Capital Stock	9 Months Ended
Sep. 30, 2015
Equity [Abstract]
Capital Stock	Capital Stock In May 2015, the Company issued 37,375,000 shares of its Class A common stock in an underwritten public offering at a price of $22.50 per share, which included the underwriters’ exercise of their over-allotment option in full. The offering generated net proceeds of $806,500,000 after deducting underwriting discounts, commissions and other offering expenses. The Company used $386,156,000 of the net proceeds to finance the June 2015 acquisition of the Company’s partner’s 49% equity interest in seven life science office properties and two parking facilities at University Park at MIT, a mixed-use life science office campus in Cambridge, Massachusetts. Subsequent to the acquisition, the Company owns 100% of these assets. The Company used substantially all of the remaining net proceeds to retire a combination of nonrecourse mortgage debt and revolving credit facility borrowings. During the three and nine months ended September 30, 2015, the Company issued shares of Class A common stock in connection with the separate, privately negotiated exchange transactions involving a portion of the Company’s 2016, 2018 and 2020 Senior Notes. See Note D – Convertible Senior Debt for detailed information on these Class A common stock issuances, as well as the receipt of shares of Class A common stock in connection with the termination of a convertible note hedge related to the 2016 Senior Notes. In addition, during the three months ended September 30, 2015, the Company issued shares of Class A common stock to certain BCR entities in exchange of Class A Common Units pursuant to the Master Contribution Agreement. See the “Related Party Transactions” section of Note A – Accounting Policies for detailed information on this transaction.

Capital Stock

9 Months Ended

Sep. 30, 2015

In May 2015, the Company issued 37,375,000 shares of its Class A common stock in an underwritten public offering at a price of $22.50 per share, which included the underwriters’ exercise of their over-allotment option in full. The offering generated net proceeds of $806,500,000 after deducting underwriting discounts, commissions and other offering expenses. The Company used $386,156,000 of the net proceeds to finance the June 2015 acquisition of the Company’s partner’s 49% equity interest in seven life science office properties and two parking facilities at University Park at MIT, a mixed-use life science office campus in Cambridge, Massachusetts. Subsequent to the acquisition, the Company owns 100% of these assets. The Company used substantially all of the remaining net proceeds to retire a combination of nonrecourse mortgage debt and revolving credit facility borrowings.

During the three and nine months ended September 30, 2015, the Company issued shares of Class A common stock in connection with the separate, privately negotiated exchange transactions involving a portion of the Company’s 2016, 2018 and 2020 Senior Notes. See Note D – Convertible Senior Debt for detailed information on these Class A common stock issuances, as well as the receipt of shares of Class A common stock in connection with the termination of a convertible note hedge related to the 2016 Senior Notes.

In addition, during the three months ended September 30, 2015, the Company issued shares of Class A common stock to certain BCR entities in exchange of Class A Common Units pursuant to the Master Contribution Agreement. See the “Related Party Transactions” section of Note A – Accounting Policies for detailed information on this transaction.