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Schedule III - Consolidated Real Estate and Accumulated Depreciation (Details) (USD $) | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2012 | Dec. 31, 2011
Gross Amount at Which Carried |  |  |  |
Total | $ 574,424,000 us-gaap_RealEstateGrossAtCarryingValue | 592,668,000 us-gaap_RealEstateGrossAtCarryingValue | $ 473,341,000 us-gaap_RealEstateGrossAtCarryingValue | $ 430,337,000 us-gaap_RealEstateGrossAtCarryingValue
Accumulated Depreciation | 73,060,000 us-gaap_RealEstateAccumulatedDepreciation | 77,643,000 us-gaap_RealEstateAccumulatedDepreciation | 62,816,000 us-gaap_RealEstateAccumulatedDepreciation | 54,214,000 us-gaap_RealEstateAccumulatedDepreciation
Other disclosure |  |  |  |
Number of properties held-for-sale |  | 2 olp_NumberOfPropertiesHeldForSale |  |
Impairment loss/charge | 62,000 us-gaap_ImpairmentOfLongLivedAssetsToBeDisposedOf |  |  |
Minimum |  |  |  |
Other disclosure |  |  |  |
Estimated useful lives of buildings and improvements |  | 3 years |  |
Maximum |  |  |  |
Other disclosure |  |  |  |
Estimated useful lives of buildings and improvements |  | 40 years |  |
Industrial |  |  |  |
Other disclosure |  |  |  |
Reduction to cost of land and buildings |  | 416,000 olp_ReductionToLandAndBuildingsDueToReceiptOfRentalReserveFromSeller / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember |  |
Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 292,049,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Initial Cost To Company |  |  |  |
Land |  | 168,737,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Buildings and Improvements |  | 406,492,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 17,439,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 168,737,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Buildings and Improvements |  | 423,931,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Total |  | 59,668,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Accumulated Depreciation |  | 77,643,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Other disclosure |  |  |  |
Number of properties net leased to same tenant pursuant to separate leases |  | 8 olp_RealEstateAndAccumulatedDepreciationNumberOfPropertiesNetLeasedToSameTenantUnderSeparateLeases / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Number of properties containing cross default provisions |  | 5 olp_RealEstateAndAccumulatedDepreciationNumberOfPropertiesContainingCrossDefaultProvisions / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Number of states in which properties containing cross default provisions are located |  | 7 olp_RealEstateAndAccumulatedDepreciationNumberOfStatesInWhichPropertiesContainingCrossDefaultProvisionsLocated / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Number of properties covered by one master lease and one loan secured by cross - collateralized mortgages |  | 11 olp_RealEstateAndAccumulatedDepreciationNumberOfPropertiesCoveredByOneMasterLeaseAndOneLoanSecuredByCrossCollateralizedMortgages / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Number of states in which properties covered by one master lease and one loan secured by cross - collateralized mortgages are located |  | 6 olp_RealEstateAndAccumulatedDepreciationNumberStatesInWhichPropertiesCoveredByOneMasterLeaseAndOneLoanSecuredByCrossCollateralizedMortgagesLocated / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember |  |
Real Estate in Ronkonkoma, NY | Flex |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,702,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,042,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Buildings and Improvements |  | 4,171,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 1,496,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,042,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Buildings and Improvements |  | 5,667,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Total |  | 6,709,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Accumulated Depreciation |  | 1,690,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RonkonkomaNYMember |  |
Real Estate 1 in Hauppauge, NY | Flex |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 8,326,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,952,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Buildings and Improvements |  | 10,954,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,952,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Buildings and Improvements |  | 10,954,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Total |  | 12,906,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Accumulated Depreciation |  | 3,845,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY1Member |  |
Real Estate 1 in Fort Mill, SC | Flex |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 8,996,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,840,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Buildings and Improvements |  | 12,687,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,840,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Buildings and Improvements |  | 12,687,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Total |  | 14,527,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Accumulated Depreciation |  | 512,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_FlexMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC1Member |  |
Real Estate in Tucker, GA | Health Clubs |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 4,968,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 807,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Buildings and Improvements |  | 3,027,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 3,126,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 807,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Buildings and Improvements |  | 6,153,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Total |  | 6,960,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Accumulated Depreciation |  | 1,775,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TuckerGAMember |  |
Real Estate in Hamilton, OH | Health Clubs |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 5,178,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,483,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Buildings and Improvements |  | 5,953,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,483,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Buildings and Improvements |  | 5,953,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Total |  | 7,436,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Accumulated Depreciation |  | 580,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HamiltonOHMember |  |
Real Estate in Secaucus, NJ | Health Clubs |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 9,590,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Initial Cost To Company |  |  |  |
Land |  | 5,449,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Buildings and Improvements |  | 9,873,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 5,449,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Buildings and Improvements |  | 9,873,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Total |  | 15,322,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Accumulated Depreciation |  | 507,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_HealthClubsMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SecaucusNJMember |  |
Real Estate 1 in Columbus, OH | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 435,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Buildings and Improvements |  | 1,703,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 435,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Buildings and Improvements |  | 1,703,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Total |  | 2,138,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Accumulated Depreciation |  | 606,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH1Member |  |
Real Estate in West Palm Beach, FL | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 181,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Buildings and Improvements |  | 724,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 181,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Buildings and Improvements |  | 724,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Total |  | 905,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Accumulated Depreciation |  | 293,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestPalmBeachFLMember |  |
Real Estate in New Hyde Park, NY | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 182,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Buildings and Improvements |  | 728,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 33,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 182,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Buildings and Improvements |  | 761,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Total |  | 943,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Accumulated Depreciation |  | 292,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHydeParkNYMember |  |
