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Expected Total Joint Venture Development Cost

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Length of Lease

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Represents RSF occupied as a percentage of total RSF

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The amount of rentable square feet related to real estate operating properties.

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Area of a real estate property.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Minimum contractual interest rate for funds borrowed, under the debt agreement.

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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 element represents the current and noncurrent portions of a long-term real estate loan with an initial maturity beyond one year or beyond the normal operating cycle, if longer, 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 (generally one to seven years), 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.

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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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Investments in real estate, net Investment in unconsolidated joint ventures (Details) $ in Thousands	1 Months Ended	9 Months Ended
	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) ft² Extension_Option Rate	Dec. 31, 2014 USD ($)
Schedule of Equity Method Investments [Line Items]
Area of Real Estate Property \| ft²		19,943,739
Payments to acquire real estate property		$ 438,100
Equity Method Investments		$ 126,471	$ 117,406
Secured Debt from Bank Maturing on 1 April 2017 [Member]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Number of One-Year Maturity Date Extension Option \| Extension_Option		2
Longwood [Member] \| Greater Boston market
Schedule of Equity Method Investments [Line Items]
Area of Real Estate Property \| ft²		413,536
Expected Total Joint Venture Development Cost		$ 350,000
Real estate occupancy percentage		63.00%
Rentable Square Footage of Real Estate Property, Operating Properties \| ft²		259,859
Equity Method Investments		$ 50,400
Longwood [Member] \| Greater Boston market \| Equity Method Investee
Schedule of Equity Method Investments [Line Items]
Equity interest percentage (in percent)		27.50%
Longwood [Member] \| Construction Loan, Type [Domain]
Schedule of Equity Method Investments [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum		5.25%
Longwood [Member] \| Aggregate Commitments [Member] \| Greater Boston market
Schedule of Equity Method Investments [Line Items]
Long-term Construction Loan		$ 213,200
Longwood [Member] \| Outstanding Balance [Member] \| Greater Boston market
Schedule of Equity Method Investments [Line Items]
Long-term Construction Loan		175,300
Longwood [Member] \| Remaining Commitments [Member] \| Greater Boston market
Schedule of Equity Method Investments [Line Items]
Long-term Construction Loan		$ 37,900
1455/1515 Third Street [Member] \| San Franciso Bay Area [Member]
Schedule of Equity Method Investments [Line Items]
Real estate occupancy percentage \| Rate		100.00%
Length of Lease		15 years
Equity Method Investments		$ 76,100
1455/1515 Third Street [Member] \| San Franciso Bay Area [Member]
Schedule of Equity Method Investments [Line Items]
Area of Real Estate Property \| ft²		422,980
Payments to acquire real estate property	$ 125,000
Alexandria [Member] \| 1455/1515 Third Street [Member] \| San Franciso Bay Area [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest percentage (in percent)		51.00%
Uber Technologies, Inc. [Member] \| 1455/1515 Third Street [Member] \| San Franciso Bay Area [Member]
Schedule of Equity Method Investments [Line Items]
Equity interest percentage (in percent)		49.00%
LIBOR \| Longwood [Member] \| Construction Loans [Member]
Schedule of Equity Method Investments [Line Items]
Applicable margin (as a percent)		3.75%