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Represents the percentage of acquired property that is leased at the time of acquisition.

No definition available.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Amount of acquired leases acquired as part of a real property acquisition at below market lease rate with a finite life after adjustments.

No definition available.

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Namespace Prefix:	olp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Represents adjustments to finalize intangible lease assets relating to properties purchased.

No definition available.

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

Represents adjustments to finalize intangible lease liabilities relating to properties purchased.

No definition available.

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

Represents the amount of consideration transferred, as mortgage debt by the acquirer.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Represents the amount of addition, improvement, or renovation to a facility held for productive use including parking lot improvements acquired at the acquisition date.

No definition available.

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

The amount of identifiable intangible liabilities recognized as of the acquisition date.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Expense consisting of acquisition related transaction costs.

No definition available.

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

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Represents the period during which amount of rent is to be billed and received pursuant to the lease terms.

No definition available.

Name:	olp_DeferredRentReceivablePeriodDuringWhichAmountOfRentToBeBilledAndReceived
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Data Type:	xbrli:durationItemType
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Represents the amount of unbilled rent receivable written off during the period.

No definition available.

Name:	olp_DeferredRentReceivableWrittenOff
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the number of tenants in the property.

No definition available.

Name:	olp_NumberOfTenantsInProperty
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of tenant spaces at the property.

No definition available.

Name:	olp_NumberOfTenantSpacesAtTheProperty
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents the occupancy percentage on the real estate properties acquired by the entity.

No definition available.

Name:	olp_RealEstatePropertiesAcquisitionOccupancyPercentage
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 1

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16265-109275

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Amount of non-cash amortization of intangible asset (liability) for above and below market leases.

No definition available.

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

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 45

-Paragraph 2

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-Topic 350

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-Section 50

-Paragraph 2

-Subparagraph (a)(2)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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Amount of accumulated amortization of leases acquired as part of a real property acquisition at below market lease rate with a finite life.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized during the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized during the fourth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount of amortization income for leases with a finite life acquired as part of a real property acquisition at below market lease rate expected to be recognized during the second fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

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Amount after amortization of leases acquired as part of a real property acquisition at below market lease rate with a finite life.

No definition available.

Name:	us-gaap_BelowMarketLeaseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

No definition available.

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Period Type:	instant

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Amount of facility held for productive use including, but not limited to, office, production, storage and distribution facilities, acquired at the acquisition date.

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The amount of identifiable intangible assets recognized as of the acquisition date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 20

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Amount of real estate acquired, at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

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The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property, by the lessor or lessee, respectively. Such receivable is reduced by allowances attributable to, for instance, credit risk associated with a lessee.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.8)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

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-Section 35

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6453741&loc=d3e40879-112712

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 20

-Section 25

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39927-112707

Reference 4: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

-Topic 840

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Name:	us-gaap_DeferredRentReceivablesNet
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Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 30

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=26713463&loc=d3e16323-109275

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Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, resulting from a business combination.

No definition available.

Name:	us-gaap_FinitelivedIntangibleAssetsAcquired1
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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

No definition available.

Name:	us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive
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Data Type:	xbrli:monetaryItemType
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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.