<?xml version="1.0" encoding="utf-8"?>
<FilingSummary xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <Version>2.4.0.8</Version>
  <ProcessingTime />
  <ReportFormat>Html</ReportFormat>
  <ContextCount>101</ContextCount>
  <ElementCount>252</ElementCount>
  <EntityCount>1</EntityCount>
  <FootnotesReported>false</FootnotesReported>
  <SegmentCount>39</SegmentCount>
  <ScenarioCount>0</ScenarioCount>
  <TuplesReported>false</TuplesReported>
  <UnitCount>6</UnitCount>
  <MyReports>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R1.htm</HtmlFileName>
      <LongName>0000 - Document - Document and Entity Information</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DocumentAndEntityInformation</Role>
      <ShortName>Document and Entity Information</ShortName>
    </Report>
    <Report>
      <IsDefault>true</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R2.htm</HtmlFileName>
      <LongName>0010 - Statement - CONSOLIDATED BALANCE SHEETS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/BalanceSheet</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R3.htm</HtmlFileName>
      <LongName>0015 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/BalanceSheetParenthetical</Role>
      <ShortName>CONSOLIDATED BALANCE SHEETS (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R4.htm</HtmlFileName>
      <LongName>0020 - Statement - CONSOLIDATED STATEMENTS OF INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/StatementOfIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R5.htm</HtmlFileName>
      <LongName>0025 - Statement - CONSOLIDATED STATEMENTS OF INCOME (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/StatementOfIncomeParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF INCOME (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R6.htm</HtmlFileName>
      <LongName>0030 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/StatementOfComprehensiveIncome</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R7.htm</HtmlFileName>
      <LongName>0040 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/StatementOfStockholdersEquity</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R8.htm</HtmlFileName>
      <LongName>0045 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/StatementOfStockholdersEquityParenthetical</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R9.htm</HtmlFileName>
      <LongName>0050 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/CashFlows</Role>
      <ShortName>CONSOLIDATED STATEMENTS OF CASH FLOWS</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R10.htm</HtmlFileName>
      <LongName>1010 - Disclosure - Organization and Background</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureOrganizationAndBackground</Role>
      <ShortName>Organization and Background</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R11.htm</HtmlFileName>
      <LongName>1020 - Disclosure - Basis of Preparation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureBasisOfPreparation</Role>
      <ShortName>Basis of Preparation</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R12.htm</HtmlFileName>
      <LongName>1030 - Disclosure - Earnings Per Common Share</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureEarningsPerCommonShare</Role>
      <ShortName>Earnings Per Common Share</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R13.htm</HtmlFileName>
      <LongName>1040 - Disclosure - Real Estate Acquisitions</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureRealEstateAcquisitions</Role>
      <ShortName>Real Estate Acquisitions</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R14.htm</HtmlFileName>
      <LongName>1050 - Disclosure - Investment in Unconsolidated Joint Ventures</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureInvestmentInUnconsolidatedJointVentures</Role>
      <ShortName>Investment in Unconsolidated Joint Ventures</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R15.htm</HtmlFileName>
      <LongName>1060 - Disclosure - Allowance for Doubtful Accounts</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureAllowanceForDoubtfulAccounts</Role>
      <ShortName>Allowance for Doubtful Accounts</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R16.htm</HtmlFileName>
      <LongName>1070 - Disclosure - Discontinued Operations and Sale of Properties</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureDiscontinuedOperationsAndSaleOfProperties</Role>
      <ShortName>Discontinued Operations and Sale of Properties</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R17.htm</HtmlFileName>
      <LongName>1080 - Disclosure - Line of Credit</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureLineOfCredit</Role>
      <ShortName>Line of Credit</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R18.htm</HtmlFileName>
      <LongName>1090 - Disclosure - Compensation and Services Agreement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureCompensationAndServicesAgreement</Role>
      <ShortName>Compensation and Services Agreement</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R19.htm</HtmlFileName>
