Acres Of Land.

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Development Revenue.

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Disposition Price.

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Gross Proceeds From Transaction.

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Gross Proceeds From Transaction Received.

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Ground Lease Payments Per Year

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Office Component Placed In Service

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Placed In Service Percentage.

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Square Footage Of Signed Lease.

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Term Of Lease, Years.

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Amount of cash paid to acquire the entity.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
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The total cost of the acquired entity including the cash paid to shareholders of acquired entities, fair value of debt and equity securities issued to shareholders of acquired entities, the fair value of the liabilities assumed, and direct costs of the acquisition.

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Month, day and year when the business acquisition agreement was executed.

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Interest rate stated in the contractual debt agreement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Date when the debt instrument is scheduled to be fully repaid, which may be presented in a variety of ways (year, month and year, day, month and year, quarter, etc.).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The amount of debt that an Entity assumes in acquiring a business or in consideration for an asset received in a noncash (or part noncash) acquisition. Noncash is defined as transactions during a period that affect recognized assets or liabilities but that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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

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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 amount of square footage related to a real estate property.

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Real Estate Activity During the Six Months Ended June 30, 2011 (Narrative) (Details) (USD $)	0 Months Ended		6 Months Ended	0 Months Ended
	May 23, 2011 Anticipated Through Q3 2014 [Member] Seventy Five Ames Street [Member]	Feb. 01, 2011 Bay Colony Corporate Center [Member]	Jun. 30, 2011 Bay Colony Corporate Center [Member]	Jan. 14, 2011 Atlantic Wharf Development [Member]	Mar. 01, 2011 Pennsylvania Avenue Development [Member]	May 01, 2011 Five One Zero Madison Avenue [Member]	May 11, 2011 Two Two Two One I Street, NW Development [Member]	May 24, 2011 Two Five Zero West Fifty Fifth Street [Member]	Apr. 21, 2011 Carnegie Center [Member]	May 23, 2011 Seventy Five Ames Street [Member]
Acquisition date		February 1, 2011
Acquisition aggregate purchase price		$ 185,000,000	$ 185,000,000
Cash portion of purchase price		41,100,000
Portion of acquisition included in debt		143,900,000	143,900,000
Interest at a fixed rate		6.53%
Maturity date		Jun. 11, 2012
Square footage of real estate property		966,000		790,000	460,000	347,000	325,000	989,000	2,000,000	250,000
Square footage of signed lease								184,000
Number of real estate properties		4							16
Number of units in real estate property							335
Acres of land		58							560
Office component placed in-service (percentage)				57.00%	13.00%
Placed in-service (percentage)						16.00%
Gross proceeds from transaction										56,800,000
Gross proceeds from transaction received										47,400,000
Development revenue	9,400,000									11,400,000
Disposition price									468,000,000
Approximate proceeds per year from ground lease										$ 459,000
Term of lease (years)										99