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Equity method investment summarized financial information debt.

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Equity method investments including net liabilities.

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Guarantee obligations maximum exposure cancelled.

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Net gain (loss) on real estate venture transactions including real estate venture formation.

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The number of real estate properties sold during the period.

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Number of unconsolidated investments in Real Estate Ventures.

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Percentage of allocated gross sales value.

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Sale of ownership interest percentage.

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For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Area of land held.

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Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

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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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Amount of the entity's equity method investment which has been sold.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Revenue, comprised of base and incentive revenue derived from the management of joint ventures, managing third-party properties, or another entity's operations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Net rentable area for properties owned.

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The number of units in a real estate property owned as of the balance sheet date.

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The cash inflow associated with the sale of equity method investments, which are investments in joint ventures and entities in which the entity has an equity ownership interest normally of 20 to 50 percent and exercises significant influence.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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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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Investment in Unconsolidated Real Estate Ventures (Textual) (Details) ft² in Millions		3 Months Ended
	Jan. 31, 2017 USD ($) property	Mar. 31, 2017 USD ($) property	Mar. 31, 2016 USD ($)	Mar. 31, 2017	Mar. 31, 2017 property	Mar. 31, 2017 ft²	Mar. 31, 2017 Real_Estate_Investment	Mar. 31, 2017 a	Mar. 31, 2017 Apartment_unit	Dec. 31, 2016 USD ($)
Schedule Of Equity Method Investments [Line Items]
Management fees		$ 6,485,000	$ 5,235,000
Accounts receivable		12,099,000								$ 12,446,000
Cash proceeds after the payment of share of the debt and closing costs		27,230,000	4,812,000
Net gain on Real Estate Venture transactions		14,582,000	5,929,000
1919 Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Guarantees, maximum exposure amount		$ 88,900,000
TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Sale of ownership interest percentage	50.00%
Gross sales price	$ 100,500,000
Allocated gross sales value of ownership interest, percentage	50.00%
Guarantee obligations cancelled	$ 3,200,000
Cash proceeds after the payment of share of the debt and closing costs	27,200,000
Net gain on Real Estate Venture transactions	14,600,000
TB-BDN Plymouth Apartments [Member] \| Pennsylvania [Member]
Schedule Of Equity Method Investments [Line Items]
Construction Loan	$ 54,000,000
Office Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Properties Sold \| property		8
Multi-Family Complex [Member] \| TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Properties Sold \| property	398
Real Estate Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Management fees		$ 1,500,000	$ 1,500,000
Accounts receivable		1,600,000								$ 1,400,000
Unconsolidated Real Estate Ventures [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							13
Equity Method Investments including net liabilities		264,900,000
Real estate ventures aggregate indebtedness to third parties		953,800,000
Unconsolidated Real Estate Ventures [Member] \| TB-BDN Plymouth Apartments [Member]
Schedule Of Equity Method Investments [Line Items]
Equity in income (loss) of Real Estate Ventures	$ 12,600,000
Unconsolidated Real Estate Ventures [Member] \| Minimum [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage				20.00%
Unconsolidated Real Estate Ventures [Member] \| Maximum [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method investment percentage				70.00%
Unconsolidated Real Estate Ventures [Member] \| Seven Real Estate Ventures [Member] \| Office Properties [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							7
Rentable Square Feet \| ft²						8.0
Unconsolidated Real Estate Ventures [Member] \| Two Real Estate Ventures [Member] \| Undeveloped Land [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							2
Acreage of land \| a								4.3
Unconsolidated Real Estate Ventures [Member] \| Two Other Real Estate Ventures [Member] \| Under Active Development Land [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							2
Acreage of land \| a								1.4
Unconsolidated Real Estate Ventures [Member] \| Two Other Real Estate Ventures [Member] \| Residential Tower One [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							1
Number of Property units					345				345
Unconsolidated Real Estate Ventures [Member] \| Two Other Real Estate Ventures [Member] \| Residential Tower Two [Member]
Schedule Of Equity Method Investments [Line Items]
Number of Unconsolidated Investments in Real Estate Ventures \| Real_Estate_Investment							1
Number of Property units					321				321
evo at Cira Centre South Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Guarantees, maximum exposure amount		55,400,000
PJP VII [Member]
Schedule Of Equity Method Investments [Line Items]
Guarantees, maximum exposure amount		$ 400,000