Real Estate in Melville, NY | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,982,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 774,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Buildings and Improvements |  | 3,029,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 975,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 774,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Buildings and Improvements |  | 4,004,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Total |  | 4,778,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Accumulated Depreciation |  | 998,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MelvilleNYMember |  |
Real Estate in Philadelphia, PA | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 5,489,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,981,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Buildings and Improvements |  | 7,668,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,981,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Buildings and Improvements |  | 7,668,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Total |  | 9,649,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Accumulated Depreciation |  | 1,893,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPAMember |  |
Real Estate in Saco, ME | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,174,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,027,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Buildings and Improvements |  | 3,623,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,027,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Buildings and Improvements |  | 3,623,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Total |  | 4,650,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Accumulated Depreciation |  | 789,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SacoMEMember |  |
Real Estate in Baltimore, MD | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 21,114,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Initial Cost To Company |  |  |  |
Land |  | 6,474,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Buildings and Improvements |  | 25,282,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 6,474,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Buildings and Improvements |  | 25,282,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Total |  | 31,756,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Accumulated Depreciation |  | 5,084,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BaltimoreMDMember |  |
Real Estate in Durham, NC | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,053,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,043,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Buildings and Improvements |  | 2,404,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,043,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Buildings and Improvements |  | 2,404,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Total |  | 3,447,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Accumulated Depreciation |  | 249,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DurhamNCMember |  |
Real Estate in Pinellas Park, FL | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,231,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Buildings and Improvements |  | 1,669,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,231,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Buildings and Improvements |  | 1,669,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Total |  | 2,900,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Accumulated Depreciation |  | 134,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PinellasParkFLMember |  |
Real Estate in Miamisburg, OH | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 822,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Initial Cost To Company |  |  |  |
Land |  | 165,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Buildings and Improvements |  | 1,348,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 165,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Buildings and Improvements |  | 1,348,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Total |  | 1,513,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Accumulated Depreciation |  | 80,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MiamisburgOHMember |  |
Real Estate in Indianapolis, IN | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 6,395,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,224,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Buildings and Improvements |  | 6,935,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,224,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Buildings and Improvements |  | 6,935,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Total |  | 8,159,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Accumulated Depreciation |  | 300,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisINMember |  |
Real Estate 2 in Fort Mill, SC | Industrial |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 26,671,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,804,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Buildings and Improvements |  | 33,650,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,804,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Buildings and Improvements |  | 33,650,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Total |  | 35,454,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Accumulated Depreciation |  | 1,543,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FortMillSC2Member |  |
Real Estate in New Hope MN | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 881,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Buildings and Improvements |  | 6,064,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 881,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Buildings and Improvements |  | 6,064,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Total |  | 6,945,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Accumulated Depreciation |  | 19,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewHopeMnMember |  |
Real Estate in Joppa MD | Industrial |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 3,805,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Buildings and Improvements |  | 8,142,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 42,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,805,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Buildings and Improvements |  | 8,184,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Total |  | 11,989,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Accumulated Depreciation |  | 115,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_IndustrialPropertyMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_JoppaMdMember |  |
Real Estate in Brooklyn, NY | Office |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 5,029,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,381,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Buildings and Improvements |  | 5,447,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 2,870,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,381,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Buildings and Improvements |  | 8,317,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Total |  | 9,698,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Accumulated Depreciation |  | 2,997,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_OfficeBuildingMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BrooklynNYMember |  |
Real Estate 1 in Greensboro, NC | Other |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 5,038,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC1Member |  |
Initial Cost To Company |  |  |  |
Buildings and Improvements |  | 8,328,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC1Member |  |
Gross Amount at Which Carried |  |  |  |
Buildings and Improvements |  | 8,328,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC1Member |  |
Total |  | 8,328,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC1Member |  |
Accumulated Depreciation |  | 5,567,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC1Member |  |
Real Estate in Round Rock, TX | Other |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 14,898,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,678,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Buildings and Improvements |  | 16,670,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,678,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Buildings and Improvements |  | 16,670,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Total |  | 18,348,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Accumulated Depreciation |  | 578,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoundRockTXMember |  |
