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

The cash inflow from the net proceeds from the sale of property in unconsolidated joint venture.

No definition available.

Name:	olp_NetProceedsFromSaleOfPropertyInUnconsolidatedJointVenture
Namespace Prefix:	olp_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the number of properties owned and operated by each unconsolidated joint venture.

No definition available.

Name:	olp_NumberOfPropertiesOwnedAndOperatedByEachUnconsolidatedJointVenture
Namespace Prefix:	olp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the number of unconsolidated joint ventures of the entity that are accounted for under the equity method of accounting.

No definition available.

Name:	olp_NumberOfUnconsolidatedJointVentures
Namespace Prefix:	olp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The percentage of share of gain on sale of property in unconsolidated joint venture.

No definition available.

Name:	olp_PercentageOfShareOfGainOnSaleOfPropertyInUnconsolidatedJointVenture
Namespace Prefix:	olp_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Amount of income (loss) for proportionate share of equity method investee's income (loss).

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Name:	us-gaap_IncomeLossFromEquityMethodInvestments
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

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

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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.

No definition available.