Aggregate approximate area of office buildings.

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- Definition

Area Owned By Real Estate Venture in Parcels Of Land Under Development

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Area owned by Real estate venture of undeveloped parcels of land (in acres).

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- Definition

Equity Method Investment, Budgeted Total Project Cost

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Maximum Percentage of Unconsolidated Equity Method Investment Ownership.

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Minimum percentage of unconsolidated equity method investment ownership.

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- Definition

Number of floors of a building

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- Definition

Number of office buildings in Real Estate Ventures.

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- Definition

Number of real estate ventures developed hotel property

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No definition available.

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Number of real estate ventures that owns buildings.

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Number of real estate ventures that owns land under development

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Number of real estate ventures that owns undeveloped land

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Number of rooms contain in one real estate venture developed as Hotel Property.

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Number of unconsolidated investments in Real Estate Ventures.

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- Definition

Student housing bed capacity

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- Definition

This element represents the carrying value of a short-term real estate loan to finance building costs. The funds are disbursed as needed or in accordance with a prearranged plan; generally, a portion of the funds is disbursed at inception and the remainder as construction progresses. The money is repaid on completion of the project, usually from the proceeds of a mortgage loan. The rate is normally higher than the prime rate, and there is usually an origination fee. The effective yield on these loans tends to be high, and the lender has a security interest in the real property. Note that there are separate concepts for the current and noncurrent portions of long-term construction loans.

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

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-Subparagraph (SX 210.5-02.19(a)(1))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20

-Article 5

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This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee.

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-Section 50

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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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This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

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This item represents the entity's ownership percentage in the investee multiplied by the investee's total equity.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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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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The cash outflow associated with the purchase of or advances to an 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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Investment in Unconsolidated Ventures Investment in Unconsolidated Ventures (Narrative) (Details) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2013 sqft Room acre Buildings Real_Estate_Ventures	Mar. 31, 2012	Dec. 31, 2012	Mar. 26, 2013 BDN Beacon Venture LLC [Member]	Mar. 31, 2013 The Grove at Cira Centre South [Member]	Jan. 25, 2013 The Grove at Cira Centre South [Member] beds acre Storey	Jan. 25, 2013 The Grove at Cira Centre South [Member] Brandywine Realty Trust [Member]	Jan. 25, 2013 The Grove at Cira Centre South [Member] Campus Crest Properties, LLC [Member]	Jan. 25, 2013 The Grove at Cira Centre South [Member] HSRE, LLC [Member] [Member]
Schedule of Equity Method Investments [Line Items]
Number of floors of a building						33
Student housing bed capacity						850
Company's share of equity (Company's Basis)	$ 184,802,000		$ 193,555,000	$ 17,000,000
Number of unconsolidated investments in Real Estate Ventures	19
Number of real estate ventures that owns buildings	14
Number of office buildings in Real Estate Ventures	52
Aggregate Approximate Area Of Office Buildings	6,400,000
Number of real estate ventures that owns undeveloped land	3
Area Owned By Real Estate Venture Of Undeveloped Parcels Of Land	24					1
Equity Method Investment, Underlying Equity in Net Assets						8,500,000
Equity Method Investment, Budgeted Total Project Cost					158,500,000
Payments to Acquire Equity Method Investments	7,039,000	12,512,000			60,700,000
Construction Loan					97,800,000
Equity Method Investment, Aggregate Cost						6,000,000
Equity Method Investment, Difference Between Carrying Amount and Underlying Equity						2,500,000
Number of real estate ventures that owns land under development	1
Area Owned By Real Estate Venture in Parcels Of Land Under Development	1
Number of real estate ventures developed hotel property	1
Number Of Rooms Contain In One Real Estate Venture Developed As Hotel Property	137
Minimum Percentage Of Unconsolidated Equity Method Investment Ownership	20.00%
Maximum Percentage Of Unconsolidated Equity Method Investment Ownership	65.00%
Guarantor Obligations, Current Carrying Value	600,000
Guarantor Obligations, Maximum Exposure, Undiscounted					$ 23,000,000
Equity Method Investment, Ownership Percentage				20.00%			30.00%	30.00%	40.00%