Real Estate in Sandy Springs GA | Other |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 6,516,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SandySpringsGaMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 6,516,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SandySpringsGaMember |  |
Total |  | 6,516,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SandySpringsGaMember |  |
Real Estate 1 in Indianapolis IN | Other |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 4,500,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 3,087,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Buildings and Improvements |  | 5,225,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,087,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Buildings and Improvements |  | 5,225,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Total |  | 8,312,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Accumulated Depreciation |  | 29,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = olp_OtherRealEstateMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn1Member |  |
Real Estate in Seattle, WA | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 201,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Buildings and Improvements |  | 189,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 201,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Buildings and Improvements |  | 189,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Total |  | 390,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Accumulated Depreciation |  | 129,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeattleWAMember |  |
Real Estate in Rosenberg, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 216,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Buildings and Improvements |  | 863,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 67,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 216,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Buildings and Improvements |  | 930,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Total |  | 1,146,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Accumulated Depreciation |  | 422,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RosenbergTXMember |  |
Real Estate in Denver, CO | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,801,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Initial Cost To Company |  |  |  |
Land |  | 780,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Buildings and Improvements |  | 3,248,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 418,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 780,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Buildings and Improvements |  | 3,666,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Total |  | 4,446,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Accumulated Depreciation |  | 1,598,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DenverCOMember |  |
Real Estate in Ft. Myers, FL | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,947,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,013,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Buildings and Improvements |  | 4,054,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,013,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Buildings and Improvements |  | 4,054,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Total |  | 5,067,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Accumulated Depreciation |  | 1,837,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FtMyersFLMember |  |
Real Estate 2 in Atlanta, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,466,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 460,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Buildings and Improvements |  | 2,461,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 460,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Buildings and Improvements |  | 2,461,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Total |  | 2,921,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Accumulated Depreciation |  | 1,455,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AtlantaGA2Member |  |
Real Estate 1 in Houston, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 396,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Buildings and Improvements |  | 1,583,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 30,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 396,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Buildings and Improvements |  | 1,613,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Total |  | 2,009,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Accumulated Depreciation |  | 666,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX1Member |  |
Real Estate in Selden, NY | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,175,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 572,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Buildings and Improvements |  | 2,287,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 150,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 572,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Buildings and Improvements |  | 2,437,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Total |  | 3,009,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Accumulated Depreciation |  | 949,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SeldenNYMember |  |
Real Estate in Champaign, IL | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,793,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Initial Cost To Company |  |  |  |
Land |  | 791,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Buildings and Improvements |  | 3,165,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 274,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 791,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Buildings and Improvements |  | 3,439,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Total |  | 4,230,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Accumulated Depreciation |  | 1,289,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChampaignILMember |  |
Real Estate 1 in El Paso, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 2,821,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Buildings and Improvements |  | 11,123,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 321,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,821,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Buildings and Improvements |  | 11,444,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Total |  | 14,265,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Accumulated Depreciation |  | 4,244,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX1Member |  |
Real Estate in Lake Charles, LA | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,167,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Buildings and Improvements |  | 4,669,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 521,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,167,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Buildings and Improvements |  | 5,190,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Total |  | 6,357,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Accumulated Depreciation |  | 1,495,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LakeCharlesLAMember |  |
Real Estate in Somerville, MA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,906,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 510,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Buildings and Improvements |  | 1,993,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 24,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 510,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Buildings and Improvements |  | 2,017,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Total |  | 2,527,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Accumulated Depreciation |  | 598,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_SomervilleMAMember |  |
Real Estate in Newark, DE | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,934,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Initial Cost To Company |  |  |  |
Land |  | 935,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Buildings and Improvements |  | 3,643,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 10,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 935,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Buildings and Improvements |  | 3,653,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Total |  | 4,588,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Accumulated Depreciation |  | 1,037,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewarkDEMember |  |
