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

Amount of operating lease income from lease payments paid and payable to lessor. Excludes variable lease payments not included in measurement of lease receivable. Also excludes amortization related to lease intangible assets and liabilities.

No definition available.

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

Amount of operating lease income from variable lease payments paid and payable to lessor, excluding amount included in measurement of lease receivable. Also excluding amortization related to lease intangible assets and liabilities.

No definition available.

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

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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Name:	us-gaap_AmortizationOfAboveAndBelowMarketLeases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Indicates (true false) whether practical expedient is elected to account for lease component and nonlease component as single lease component.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 3A
-Subparagraph (a)
-SubTopic 30
-Topic 842
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-3A

Name:	us-gaap_LeasePracticalExpedientLessorSingleLeaseComponent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

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

Indicates (true false) whether lessor has option to extend operating lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479773/842-30-50-3

Name:	us-gaap_LessorOperatingLeaseExistenceOfOptionToExtend
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

Indicates (true false) whether lessor has option to terminate operating lease.

Name:	us-gaap_LessorOperatingLeaseExistenceOfOptionToTerminate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.