event Notes 18 false false R19.htm 995555 - Disclosure - Segment information Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureSegmentInformation1 Segment information Notes 19 false false R20.htm 995565 - Disclosure - Subsequent event Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureSubsequentEvent Subsequent event Notes 20 false false R21.htm 995575 - Disclosure - Summary of significant accounting policies (Policies) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of significant accounting policies (Policies) Policies 21 false false R22.htm 995585 - Disclosure - Properties and equipment (Tables) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosurePropertiesAndEquipmentTables Properties and equipment (Tables) Tables http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosurePropertiesAndEquipment 22 false false R23.htm 995595 - Disclosure - Liabilities, other (Tables) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureLiabilitiesOtherTables Liabilities, other (Tables) Tables http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureLiabilitiesOther 23 false false R24.htm 995605 - Disclosure - Description of leasing arrangements (Tables) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangementsTables Description of leasing arrangements (Tables) Tables http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangements1 24 false false R25.htm 995615 - Disclosure - Income taxes, continuing operations (Tables) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperationsTables Income taxes, continuing operations (Tables) Tables http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperations 25 false false R26.htm 995625 - Disclosure - Segment information (Tables) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureSegmentInformationTables Segment information (Tables) Tables http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureSegmentInformation1 26 false false R27.htm 995635 - Disclosure - Description of Business - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfBusinessAdditionalInformationDetail Description of Business - Additional Information (Detail) Details 27 false false R28.htm 995645 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetail Summary of Significant Accounting Policies - Additional Information (Detail) Details 28 false false R29.htm 995655 - Disclosure - Investments - Additional Information (Details) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureInvestmentsAdditionalInformationDetails Investments - Additional Information (Details) Details 29 false false R30.htm 995665 - Disclosure - Properties and Equipment - Properties and Equipment (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosurePropertiesAndEquipmentPropertiesAndEquipmentDetail Properties and Equipment - Properties and Equipment (Detail) Details 30 false false R31.htm 995675 - Disclosure - Liabilities, Other - Summary of Liabilities, Other (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureLiabilitiesOtherSummaryOfLiabilitiesOtherDetail Liabilities, Other - Summary of Liabilities, Other (Detail) Details 31 false false R32.htm 995685 - Disclosure - Note Payable - Revolving Credit Line - Additional Information (Details) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureNotePayableRevolvingCreditLineAdditionalInformationDetails Note Payable - Revolving Credit Line - Additional Information (Details) Details 32 false false R33.htm 995695 - Disclosure - Description of leasing arrangements - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangementsAdditionalInformationDetail Description of leasing arrangements - Additional Information (Detail) Details 33 false false R34.htm 995705 - Disclosure - Description of leasing arrangements - Minimum Future Contractual Rental Payments to be Received (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangementsMinimumFutureContractualRentalPaymentsToBeReceivedDetail Description of leasing arrangements - Minimum Future Contractual Rental Payments to be Received (Detail) Details 34 false false R35.htm 995715 - Disclosure - Description of leasing arrangements - Company's Revenue from Major Tenants (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDescriptionOfLeasingArrangementsCompanysRevenueFromMajorTenantsDetail Description of leasing arrangements - Company's Revenue from Major Tenants (Detail) Details 35 false false R36.htm 995725 - Disclosure - Income Taxes, Continuing Operations - Summary of Income Tax Expense from Continuing Operations (Details) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureIncomeTaxesContinuingOperationsSummaryOfIncomeTaxExpenseFromContinuingOperationsDetails Income Taxes, Continuing Operations - Summary of Income Tax Expense from Continuing Operations (Details) Details 36 false false R37.htm 995735 - Disclosure - Income Taxes, Continuing Operations - Reconciliation of Income Tax Provision from Continuing Operations (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperationsReconciliationOfIncomeTaxProvisionFromContinuingOperationsDetail Income Taxes, Continuing Operations - Reconciliation of Income Tax Provision from Continuing Operations (Detail) Details 37 false false R38.htm 995745 - Disclosure - Income Taxes, Continuing Operations - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperationsAdditionalInformationDetail Income Taxes, Continuing Operations - Additional Information (Detail) Details 38 false false R39.htm 995755 - Disclosure - Income Taxes, Continuing Operations - Deferred Tax Assets and Liabilities (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureIncomeTaxesContinuingOperationsDeferredTaxAssetsAndLiabilitiesDetail Income Taxes, Continuing Operations - Deferred Tax Assets and Liabilities (Detail) Details 39 false false R40.htm 995765 - Disclosure - Discontinued Operations and Environmental Incident and Subsequent Event - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureDiscontinuedOperationsAndEnvironmentalIncidentAndSubsequentEventAdditionalInformationDetail Discontinued Operations and Environmental Incident and Subsequent Event - Additional Information (Detail) Details 40 false false R41.htm 995775 - Disclosure - Segment information - Summary of Information used by the CODM for Making Operating Decisions and Assessing the Performance of Leasing Segment (Details) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureSegmentInformationSummaryOfInformationUsedByTheCodmForMakingOperatingDecisionsAndAssessingThePerformanceOfLeasingSegmentDetails Segment information - Summary of Information used by the CODM for Making Operating Decisions and Assessing the Performance of Leasing Segment (Details) Details 41 false false R42.htm 995785 - Disclosure - Segment Information - Additional Information (Details) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/DisclosureSegmentInformationAdditionalInformationDetails Segment Information - Additional Information (Details) Details 42 false false R43.htm 995795 - Disclosure - Subsequent Event - Additional Information (Detail) Sheet http://capitalpropertiesinc.com/20241231/taxonomy/role/Role_DisclosureSubsequentEventAdditionalInformationDetail Subsequent Event - Additional Information (Detail) Details 43 false false All Reports Book All Reports cptp-20241231.htm cptp-20241231.xsd http://fasb.org/us-gaap/2024 http://xbrl.sec.gov/cyd/2024 http://xbrl.sec.gov/dei/2024 http://xbrl.sec.gov/ecd/2024 false false