Real Estate in Knoxville, TN | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,781,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Initial Cost To Company |  |  |  |
Land |  | 2,290,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Buildings and Improvements |  | 8,855,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,290,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Buildings and Improvements |  | 8,855,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Total |  | 11,145,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Accumulated Depreciation |  | 2,390,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KnoxvilleTNMember |  |
Real Estate 1 in Athens, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,978,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,130,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Buildings and Improvements |  | 4,340,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,130,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Buildings and Improvements |  | 4,340,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Total |  | 5,470,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Accumulated Depreciation |  | 1,153,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AthensGA1Member |  |
Real Estate in Onalaska, WI | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 753,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Buildings and Improvements |  | 3,099,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 753,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Buildings and Improvements |  | 3,099,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Total |  | 3,852,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Accumulated Depreciation |  | 785,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_OnalaskaWIMember |  |
Real Estate in Bastrop, LA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 993,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 378,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 378,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Total |  | 1,843,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Accumulated Depreciation |  | 297,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BastropLAMember |  |
Real Estate in Kentwood, LA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 966,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 368,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Buildings and Improvements |  | 1,425,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 368,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Buildings and Improvements |  | 1,425,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Total |  | 1,793,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Accumulated Depreciation |  | 290,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KentwoodLAMember |  |
Real Estate 1 in Monroe, LA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 993,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 378,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 378,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Total |  | 1,843,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Accumulated Depreciation |  | 297,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA1Member |  |
Real Estate 2 in Monroe, LA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 948,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 361,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Buildings and Improvements |  | 1,399,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 361,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Buildings and Improvements |  | 1,399,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Total |  | 1,760,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Accumulated Depreciation |  | 284,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroeLA2Member |  |
Real Estate in D'lberville, MS | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 966,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Initial Cost To Company |  |  |  |
Land |  | 368,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Buildings and Improvements |  | 1,425,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 368,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Buildings and Improvements |  | 1,425,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Total |  | 1,793,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Accumulated Depreciation |  | 289,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DlbervilleMSMember |  |
Real Estate in Flowood, MS | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,029,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Initial Cost To Company |  |  |  |
Land |  | 392,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Buildings and Improvements |  | 1,517,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 392,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Buildings and Improvements |  | 1,517,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Total |  | 1,909,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Accumulated Depreciation |  | 308,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FlowoodMSMember |  |
Real Estate 1 in Vicksburg, MS | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 940,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 358,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Buildings and Improvements |  | 1,385,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 358,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Buildings and Improvements |  | 1,385,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Total |  | 1,743,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Accumulated Depreciation |  | 282,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS1Member |  |
Real Estate 2 in Vicksburg, MS | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,145,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 436,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Buildings and Improvements |  | 1,689,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 436,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Buildings and Improvements |  | 1,689,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Total |  | 2,125,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Accumulated Depreciation |  | 343,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VicksburgMS2Member |  |
Real Estate in Hyannis, MA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 831,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 802,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Buildings and Improvements |  | 2,324,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 802,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Buildings and Improvements |  | 2,324,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Total |  | 3,126,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Accumulated Depreciation |  | 404,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HyannisMAMember |  |
Real Estate in Marston Mills, MA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 344,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 461,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Buildings and Improvements |  | 2,313,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 461,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Buildings and Improvements |  | 2,313,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Total |  | 2,774,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Accumulated Depreciation |  | 397,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MarstonMillsMAMember |  |
Real Estate in Everett, MA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,265,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EverettMAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,935,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EverettMAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,935,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EverettMAMember |  |
Total |  | 1,935,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EverettMAMember |  |
Real Estate in Royersford, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 19,750,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 19,538,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Buildings and Improvements |  | 3,150,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 403,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 19,538,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Buildings and Improvements |  | 3,553,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Total |  | 23,091,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Accumulated Depreciation |  | 412,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RoyersfordPAMember |  |
