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Represents the number of joint ventures in which entity has controlling interest.

No definition available.

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The cash outflow associated with purchase of partner's interest in consolidated joint venture.

No definition available.

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Purchase of Non-Controlling interest in a consolidated joint venture

No definition available.

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The carrying amount of investments in consolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

No definition available.

Name:	olp_RealEstateInvestmentsConsolidatedRealEstateAndOtherJointVentures
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Data Type:	xbrli:monetaryItemType
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Decrease in noncontrolling interest (for example, but not limited to, redeeming or purchasing the interests of noncontrolling shareholders, issuance of shares (interests) by the non-wholly owned subsidiary to the parent entity for other than cash, and a buyback of shares (interest) by the non-wholly owned subsidiary from the noncontrolling interests).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=68079674&loc=SL4569655-111683

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
-Paragraph 24
-URI http://asc.fasb.org/extlink&oid=68079674&loc=SL4616395-111683

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The carrying amount of investments in unconsolidated real estate and other joint ventures not separately presented. This includes direct and indirect investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(d))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

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Name:	us-gaap_InvestmentsInAndAdvancesToAffiliatesCategorizationAxis=olp_OtherConsolidatedJointVentureMember
Namespace Prefix:
Data Type:	na
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Name:	dei_LegalEntityAxis=olp_MCBRealEstateLLCAndItsAffiliatesMember
Namespace Prefix:
Data Type:	na
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Period Type:

Name:	us-gaap_BusinessAcquisitionAxis=olp_RetailPropertyDeptfordNewJerseyMember
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