Subsequent Events	9 Months Ended
Sep. 30, 2012
Subsequent Events	14. Subsequent Events On October 1, 2012, a joint venture in which the Company has a 30% interest partially placed in-service 500 North Capitol Street, NW, a Class A office redevelopment project with approximately 232,000 net rentable square feet located in Washington, DC. On October 4, 2012, the Company completed the formation of a joint venture, which owns and operates Fountain Square located in Reston, Virginia, adjacent to the Company’s other Reston properties. Fountain Square is an office and retail complex aggregating approximately 764,000 net rentable square feet, comprised of approximately 522,000 net rentable square feet of Class A office space and approximately 242,000 net rentable square feet of retail space. The joint venture partner contributed the property valued at approximately $385.0 million and related mortgage indebtedness totaling approximately $211.3 million for a 50% interest in the joint venture. The Company contributed cash totaling approximately $87.0 million for its 50% interest, which cash was distributed to the joint venture partner. The Company is consolidating this joint venture. The mortgage loan bears interest at fixed rate of 5.71% per annum and matures on October 11, 2016. Pursuant to the joint venture agreement (i) the Company has rights to acquire the partner’s 50% interest and (ii) the partner has the right to cause the Company to acquire the partner’s interest on January 4, 2016, in each case at a fixed price totaling approximately $102.0 million in cash. The fixed price option rights expire on January 31, 2016. On October 19, 2012, the Company formed a joint venture to pursue the acquisition of land in San Francisco, California which could support a 61-story, 1.4 million square foot office tower known as Transbay Tower. The purchase price for the land is approximately $190.0 million. The Company has a 50% interest in the joint venture. There can be no assurance that the acquisition will be consummated on the terms currently contemplated or at all. On October 29, 2012, the Company entered into an agreement to sell its 164 Lexington Road property for approximately $3.2 million. 164 Lexington Road is an approximately 64,000 net rentable Office/Technical property located in Billerica, Massachusetts. There can be no assurance that the sale will be consummated on the terms currently contemplated or at all. On November 8, 2012, the Company declared a dividend of $0.65 per share of common stock for the period from October 1, 2012 to December 31, 2012, payable on January 29, 2013 to shareholders of record as of the close of business on December 31, 2012.

14. Subsequent Events

On October 1, 2012, a joint venture in which the Company has a 30% interest partially placed in-service 500 North Capitol Street, NW, a Class A office redevelopment project with approximately 232,000 net rentable square feet located in Washington, DC.

On October 4, 2012, the Company completed the formation of a joint venture, which owns and operates Fountain Square located in Reston, Virginia, adjacent to the Company’s other Reston properties. Fountain Square is an office and retail complex aggregating approximately 764,000 net rentable square feet, comprised of approximately 522,000 net rentable square feet of Class A office space and approximately 242,000 net rentable square feet of retail space. The joint venture partner contributed the property valued at approximately $385.0 million and related mortgage indebtedness totaling approximately $211.3 million for a 50% interest in the joint venture. The Company contributed cash totaling approximately $87.0 million for its 50% interest, which cash was distributed to the joint venture partner. The Company is consolidating this joint venture. The mortgage loan bears interest at fixed rate of 5.71% per annum and matures on October 11, 2016. Pursuant to the joint venture agreement (i) the Company has rights to acquire the partner’s 50% interest and (ii) the partner has the right to cause the Company to acquire the partner’s interest on January 4, 2016, in each case at a fixed price totaling approximately $102.0 million in cash. The fixed price option rights expire on January 31, 2016.

On October 19, 2012, the Company formed a joint venture to pursue the acquisition of land in San Francisco, California which could support a 61-story, 1.4 million square foot office tower known as Transbay Tower. The purchase price for the land is approximately $190.0 million. The Company has a 50% interest in the joint venture. There can be no assurance that the acquisition will be consummated on the terms currently contemplated or at all.

On October 29, 2012, the Company entered into an agreement to sell its 164 Lexington Road property for approximately $3.2 million. 164 Lexington Road is an approximately 64,000 net rentable Office/Technical property located in Billerica, Massachusetts. There can be no assurance that the sale will be consummated on the terms currently contemplated or at all.

On November 8, 2012, the Company declared a dividend of $0.65 per share of common stock for the period from October 1, 2012 to December 31, 2012, payable on January 29, 2013 to shareholders of record as of the close of business on December 31, 2012.