Real Estate in Monroeville, PA | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 450,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Buildings and Improvements |  | 863,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 450,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Buildings and Improvements |  | 863,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Total |  | 1,313,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Accumulated Depreciation |  | 100,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MonroevillePAMember |  |
Real Estate in Kansas City, MO | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 4,133,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Initial Cost To Company |  |  |  |
Land |  | 2,958,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Buildings and Improvements |  | 5,691,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,958,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Buildings and Improvements |  | 5,691,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Total |  | 8,649,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Accumulated Depreciation |  | 646,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KansasCityMOMember |  |
Real Estate 2 in Houston, TX | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,697,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,962,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Buildings and Improvements |  | 1,540,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,962,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Buildings and Improvements |  | 1,540,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Total |  | 3,502,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Accumulated Depreciation |  | 182,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX2Member |  |
Real Estate 3 in Houston, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 2,002,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Buildings and Improvements |  | 1,800,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,002,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Buildings and Improvements |  | 1,800,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Total |  | 3,802,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Accumulated Depreciation |  | 210,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX3Member |  |
Real Estate in Bolingbrook, IL | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 834,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Buildings and Improvements |  | 1,887,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 90,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 834,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Buildings and Improvements |  | 1,977,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Total |  | 2,811,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Accumulated Depreciation |  | 187,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BolingbrookILMember |  |
Real Estate in Crystal Lake, IL | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,913,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Initial Cost To Company |  |  |  |
Land |  | 615,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Buildings and Improvements |  | 1,899,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 615,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Buildings and Improvements |  | 1,899,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Total |  | 2,514,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Accumulated Depreciation |  | 207,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CrystalLakeILMember |  |
Real Estate in Niles, IL | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,245,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Initial Cost To Company |  |  |  |
Land |  | 843,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Buildings and Improvements |  | 3,485,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 843,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Buildings and Improvements |  | 3,485,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Total |  | 4,328,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Accumulated Depreciation |  | 332,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NilesILMember |  |
Real Estate in Lawrence, KS | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 134,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Buildings and Improvements |  | 938,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 134,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Buildings and Improvements |  | 938,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Total |  | 1,072,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Accumulated Depreciation |  | 67,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrenceKSMember |  |
Real Estate 2 in Greensboro, NC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,463,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,046,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Buildings and Improvements |  | 1,552,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 29,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,046,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Buildings and Improvements |  | 1,581,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Total |  | 2,627,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Accumulated Depreciation |  | 43,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNC2Member |  |
Real Estate in Highlands Ranch CO | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 2,361,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Buildings and Improvements |  | 2,924,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,361,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Buildings and Improvements |  | 2,924,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Total |  | 5,285,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Accumulated Depreciation |  | 53,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HighlandsRanchCoMember |  |
Real Estate in Woodbury MN | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,183,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,190,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Buildings and Improvements |  | 4,003,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,190,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Buildings and Improvements |  | 4,003,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Total |  | 5,193,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Accumulated Depreciation |  | 71,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WoodburyMnMember |  |
Real Estate in Cape Girardeau, MO | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,336,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Initial Cost To Company |  |  |  |
Land |  | 545,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Buildings and Improvements |  | 1,547,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 545,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Buildings and Improvements |  | 1,547,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Total |  | 2,092,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Accumulated Depreciation |  | 97,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CapeGirardeauMOMember |  |
Real Estate in Cherry Hill, NJ | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 7,389,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Initial Cost To Company |  |  |  |
Land |  | 3,584,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Buildings and Improvements |  | 2,794,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 4,866,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,584,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Buildings and Improvements |  | 7,660,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Total |  | 11,244,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Accumulated Depreciation |  | 1,067,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CherryHillNJMember |  |
Real Estate in Clemmons, NC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,410,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 2,564,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Buildings and Improvements |  | 3,293,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,564,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Buildings and Improvements |  | 3,293,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Total |  | 5,857,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Accumulated Depreciation |  | 210,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ClemmonsNCMember |  |
Real Estate in Deptford, NJ | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,924,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Initial Cost To Company |  |  |  |
