Investments in Unconsolidated Entities	3 Months Ended
Mar. 31, 2012
Investments in Unconsolidated Entities [Abstract]
Investments in Unconsolidated Entities	7. Investments in Unconsolidated Entities During the year ended December 31, 2010, we entered into a joint venture investment with Forest City Enterprises (NYSE:FCE.A and FCE.B). We acquired a 49% interest in a seven-building life science campus located at University Park in Cambridge, Massachusetts, which is immediately adjacent to the campus of the Massachusetts Institute of Technology. In connection with these transactions, we invested $174,692,000 of cash which was recorded as an investment in unconsolidated entities on the balance sheet. The results of operations for these properties have been included in our consolidated results of operations from the date of acquisition by the joint venture and are reflected in our statement of comprehensive income as income from unconsolidated entities. The aggregate remaining unamortized basis difference of our investment in this joint venture of $4,818,000 at March 31, 2012 is primarily attributable to real estate and related intangible assets and will be amortized over the life of the related properties and included in the reported amount of income from unconsolidated entities. In addition, at March 31, 2012, we had other investments in unconsolidated entities with our ownership ranging from 10% to 50%.

- Definition

Equity investment disclosure, or group of investments for which combined disclosure is appropriate, including: (a) the name of each investee and percentage of ownership of common stock, (b) accounting policies for investments in common stock, (c) difference between the amount at which the investment is carried and the amount of underlying equity in net assets and the accounting treatment of the difference, (d) the total fair value of each identified investment for which a market value is available, (e) summarized information as to assets, liabilities, and results of operations of the investees (for investments in unconsolidated subsidiaries, common stock of joint ventures, or other investments using the equity method), and (f) material effects of possible conversions, exercises, or contingent issuances of the investee. Other disclosures include (a) the names of any investee in which the investor owns 20 percent or more of the voting stock and investment is not accounted for using the equity method, and the reasons why not, and (b) the names of any investee in which the investor owns less than 20% of the voting stock and the investment is accounted for using the equity method, and the reasons why it is.

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