The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66011266&loc=d3e33918-111571

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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

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)
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Net rentable area for properties owned.

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The number of real estate properties owned as of the balance sheet date.

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The cash outflow from the acquisition of a piece of land, anything permanently fixed to it, including buildings, structures on it and so forth; includes real estate intended to generate income for the owner; excludes real estate acquired for use by the owner.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
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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.

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No definition available.

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Unconsolidated Joint Ventures (Details) $ in Millions	3 Months Ended		9 Months Ended
Unconsolidated Joint Ventures (Details) $ in Millions	Sep. 30, 2017 USD ($) ft² bldg	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) ft² bldg	Sep. 30, 2016 USD ($)
Cambridge Medipark Ltd [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	50.00%		50.00%
Liberty Property 19th & Arch [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	20.00%		20.00%
Joint venture, 2017 sales current quarter [Member] \| Gain on equity method investments [Member] \| Cambridge Medipark Ltd [Member] \| Disposal Group, Not Discontinued Operations [Member] \| Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests	$ 1.3
Joint venture, 2017 sales [Member] \| Gain on equity method investments [Member] \| Cambridge Medipark Ltd [Member] \| Disposal Group, Not Discontinued Operations [Member] \| Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests			$ 5.8
Joint venture, 2016 sales current quarter [Member] \| Gain on equity method investments [Member] \| Cambridge Medipark Ltd [Member] \| Disposal Group, Not Discontinued Operations [Member] \| Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests		$ 3.3
Joint venture, 2016 sales [Member] \| Gain on equity method investments [Member] \| Cambridge Medipark Ltd [Member] \| Disposal Group, Not Discontinued Operations [Member] \| Leaseholds and Leasehold Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Gain (loss) on sale of leasehold interests				$ 3.5
Joint venture, 2017 acquisitions current quarter [Member] \| Liberty Property 19th & Arch [Member] \| Building and Building Improvements [Member]
Schedule of Equity Method Investments [Line Items]
Leaseable square feet \| ft²	48,031		48,031
Number of Real Estate Properties \| bldg	1		1
Purchase price	$ 15.0