      <LongName>1100 - Disclosure - Common Stock Cash Dividend</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureCommonStockCashDividend</Role>
      <ShortName>Common Stock Cash Dividend</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R20.htm</HtmlFileName>
      <LongName>1110 - Disclosure - Shares Issued through Equity Offering Program</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureSharesIssuedThroughEquityOfferingProgram</Role>
      <ShortName>Shares Issued through Equity Offering Program</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R21.htm</HtmlFileName>
      <LongName>1120 - Disclosure - Stock Based Compensation</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureStockBasedCompensation</Role>
      <ShortName>Stock Based Compensation</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R22.htm</HtmlFileName>
      <LongName>1130 - Disclosure - Fair Value Measurements</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurements</Role>
      <ShortName>Fair Value Measurements</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R23.htm</HtmlFileName>
      <LongName>1140 - Disclosure - New Accounting Pronouncement</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureNewAccountingPronouncement</Role>
      <ShortName>New Accounting Pronouncement</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R24.htm</HtmlFileName>
      <LongName>1150 - Disclosure - Subsequent Events</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureSubsequentEvents</Role>
      <ShortName>Subsequent Events</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R25.htm</HtmlFileName>
      <LongName>2020 - Disclosure - Basis of Preparation (Policies)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureBasisOfPreparationPolicies</Role>
      <ShortName>Basis of Preparation (Policies)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R26.htm</HtmlFileName>
      <LongName>3030 - Disclosure - Earnings Per Common Share (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureEarningsPerCommonShareTables</Role>
      <ShortName>Earnings Per Common Share (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R27.htm</HtmlFileName>
      <LongName>3040 - Disclosure - Real Estate Acquisitions (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureRealEstateAcquisitionsTables</Role>
      <ShortName>Real Estate Acquisitions (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R28.htm</HtmlFileName>
      <LongName>3070 - Disclosure - Discontinued Operations and Sale of Properties (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureDiscontinuedOperationsAndSaleOfPropertiesTables</Role>
      <ShortName>Discontinued Operations and Sale of Properties (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R29.htm</HtmlFileName>
      <LongName>3120 - Disclosure - Stock Based Compensation (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureStockBasedCompensationTables</Role>
      <ShortName>Stock Based Compensation (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R30.htm</HtmlFileName>
      <LongName>3130 - Disclosure - Fair Value Measurements (Tables)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurementsTables</Role>
      <ShortName>Fair Value Measurements (Tables)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R31.htm</HtmlFileName>
      <LongName>4010 - Disclosure - Organization and Background (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureOrganizationAndBackgroundDetails</Role>
      <ShortName>Organization and Background (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R32.htm</HtmlFileName>
      <LongName>4020 - Disclosure - Basis of Preparation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureBasisOfPreparationDetails</Role>
      <ShortName>Basis of Preparation (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R33.htm</HtmlFileName>
      <LongName>4030 - Disclosure - Earnings Per Common Share (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureEarningsPerCommonShareDetails</Role>
      <ShortName>Earnings Per Common Share (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R34.htm</HtmlFileName>
      <LongName>4040 - Disclosure - Real Estate Acquisitions (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureRealEstateAcquisitionsDetails</Role>
      <ShortName>Real Estate Acquisitions (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R35.htm</HtmlFileName>
      <LongName>4050 - Disclosure - Investment in Unconsolidated Joint Ventures (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureInvestmentInUnconsolidatedJointVenturesDetails</Role>
      <ShortName>Investment in Unconsolidated Joint Ventures (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R36.htm</HtmlFileName>
      <LongName>4060 - Disclosure - Allowance for Doubtful Accounts (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureAllowanceForDoubtfulAccountsDetails</Role>
      <ShortName>Allowance for Doubtful Accounts (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R37.htm</HtmlFileName>
      <LongName>4070 - Disclosure - Discontinued Operations and Sale of Properties (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureDiscontinuedOperationsAndSaleOfPropertiesDetails</Role>
