Mortgage Notes Payable	9 Months Ended
Sep. 30, 2011
Mortgage Notes Payable [Abstract]
Mortgage Notes Payable	5. Mortgage Notes Payable On January 12, 2011, the Company notified the master servicer of the non-recourse mortgage loan collateralized by its Montvale Center property located in Gaithersburg, Maryland that the cash flows generated from the property were insufficient to fund debt service payments and capital improvements necessary to lease and operate the property and that the Company was not prepared to fund any cash shortfalls. Accordingly, at the request of the Company, the loan has been placed with the special servicer. The Company is not current on making debt service payments and is currently in default. The Company is currently accruing interest at the default interest rate of 9.93% per annum. On February 1, 2011, in connection with the Company's acquisition of Bay Colony Corporate Center in Waltham, Massachusetts, the Company assumed the mortgage loan collateralized by the property totaling approximately $143.9 million. The assumed debt is a securitized senior mortgage loan that requires interest-only payments with a balloon payment due at maturity. The assumed mortgage loan, which bears contractual interest at a fixed rate of 6.53% per annum and matures on June 11, 2012, was recorded at its fair value of approximately $149.2 million using an effective interest rate of 3.75% per annum. On May 11, 2011, the Company refinanced at maturity its mortgage loan collateralized by its 601 Lexington Avenue property located in New York City totaling approximately $453.3 million utilizing the proceeds of a draw under its Unsecured Line of Credit, which borrowing was secured by a mortgage on the property. The mortgage loan bore interest at a fixed rate of 7.19% per annum. On August 19, 2011, the Company obtained mortgage financing totaling $725.0 million collateralized by 601 Lexington Avenue. The mortgage loan bears interest at a fixed rate of 4.75% per annum and matures on April 10, 2022. Proceeds from the mortgage financing were used to repay the borrowing under the Company's Operating Partnership's Unsecured Line of Credit totaling approximately $453.3 million. The additional cash proceeds were used to refinance the $267.5 million mortgage loan collateralized by the Company's 510 Madison Avenue property located in New York City. In connection with the refinancing, the lien of the 510 Madison Avenue mortgage was spread to 601 Lexington Avenue and released from 510 Madison Avenue so that 510 Madison Avenue is no longer encumbered by any mortgage debt.

5. Mortgage Notes Payable

On January 12, 2011, the Company notified the master servicer of the non-recourse mortgage loan collateralized by its Montvale Center property located in Gaithersburg, Maryland that the cash flows generated from the property were insufficient to fund debt service payments and capital improvements necessary to lease and operate the property and that the Company was not prepared to fund any cash shortfalls. Accordingly, at the request of the Company, the loan has been placed with the special servicer. The Company is not current on making debt service payments and is currently in default. The Company is currently accruing interest at the default interest rate of 9.93% per annum.

On February 1, 2011, in connection with the Company's acquisition of Bay Colony Corporate Center in Waltham, Massachusetts, the Company assumed the mortgage loan collateralized by the property totaling approximately $143.9 million. The assumed debt is a securitized senior mortgage loan that requires interest-only payments with a balloon payment due at maturity. The assumed mortgage loan, which bears contractual interest at a fixed rate of 6.53% per annum and matures on June 11, 2012, was recorded at its fair value of approximately $149.2 million using an effective interest rate of 3.75% per annum.

On May 11, 2011, the Company refinanced at maturity its mortgage loan collateralized by its 601 Lexington Avenue property located in New York City totaling approximately $453.3 million utilizing the proceeds of a draw under its Unsecured Line of Credit, which borrowing was secured by a mortgage on the property. The mortgage loan bore interest at a fixed rate of 7.19% per annum.

On August 19, 2011, the Company obtained mortgage financing totaling $725.0 million collateralized by 601 Lexington Avenue. The mortgage loan bears interest at a fixed rate of 4.75% per annum and matures on April 10, 2022. Proceeds from the mortgage financing were used to repay the borrowing under the Company's Operating Partnership's Unsecured Line of Credit totaling approximately $453.3 million. The additional cash proceeds were used to refinance the $267.5 million mortgage loan collateralized by the Company's 510 Madison Avenue property located in New York City. In connection with the refinancing, the lien of the 510 Madison Avenue mortgage was spread to 601 Lexington Avenue and released from 510 Madison Avenue so that 510 Madison Avenue is no longer encumbered by any mortgage debt.