Investments In Unconsolidated Joint Ventures (Investments In Unconsolidated Joint Ventures) (Detail)	9 Months Ended
	Sep. 30, 2012 Property
Entity Owning Land And Infrastructure Of Project [Member]
Schedule of Equity Method Investments [Line Items]
Nominal % Ownership	33.30%
Mountain View Research And Technology Park [Member]
Schedule of Equity Method Investments [Line Items]
Nominal % Ownership	39.50%
300 Billerica Road [Member]
Schedule of Equity Method Investments [Line Items]
Nominal % Ownership	25.00%
Annapolis Junction NFM, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Annapolis Junction
Nominal % Ownership	50.00%	[1]
Number of buildings	1
Number of buildings in under construction	1
Number of Undeveloped Land Parcels	2
Square 407 Limited Partnership [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Market Square North
Nominal % Ownership	50.00%
The Metropolitan Square Associates LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Metropolitan Square
Nominal % Ownership	51.00%
BP/CRF 901 New York Avenue LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	901 New York Avenue
Nominal % Ownership	25.00%	[2]
WP Project Developer LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Wisconsin Place Land and Infrastructure
Nominal % Ownership	33.30%	[3]
RBP Joint Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Eighth Avenue and 46th Street
Nominal % Ownership	50.00%	[4]
Boston Properties Office Value-Added Fund, L.P. [Member]
Schedule of Equity Method Investments [Line Items]
Properties	300 Billerica Road and Mountain View Research and Technology Parks
Nominal % Ownership	39.50%	[2],[5]
767 Venture, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	The General Motors Building
Nominal % Ownership	60.00%
2 GCT Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	Two Grand Central Tower
Nominal % Ownership	60.00%	[6]
540 Madison Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	540 Madison Avenue
Nominal % Ownership	60.00%
125 West 55th Street Venture LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	125 West 55thStreet
Nominal % Ownership	60.00%
500 North Capitol LLC [Member]
Schedule of Equity Method Investments [Line Items]
Properties	500 North Capitol Street, NW
Nominal % Ownership	30.00%	[7]

[1] Comprised of one building, one building under construction and two undeveloped land parcels.

[2] The Company's economic ownership can increase based on the achievement of certain return thresholds.

[3] The Company's wholly-owned entity that owns the office component of the project also owns a 33.3% interest in the entity owning the land and infrastructure of the project.

[4] This property is not in operation and consists of assembled land.

[5] The Company has a 39.5% interest in the Mountain View Research and Technology Park properties. 300 Billerica Road, in which the Company had a 25.0% interest, was sold on September 27, 2012. As of September 30, 2012, the Company's investment in the Value-Added Fund included undistributed proceeds from the sale of 300 Billerica Road.

[6] The property was sold on October 25, 2011. As of September 30, 2012, the investment is comprised of working capital and a portion of undistributed sale proceeds.

[7] This property is under construction.