      <ShortName>Discontinued Operations and Sale of Properties (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R38.htm</HtmlFileName>
      <LongName>4080 - Disclosure - Line of Credit (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureLineOfCreditDetails</Role>
      <ShortName>Line of Credit (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R39.htm</HtmlFileName>
      <LongName>4090 - Disclosure - Compensation and Services Agreement (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureCompensationAndServicesAgreementDetails</Role>
      <ShortName>Compensation and Services Agreement (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R40.htm</HtmlFileName>
      <LongName>4100 - Disclosure - Common Stock Cash Dividend (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureCommonStockCashDividendDetails</Role>
      <ShortName>Common Stock Cash Dividend (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R41.htm</HtmlFileName>
      <LongName>4110 - Disclosure - Shares Issued through Equity Offering Program (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureSharesIssuedThroughEquityOfferingProgramDetails</Role>
      <ShortName>Shares Issued through Equity Offering Program (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R42.htm</HtmlFileName>
      <LongName>4120 - Disclosure - Stock Based Compensation (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureStockBasedCompensationDetails</Role>
      <ShortName>Stock Based Compensation (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R43.htm</HtmlFileName>
      <LongName>4130 - Disclosure - Fair Value Measurements (Details)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurementsDetails</Role>
      <ShortName>Fair Value Measurements (Details)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R44.htm</HtmlFileName>
      <LongName>4131 - Disclosure - Fair Value Measurements (Details 2)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurementsDetails2</Role>
      <ShortName>Fair Value Measurements (Details 2)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R45.htm</HtmlFileName>
      <LongName>4132 - Disclosure - Fair Value Measurements (Details 3)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurementsDetails3</Role>
      <ShortName>Fair Value Measurements (Details 3)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <HtmlFileName>R46.htm</HtmlFileName>
      <LongName>4133 - Disclosure - Fair Value Measurements (Details 4)</LongName>
      <ReportType>Sheet</ReportType>
      <Role>http://www.onelibertyproperties.com/role/DisclosureFairValueMeasurementsDetails4</Role>
      <ShortName>Fair Value Measurements (Details 4)</ShortName>
    </Report>
    <Report>
      <IsDefault>false</IsDefault>
      <HasEmbeddedReports>false</HasEmbeddedReports>
      <LongName>All Reports</LongName>
      <ReportType>Book</ReportType>
      <ShortName>All Reports</ShortName>
    </Report>
  </MyReports>
  <Logs>
    <Log type="Info">Element us-gaap_AvailableForSaleSecuritiesEquitySecurities had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_DividendsCommonStockCash had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">Element us-gaap_FairValueInputsDiscountRate had a mix of decimals attribute values: 2 3.</Log>
    <Log type="Info">Element us-gaap_ProceedsFromSaleOfRealEstateHeldforinvestment had a mix of decimals attribute values: -3 0.</Log>
    <Log type="Info">'Monetary' elements on report '0040 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY' had a mix of different decimal attribute values.</Log>
    <Log type="Info">'Monetary' elements on report '4040 - Disclosure - Real Estate Acquisitions (Details)' had a mix of different decimal attribute values.</Log>
    <Log type="Info">Process Flow-Through: 0010 - Statement - CONSOLIDATED BALANCE SHEETS</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Mar. 31, 2013'</Log>
    <Log type="Info">	Process Flow-Through: Removing column 'Dec. 31, 2012'</Log>
    <Log type="Info">Process Flow-Through: 0015 - Statement - CONSOLIDATED BALANCE SHEETS (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 0020 - Statement - CONSOLIDATED STATEMENTS OF INCOME</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 0025 - Statement - CONSOLIDATED STATEMENTS OF INCOME (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 0030 - Statement - CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2013'</Log>
    <Log type="Info">Process Flow-Through: 0045 - Statement - CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Parenthetical)</Log>
    <Log type="Info">Process Flow-Through: 0050 - Statement - CONSOLIDATED STATEMENTS OF CASH FLOWS</Log>
    <Log type="Info">	Process Flow-Through: Removing column '12 Months Ended
Dec. 31, 2013'</Log>
  </Logs>
  <InputFiles>
    <File>olp-20140331.xml</File>
    <File>olp-20140331.xsd</File>
    <File>olp-20140331_cal.xml</File>
    <File>olp-20140331_def.xml</File>
    <File>olp-20140331_lab.xml</File>
    <File>olp-20140331_pre.xml</File>
  </InputFiles>
  <SupplementalFiles />
  <BaseTaxonomies />
  <HasPresentationLinkbase>true</HasPresentationLinkbase>
  <HasCalculationLinkbase>true</HasCalculationLinkbase>
</FilingSummary>
