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Noncontrolling Interests (Property Partnerships) (Narrative) (Details) $ in Thousands |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
May 12, 2016 | Sep. 18, 2015 USD ($) ft² | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Jun. 06, 2017 USD ($) | Dec. 10, 2015 USD ($)
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Property partnerships |  |  | $ 1,683,760 | $ 1,530,647 |  |  |
Proceeds from sales of real estate |  |  | 29,810 | 122,750 | $ 602,600 |  |
Gains on sales of real estate |  |  | 7,663 | 80,606 | 375,895 |  |
505 9th Street [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Ownership Percentage by Parent |  | 50.00% |  |  |  |  |
Sale Price Of Sold Property |  | $ 318,000 |  |  |  |  |
Mortgage Loan Related to Property Sales |  | $ 117,000 |  |  |  |  |
Net Rentable Area | ft² |  | 322,000 |  |  |  |  |
Proceeds from sales of real estate |  | $ 194,600 |  |  |  |  |
Gains on sales of real estate |  | 199,500 |  |  |  |  |
Noncontroling interest for a dissolved entity relcassed to accounts payable and and accrued expenses |  |  |  | 200 |  |  | $ 4,100
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] |  |  |  |  |  |  |
Property partnerships |  |  | 1,683,760 | 1,530,647 |  |  |
Proceeds from sales of real estate |  |  | 29,810 | 122,750 | 602,600 |  |
Gains on sales of real estate |  |  | 8,240 | $ 82,775 | $ 377,093 |  |
Boston Properties Limited Partnership | 505 9th Street [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Gains on sales of real estate |  | $ 199,700 |  |  |  |  |
Salesforce Tower | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Ownership Percentage | 5.00% |  |  |  |  |  |
Portion of project costs covered by a construction loan | 50.00% |  |  |  |  |  |
Portion of costs funded (in percentage) | 50.00% |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 3.00% |  |  |  |  |  |
Salesforce Tower | Boston Properties, Inc. [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Costs funded (in percentage) | 2.50% |  |  |  |  |  |
Preferred equity funded |  |  | $ 16,400 |  |  |  |
767 Fifth Avenue (the general motors building) [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Ownership Percentage by Parent |  |  |  |  |  | 60.00% |
Unpaid principal balance of the members' notes payable contributed to equity |  |  |  |  |  | $ 273,900 |
Property partnerships |  |  |  |  |  | 109,600 |
Consolidation, Eliminations [Member] | 767 Fifth Avenue (the general motors building) [Member] | Consolidated Properties [Member] |  |  |  |  |  |  |
Noncontrolling Interest [Line Items] |  |  |  |  |  |  |
Unpaid principal balance of the members' notes payable contributed to equity |  |  |  |  |  | $ 164,400 |

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