Land |  | 572,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Buildings and Improvements |  | 1,779,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 705,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 572,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Buildings and Improvements |  | 2,484,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Total |  | 3,056,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Accumulated Depreciation |  | 252,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DeptfordNJMember |  |
Real Estate 4 in Houston, TX | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 4,844,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Initial Cost To Company |  |  |  |
Land |  | 3,122,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Buildings and Improvements |  | 3,767,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 52,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,122,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Buildings and Improvements |  | 3,819,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Total |  | 6,941,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Accumulated Depreciation |  | 321,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HoustonTX4Member |  |
Real Estate 2 in Hauppauge, NY | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,910,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 725,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Buildings and Improvements |  | 2,963,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 725,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Buildings and Improvements |  | 2,963,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Total |  | 3,688,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Accumulated Depreciation |  | 676,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HauppaugeNY2Member |  |
Real Estate in Palmyra, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 797,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 650,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Buildings and Improvements |  | 650,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 650,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Buildings and Improvements |  | 650,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Total |  | 1,300,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Accumulated Depreciation |  | 72,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PalmyraPAMember |  |
Real Estate 1 in Reading, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 787,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 655,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Buildings and Improvements |  | 625,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 655,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Buildings and Improvements |  | 625,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Total |  | 1,280,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Accumulated Depreciation |  | 70,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA1Member |  |
Real Estate 2 in Reading, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 775,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 618,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Buildings and Improvements |  | 643,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 618,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Buildings and Improvements |  | 643,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Total |  | 1,261,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Accumulated Depreciation |  | 73,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ReadingPA2Member |  |
Real Estate in Hanover, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 871,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 736,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Buildings and Improvements |  | 686,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 736,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Buildings and Improvements |  | 686,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Total |  | 1,422,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Accumulated Depreciation |  | 75,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_HanoverPAMember |  |
Real Estate in Gettysburg, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 893,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 754,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Buildings and Improvements |  | 704,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 754,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Buildings and Improvements |  | 704,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Total |  | 1,458,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Accumulated Depreciation |  | 77,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GettysburgPAMember |  |
Real Estate in Trexlertown, PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 759,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 800,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Buildings and Improvements |  | 439,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 800,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Buildings and Improvements |  | 439,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Total |  | 1,239,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Accumulated Depreciation |  | 48,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TrexlertownPAMember |  |
Real Estate in Island Park, NY | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,047,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,235,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Buildings and Improvements |  | 1,355,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,235,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Buildings and Improvements |  | 1,355,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Total |  | 2,590,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Accumulated Depreciation |  | 164,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IslandParkNYMember |  |
Real Estate in Carrollton, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,698,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 796,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Buildings and Improvements |  | 1,458,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 796,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Buildings and Improvements |  | 1,458,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Total |  | 2,254,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Accumulated Depreciation |  | 120,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CarrolltonGAMember |  |
Real Estate in Cartersville, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,606,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 786,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Buildings and Improvements |  | 1,346,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 786,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Buildings and Improvements |  | 1,346,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Total |  | 2,132,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Accumulated Depreciation |  | 118,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CartersvilleGAMember |  |
Real Estate 1 in Kennesaw, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,316,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 702,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Buildings and Improvements |  | 916,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 702,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Buildings and Improvements |  | 916,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Total |  | 1,618,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Accumulated Depreciation |  | 80,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA1Member |  |
Real Estate in Lawrenceville, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,263,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 866,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Buildings and Improvements |  | 899,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 866,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Buildings and Improvements |  | 899,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Total |  | 1,765,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Accumulated Depreciation |  | 100,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LawrencevilleGAMember |  |
Real Estate in Killeen, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,265,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Buildings and Improvements |  | 803,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,265,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Buildings and Improvements |  | 803,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Total |  | 2,068,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Accumulated Depreciation |  | 50,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KilleenTXMember |  |
