Represents the entity share in sale price of real estate sold in unconsolidated joint venture.

No definition available.

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

- Definition

Represents the pro rata share of the amount of gain or loss resulting from sale of property by unconsolidated joint venture.

+ References

No definition available.

+ Details

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

- Details

Name:	olp_InvestmentsInUnconsolidatedJointVenturesAbstract
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- Definition

Portion of equity (net assets) in a variable interest entity (VIE) not attributable, directly or indirectly, to the parent entity. That is, this is the portion of equity in a VIE that is attributable to the other joint venture partner.

+ References

No definition available.

+ Details

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

- Definition

Represents the amount of mortgage prepayment penalty.

+ References

No definition available.

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- Definition

Represents the number of properties sold by the entity.

+ References

No definition available.

+ Details

Name:	olp_NumberOfPropertiesSold
Namespace Prefix:	olp_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the number of unconsolidated joint ventures of the entity.

+ References

No definition available.

+ Details

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

- Definition

Represents proceeds before cost of sale from disposition of unconsolidated joint venture interest.

+ References

No definition available.

+ Details

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

- Definition

The cash inflow from the sale of real estate in an unconsolidated joint venture that the reporting entity has not previously accounted for using consolidation or the equity method of accounting.

+ References

No definition available.

+ Details

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

- Definition

Sale price of real estate sold in unconsolidated joint venture.

+ References

No definition available.

+ Details

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

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the joint venture partner.

+ References

No definition available.

+ Details

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

- Definition

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

+ Details

Name:	us-gaap_GainLossOnSaleOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Definition

The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.14(d))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 14

-Subparagraph d

-Article 9

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

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 13

-Subparagraph g

-Chapter V

-Subsection II

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

+ Details

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- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: 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=6943989&loc=d3e3602-108585

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 9

-Article 5

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 6

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=16385135&loc=d3e33749-111570

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 18

-Paragraph 19

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.12)

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 11

-Article 7

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

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

+ References

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

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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Balance Type:	na
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- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 50

-Paragraph 5A

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=7880789&loc=SL6759159-111685

+ Details

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Investment in Unconsolidated Joint Ventures (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended	0 Months Ended	1 Months Ended		9 Months Ended
	Sep. 30, 2013 property	Sep. 30, 2012	Sep. 30, 2013 property item	Sep. 30, 2012	Dec. 31, 2012 item property	Apr. 16, 2013 Unconsolidated JV in Plano, Texas	Feb. 28, 2013 Unconsolidated JV in Plano, Texas	Feb. 29, 2012 Unconsolidated JV in Plano, Texas	Sep. 30, 2013 Unconsolidated JV in Los Angeles, California
Investment in Unconsolidated Joint Ventures
Number of unconsolidated joint ventures			5		7
Number of properties owned and operated by each unconsolidated joint venture	1		1		1
Investment in unconsolidated joint ventures	$ 4,984,000		$ 4,984,000		$ 19,485,000
Gain on sale of properties			4,705,000
Number of properties sold			2
Equity in earnings of unconsolidated joint ventures	122,000	268,000	513,000	1,015,000
Investment in Unconsolidated Joint Ventures
Ownership percentage in variable interest entity							90.00%	90.00%
Ownership percentage in variable interest entity of other party								10.00%
Amount contributed by other party								1,500,000
Gain from contribution of property to joint venture				319,000				319,000
Gain on disposition of real estate - unconsolidated joint venture			2,807,000						2,807,000
Proceeds before cost of sale from disposition of unconsolidated joint venture interest							13,500,000
Net proceeds from disposition of unconsolidated joint venture property									4,630,000
Gain on sale of equity interest in the joint venture						1,898,000
Sale price of real estate sold in unconsolidated joint venture									25,000,000
Entity share in sale price of real estate sold in unconsolidated joint venture									12,500,000
Mortgage prepayment penalty									$ 148,000