Total anticipated cost of investment in assets including but not limited to assets under construction.

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Anticipated balance in investment in unconsolidated joint ventures after development is completed.

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Number of Residential Condominium Units

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Number of equity method investments

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Number of hotel rooms in a hotel

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Number of stories in a high-rise building

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The current amount of expenditures for a real estate project that has not yet been completed.

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For an unclassified balance sheet, amounts due from related parties including affiliates, employees, joint ventures, officers and stockholders, immediate families thereof, and pension funds.

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Carrying amount as of the balance sheet date of obligations due all related parties.

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

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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.

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Total investments in (A) an entity in which the entity has significant influence, but does not have control, (B) subsidiaries that are not required to be consolidated and are accounted for using the equity and or cost method, and (C) an entity in which the reporting entity shares control of the entity with another party or group. Includes long-term advances receivable from a party that is affiliated with the reporting entity by means of direct or indirect ownership.

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Net rentable area for properties owned.

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Investments in Unconsolidated Joint Ventures (Liberty Property 18th & Arch LP and Liberty Property 18th & Arch Hotel, LP) (Details) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) ft² condominium_unit	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Jun. 30, 2014 USD ($) ft² room story investment
Schedule of Equity Method Investments [Line Items]
Maximum exposure to loss	$ 245,078	$ 218,454
Development in progress	267,450	360,948
Gain (loss) on sale of properties	219,270	100,314	$ 91,778
Liberty Property 18th & Arch [Member]
Schedule of Equity Method Investments [Line Items]
Maximum exposure to loss	133,000
Philadelphia [Member] \| Liberty Property 18th & Arch [Member]
Schedule of Equity Method Investments [Line Items]
Number of equity method investments \| investment				2
Anticipated investment in joint ventures				$ 186,000
Ownership percentage				20.00%
Development in progress	$ 671,000
Philadelphia [Member] \| Construction in Progress [Member] \| Liberty Property 18th & Arch [Member]
Schedule of Equity Method Investments [Line Items]
Number of stories in a high-rise building \| story				59
Leaseable square feet \| ft²				1,300
Number of hotel rooms \| room				222
Anticipated aggregate investment				$ 932,000
Liberty Property 18th & Arch [Member]
Schedule of Equity Method Investments [Line Items]
Leaseable square feet \| ft²	15
Number of Residential Condominium Units \| condominium_unit	3
Proceeds from sale of property	$ 14,300
Gain (loss) on sale of properties	300
Liberty Property 18th & Arch [Member] \| Equity Method Investee [Member] \| Prepaid Expenses and Other Current Assets [Member] \| Philadelphia [Member]
Schedule of Equity Method Investments [Line Items]
Due from related parties	1,300
Liberty Property 18th & Arch [Member] \| Equity Method Investee [Member] \| Other Liabilities [Member] \| Philadelphia [Member]
Schedule of Equity Method Investments [Line Items]
Due to related parties		1,200
Liberty Property 18th & Arch [Member] \| Equity Method Investee [Member] \| Other Income [Member] \| Philadelphia [Member]
Schedule of Equity Method Investments [Line Items]
Revenue from related parties	$ 4,800	$ 5,100	$ 1,800