Name:	olp_PaymentsToAcquireRealEstateExcludingAcquisitionCosts
Namespace Prefix:	olp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the real estate acquisition cost capitalized.

No definition available.

Name:	olp_RealEstateAcquisitionCostCapitalized
Namespace Prefix:	olp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 805
-SubTopic 50
-Name Accounting Standards Codification
-Section 15
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480123/805-50-15-3

Name:	us-gaap_AssetAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(a)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Amount of increase in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from new investment.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

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Name:	us-gaap_AssetAcquisitionAxis=olp_RealEstateAcquisitionsIn2024Member
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=olp_QualityCustomDistributionServicesInc.InAlbuquerqueNewMexicoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=olp_RussellEquipmentInc.InSavannahGeorgiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=olp_MultiTenantedIndustrialPropertyCouncilBluffsIowaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_AssetAcquisitionAxis=olp_RealEstateAcquisitionsIn2023Member
Namespace Prefix:
Data Type:	na
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