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Noncontrolling Interests (Property Partnerships) (Narrative) (Details) $ in Thousands |  |  | 3 Months Ended | 6 Months Ended |
--- | --- | --- | --- | --- | ---
May 12, 2016 | Sep. 18, 2015 USD ($) ft² | Jun. 30, 2016 USD ($) | Jun. 30, 2015 USD ($) | Jun. 30, 2016 USD ($) | Jun. 30, 2015 USD ($) | Dec. 31, 2015 USD ($)
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Proceeds from sales of real estate |  |  |  |  | $ 104,816 | $ 194,821 |
Property partnerships |  |  | $ 1,552,937 |  | 1,552,937 |  | $ 1,574,400
Gains on sales of real estate |  |  | 0 | $ 0 | 67,623 | 95,084 |
505 9th Street [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Proceeds from sales of real estate |  | $ 194,600 |  |  |  |  |
Ownership Percentage by the Company |  | 50.00% |  |  |  |  |
Sale Price Of Sold Property |  | $ 318,000 |  |  |  |  |
Mortgage notes payable assigned in connection with the sale of real estate |  | $ 117,000 |  |  |  |  |
Net Rentable Area (in sf) | ft² |  | 322,000 |  |  |  |  |
Gains on sales of real estate |  | $ 199,500 |  |  |  |  |
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member] | 505 9th Street [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Proceeds from sales of real estate |  | 97,300 |  |  |  |  |
Gains on sales of real estate |  | 101,100 |  |  |  |  |
Boston Properties Limited Partnership |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Proceeds from sales of real estate |  |  |  |  | 104,816 | 194,821 |
Gains on sales of real estate |  |  | $ 0 | $ 0 | $ 69,792 | $ 95,084 |
Boston Properties Limited Partnership | 505 9th Street [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Gains on sales of real estate |  | $ 199,700 |  |  |  |  |
Salesforece Tower[Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Ownership Percentage | 5.00% |  |  |  |  |  |
Portion of project costs covered by a consteruction loan | 50.00% |  |  |  |  |  |
Portion of costs funded (in percentage) | 50.00% |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 3.00% |  |  |  |  |  |
Salesforece Tower[Member] | Boston Properties, Inc [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Costs funded (in percentage) | 2.50% |  |  |  |  |  |

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