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Investments in Unconsolidated Joint Ventures Narrative (Details) $ in Thousands |  |  |  | 9 Months Ended |  |
--- | --- | --- | --- | --- | --- | ---
Sep. 06, 2017 USD ($) ft² | Aug. 07, 2017 USD ($) ft² yr | Jul. 28, 2017 USD ($) ft² a Vehicles Buildings | Sep. 30, 2017 USD ($) | Sep. 30, 2016 USD ($) | Jul. 10, 2017 | Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  |  | $ 89,874 |  | $ 546,982 |  |
Proceeds from mortgage notes payable |  |  |  | 2,300,000 |  | 0 |  |
Cash held in escrow |  |  |  | 83,779 |  |  |  | $ 63,174
Capital distributions from unconsolidated joint ventures |  |  |  | $ 251,000 |  | 0 |  |
Podium Developer LLC [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Ownership Percentage | 50.00% |  |  | 50.00% |  |  |  |
Net Rentable Area (in sf) | ft² | 385,000 |  |  |  |  |  |  |
Colorado Center [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Vehicles In Structured Parking | Vehicles |  |  | 3,100 |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  | 50.00% |
number of buildings | Buildings |  |  | 6 |  |  |  |  |
Area of Land | a |  |  | 15 |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  | 1,118,000 |  |  |  |  |
7750 Wisconsin Avenue [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  | 50.00% | [1] |  |  |
Net Rentable Area (in sf) | ft² |  | 722,000 |  |  |  |  |  |
Term of Lease Signed (in years) | yr |  | 20 |  |  |  |  |  |
Payments and improvementst to enter into an equity method investments |  | $ 20,800 |  |  |  |  |  |
Cash held in escrow |  | $ 25,000 |  |  |  |  |  |
Secured Debt [Member] | Colorado Center [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Coupon/Stated Rate |  |  | 3.56% |  |  |  |  |
Proceeds from mortgage notes payable |  |  | $ 550,000 |  |  |  |  |
Capital distributions from unconsolidated joint ventures |  |  | 502,000 |  |  |  |  |
Boston Properties Limited Partnership |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  |  | $ 89,874 |  | 546,982 |  |
Proceeds from mortgage notes payable |  |  |  | 2,300,000 |  | 0 |  |
Cash held in escrow |  |  |  | 83,779 |  |  |  | $ 63,174
Capital distributions from unconsolidated joint ventures |  |  |  | $ 251,000 |  | $ 0 |  |
Boston Properties Limited Partnership | Secured Debt [Member] | Colorado Center [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Capital distributions from unconsolidated joint ventures |  |  | $ 251,000 |  |  |  |  |
Joint venture partner [Member] | 7750 Wisconsin Avenue [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Ownership Percentage |  | 50.00% |  |  |  |  |  |
Contribution of Property |  | $ 72,000 |  |  |  |  |  |
Payments and improvementst to enter into an equity method investments |  | 4,900 |  |  |  |  |  |
Capital distributions from unconsolidated joint ventures |  | 11,000 |  |  |  |  |  |
Secured Debt [Member] | Podium Developer LLC [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Construction Loan | $ 204,600 |  |  |  |  |  |  |
Coupon/Stated Rate | 2.25% |  |  |  |  |  |  |
Number of extensions | 2 |  |  |  |  |  |  |
Extension Option (in years) | 1 |  |  |  |  |  |  |
Colorado Center [Member] | Colorado Center [Member] |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  | 0.20% |
Payments to Acquire Equity Method Investments |  | $ 2,100 |  |  |  |  |  |
[1] | The entity is a VIE (See Note 2).

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