Real Estate in Concord, NC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,647,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 999,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Buildings and Improvements |  | 1,076,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 999,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Buildings and Improvements |  | 1,076,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Total |  | 2,075,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Accumulated Depreciation |  | 45,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ConcordNCMember |  |
Real Estate in Myrtle Beach, SC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,647,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,102,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Buildings and Improvements |  | 1,161,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,102,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Buildings and Improvements |  | 1,161,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Total |  | 2,263,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Accumulated Depreciation |  | 48,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_MyrtleBeachSCMember |  |
Real Estate in Ann Arbor, MI | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,462,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,098,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Buildings and Improvements |  | 1,460,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,098,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Buildings and Improvements |  | 1,460,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Total |  | 2,558,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Accumulated Depreciation |  | 63,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AnnArborMIMember |  |
Real Estate in Greensboro, NC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,488,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,770,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Buildings and Improvements |  | 1,237,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,770,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Buildings and Improvements |  | 1,237,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Total |  | 3,007,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Accumulated Depreciation |  | 40,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GreensboroNCMember |  |
Real Estate 1 in Richmond, VA | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,680,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Buildings and Improvements |  | 1,341,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,680,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Buildings and Improvements |  | 1,341,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Total |  | 3,021,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Accumulated Depreciation |  | 42,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA1Member |  |
Real Estate 2 in Indianapolis IN | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 996,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 853,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 853,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Buildings and Improvements |  | 1,465,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Total |  | 2,318,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Accumulated Depreciation |  | 41,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_IndianapolisIn2Member |  |
Real Estate 1 in West Hartford, CT | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 2,881,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Buildings and Improvements |  | 94,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 326,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 2,881,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Buildings and Improvements |  | 420,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Total |  | 3,301,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Accumulated Depreciation |  | 61,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT1Member |  |
Real Estate 2 in West Hartford, CT | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 12,427,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 9,296,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Buildings and Improvements |  | 4,813,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 261,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 9,296,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Buildings and Improvements |  | 5,074,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Total |  | 14,370,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Accumulated Depreciation |  | 615,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WestHartfordCT2Member |  |
Real Estate 1 in Philadelphia PA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 4,626,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Initial Cost To Company |  |  |  |
Land |  | 1,793,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Buildings and Improvements |  | 5,640,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,793,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Buildings and Improvements |  | 5,640,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Total |  | 7,433,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Accumulated Depreciation |  | 32,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_PhiladelphiaPa1Member |  |
Real Estate 2 in Columbus, OH | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,445,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Buildings and Improvements |  | 5,431,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Costs Capitalized Subsequent to Acquisition |  |  |  |
Improvements |  | 350,000 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,445,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Buildings and Improvements |  | 5,781,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Total |  | 7,226,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Accumulated Depreciation |  | 2,475,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ColumbusOH2Member |  |
Real Estate in Duluth, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,757,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 778,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Buildings and Improvements |  | 3,436,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 778,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Buildings and Improvements |  | 3,436,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Total |  | 4,214,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Accumulated Depreciation |  | 748,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_DuluthGAMember |  |
Real Estate in Fayetteville, GA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,204,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 976,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Buildings and Improvements |  | 4,308,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 976,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Buildings and Improvements |  | 4,308,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Total |  | 5,284,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Accumulated Depreciation |  | 938,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_FayettevilleGAMember |  |
Real Estate in Wichita, KS | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,684,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,189,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Buildings and Improvements |  | 5,248,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,189,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Buildings and Improvements |  | 5,248,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Total |  | 6,437,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Accumulated Depreciation |  | 1,143,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_WichitaKSMember |  |
Real Estate in Lexington, KY | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,806,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Initial Cost To Company |  |  |  |
Land |  | 800,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Buildings and Improvements |  | 3,532,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 800,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Buildings and Improvements |  | 3,532,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Total |  | 4,332,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Accumulated Depreciation |  | 769,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_LexingtonKYMember |  |
Real Estate in Bluffton, SC | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,330,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Initial Cost To Company |  |  |  |
