v2.4.0.6

Subsequent Events subsequent Events (Details) (USD $)	3 Months Ended		0 Months Ended			0 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Apr. 04, 2013 Annapolis Junction Building Seven [Member] Y	Apr. 10, 2013 One Twenty Five West Fifty-Fifth Street [Member] sqft	Apr. 25, 2013 Siz Zero One Massachusetts Avenue [Member] sqft	Apr. 01, 2013 140 Kendrick [Member]	Apr. 10, 2013 Mountain View Research [Member]	Apr. 10, 2013 Mountain View Technology [Member]	Apr. 11, 2013 3.125% Unsecured Senior Notes [Member]	Apr. 15, 2013 3.750% Exchangeable Senior Notes [Member]	Apr. 30, 2013 3.750% Exchangeable Senior Notes [Member]	Apr. 10, 2013 Mountain View Research And Technology Parks [Member]	Apr. 02, 2013 Chief Executive Officer [Member]
Subsequent Event [Line Items]
Penalty For Early Repayment Of Debt						$ 0
LTIP units issued (in shares)													24,231
MYLTIP units issued (in shares)													38,926
Non-qualified stock options issued													50,847
Debt Instrument, Description of Variable Rate Basis			LIBOR plus 1.65%
Equity Method Investment, Ownership Percentage			50.00%	60.00%
Construction Loan Facility Borrowing Capacity			22,000,000
Debt Instrument, Basis Spread on Variable Rate			1.65%
Purchase Price												233,500,000
Repayments of Secured Debt	23,687,000	150,519,000				47,600,000	90,000,000	20,000,000
Repayments of Notes Payable							8,600,000	3,700,000
Contractual Sales Price				470,000,000
Carrying Value of Debt Assumed in Sale				199,000,000
Net Rentable Area				588,000	478,000
Debt Instrument, Face Amount									500,000,000		450,000,000
Coupon/Stated Rate						7.51%			3.125%	3.75%
Senior Notes Pricing									99.379%
Effective Rate									3.279%
Maturity date			Apr. 04, 2016			Jul. 01, 2013			Sep. 01, 2023
Mortgage Loan Number Of Extension Options			2
Mortgage Loan Extension Option Years			1
Proceeds from Issuance of Unsecured Debt									$ 492,500,000
Debt instrument repurchase date by company										May 18, 2013
Put Right Expiration Date										May 13, 2013
Debt Instrument, Redemption Date										May 18, 2013
Debt instrument in connection with redemption last day to exchange notes										May 16, 2013
Debt Instrument Redemption Price Principal Percentage										100.00%

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