Land |  | 589,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Buildings and Improvements |  | 2,600,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 589,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Buildings and Improvements |  | 2,600,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Total |  | 3,189,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Accumulated Depreciation |  | 566,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BlufftonSCMember |  |
Real Estate in Amarillo, TX | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,948,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Initial Cost To Company |  |  |  |
Land |  | 863,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Buildings and Improvements |  | 3,810,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 863,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Buildings and Improvements |  | 3,810,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Total |  | 4,673,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Accumulated Depreciation |  | 830,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AmarilloTXMember |  |
Real Estate in Austin, TX | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 3,583,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,587,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Buildings and Improvements |  | 7,010,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,587,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Buildings and Improvements |  | 7,010,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Total |  | 8,597,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Accumulated Depreciation |  | 1,526,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_AustinTXMember |  |
Real Estate in Tyler, TX | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,328,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Initial Cost To Company |  |  |  |
Land |  | 1,031,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Buildings and Improvements |  | 4,554,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,031,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Buildings and Improvements |  | 4,554,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Total |  | 5,585,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Accumulated Depreciation |  | 991,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_TylerTXMember |  |
Real Estate in Newport News, VA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,696,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 751,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Buildings and Improvements |  | 3,316,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 751,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Buildings and Improvements |  | 3,316,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Total |  | 4,067,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Accumulated Depreciation |  | 722,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NewportNewsVAMember |  |
Real Estate 2 in Richmond, VA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,957,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Initial Cost To Company |  |  |  |
Land |  | 867,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Buildings and Improvements |  | 3,829,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 867,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Buildings and Improvements |  | 3,829,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Total |  | 4,696,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Accumulated Depreciation |  | 833,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_RichmondVA2Member |  |
Real Estate in Virginia Beach, VA | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 1,928,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Initial Cost To Company |  |  |  |
Land |  | 854,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Buildings and Improvements |  | 3,770,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 854,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Buildings and Improvements |  | 3,770,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Total |  | 4,624,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Accumulated Depreciation |  | 821,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_VirginiaBeachVAMember |  |
Real Estate in Gurnee, IL | Retail |  |  |  |
Schedule III - Consolidated Real Estate and Accumulated Depreciation |  |  |  |
Encumbrances |  | 2,398,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Initial Cost To Company |  |  |  |
Land |  | 834,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Buildings and Improvements |  | 3,635,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 834,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Buildings and Improvements |  | 3,635,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Total |  | 4,469,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Accumulated Depreciation |  | 753,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_GurneeILMember |  |
Real Estate in Naples, FL | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 3,070,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Buildings and Improvements |  | 2,846,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,070,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Buildings and Improvements |  | 2,846,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Total |  | 5,916,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Accumulated Depreciation |  | 448,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_NaplesFLMember |  |
Real Estate in Batavia, NY | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 515,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Buildings and Improvements |  | 2,061,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 515,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Buildings and Improvements |  | 2,061,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Total |  | 2,576,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Accumulated Depreciation |  | 818,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_BataviaNYMember |  |
Real Estate 2 in Kennesaw, GA | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,501,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Buildings and Improvements |  | 4,349,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,501,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Buildings and Improvements |  | 4,349,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Total |  | 5,850,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Accumulated Depreciation |  | 684,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_KennesawGA2Member |  |
Real Estate in Chicago, IL | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 3,877,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Buildings and Improvements |  | 2,256,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 3,877,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Buildings and Improvements |  | 2,256,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Total |  | 6,133,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Accumulated Depreciation |  | 355,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ChicagoILMember |  |
Real Estate in Cary, NC | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,129,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Buildings and Improvements |  | 3,736,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,129,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Buildings and Improvements |  | 3,736,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Total |  | 4,865,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Accumulated Depreciation |  | 588,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_CaryNCMember |  |
Real Estate in Eugene, OR | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,952,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Buildings and Improvements |  | 2,096,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,952,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Buildings and Improvements |  | 2,096,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Total |  | 4,048,000 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Accumulated Depreciation |  | 330,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_EugeneORMember |  |
Real Estate 2 in El Paso, TX | Retail |  |  |  |
Initial Cost To Company |  |  |  |
Land |  | 1,035,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX2Member |  |
Buildings and Improvements |  | 2,700,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX2Member |  |
Gross Amount at Which Carried |  |  |  |
Land |  | 1,035,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX2Member |  |
Buildings and Improvements |  | 2,700,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX2Member |  |
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Accumulated Depreciation |  | 425,000 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_RetailSiteMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = olp_ElPasoTX2Member |  |

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