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Investment in Unconsolidated Joint Ventures (Narrative) (Details) $ in Thousands |  |  |  |  |  |  | 3 Months Ended | 6 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jun. 17, 2022 USD ($) | Jun. 16, 2022 USD ($) ft² | May 13, 2022 USD ($) loanExtension years | Apr. 18, 2022 USD ($) ft² | Mar. 28, 2022 USD ($) ft² loanExtension years | Mar. 27, 2022 USD ($) loanExtension years | Jun. 30, 2022 USD ($) | Jun. 30, 2021 USD ($) | Jun. 30, 2022 USD ($) | Jun. 30, 2021 USD ($) | Feb. 02, 2022 ft² | Jan. 18, 2022 ft² | Dec. 31, 2021 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage notes payable, net (amounts related to VIEs of $3,269,948 and $3,267,914 at June 30, 2022 and December 31, 2021, respectively) |  |  |  |  |  |  |  | $ 3,269,948 |  | $ 3,269,948 |  |  |  | $ 3,267,914
Payment for Debt Extinguishment or Debt Prepayment Cost |  |  |  |  |  |  |  |  |  | 0 | $ 185 |  |  |
Loss from early extinguishment of debt |  |  |  |  |  |  |  | $ 0 | $ 0 | $ 0 | (898) |  |  |
Gateway Commons Complex [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage | [1] |  |  |  |  |  |  | 50.00% |  | 50.00% |  |  |  |
Gateway Commons Complex [Member] | 651 Gateway | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  |  |  |  |  |  |  | 50.00% |
Platform 16 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage | [2] |  |  |  |  |  |  | 55.00% |  | 55.00% |  |  |  |
Platform 16 | Platform 16 | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  |  |  |  |  |  | 55.00% |  |
Net Rentable Area (in sf) | ft² |  |  |  |  |  |  |  |  |  |  |  | 1,100,000 |  |
BP/CRF Metropolitan Square LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  |  | 20.00% |  | 20.00% |  |  |  |
BP/CRF Metropolitan Square LLC [Member] | Metropolitan Square | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  | 20.00% |  |  |  |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  |  |  |  | 657,000 |  |  |  |  |  |  |  |
Mortgage notes payable, net (amounts related to VIEs of $3,269,948 and $3,267,914 at June 30, 2022 and December 31, 2021, respectively) |  |  |  |  |  | $ 420,000 | $ 294,100 |  |  |  |  |  |  |
Debt Instrument, Description of Variable Rate Basis |  |  |  |  |  |  | the greater of (x) LIBOR or (y) 0.65% |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  |  |  | 2.75% | 4.75% |  |  |  |  |  |  |
Number of extensions | loanExtension |  |  |  |  |  | 3 | 2 |  |  |  |  |  |  |
Extension Option (in years) | years |  |  |  |  |  | 1 | 1 |  |  |  |  |  |  |
Payment for Debt Extinguishment or Debt Prepayment Cost |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |
Loss from early extinguishment of debt |  |  |  |  |  | (1,300) |  |  |  |  |  |  |  |
Proceeds from mortgage notes payable |  |  |  |  |  | 100,500 |  |  |  |  |  |  |  |
Residential Tower Developer LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  |  |  |  | 50.00% |  | 50.00% |  |  |  |
Residential Tower Developer LLC [Member] | Hub50House [Member] | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  |  | 50.00% |  |  |  |  |  |  |  |  |
Proceeds from mortgage notes payable |  | $ 6,800 |  |  |  |  |  |  |  |  |  |  |  |
Residential Tower Developer LLC [Member] | Hub50House [Member] | Unconsolidated Properties | Interest Rate Swap |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative, Notional Amount |  | $ 185,000 |  |  |  |  |  |  |  |  |  |  |  |
Derivative, Forward Interest Rate |  | 4.432% |  |  |  |  |  |  |  |  |  |  |  |
Residential Tower Developer LLC [Member] | Hub50House [Member] | Unconsolidated Properties | Adjustable Rate Loans |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage notes payable, net (amounts related to VIEs of $3,269,948 and $3,267,914 at June 30, 2022 and December 31, 2021, respectively) |  | $ 185,000 | $ 176,700 |  | $ 176,500 |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  | 1.35% |  |  | 2.00% |  |  |  |  |  |  |  |  |
PR II BXP Reston Gateway LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage | [2],[3] |  |  |  |  |  |  | 20.00% |  | 20.00% |  |  |  |
751 Gateway Holdings LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage | [1] |  |  |  |  |  |  | 49.00% |  | 49.00% |  |  |  |
Joint Venture Partner [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Interest in Joint Venture |  |  |  | $ 500 |  |  |  |  |  |  |  |  |  |
Joint Venture Partner [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties | Scenario, Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 80.00% |  |  |  |  |  |  |  |  |  |
Payments to Acquire Interest in Joint Venture |  |  |  | $ 58,700 |  |  |  |  |  |  |  |  |  |
Joint Venture Partner [Member] | 751 Gateway Holdings LLC | 751 Gateway | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 51.00% |  |  |  |  |  |  |  |  |  |  |
Contribution of Property |  |  | $ 53,900 |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Interest in Joint Venture |  |  | $ 4,900 |  |  |  |  |  |  |  |  |  |  |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Mortgage notes payable, net (amounts related to VIEs of $3,269,948 and $3,267,914 at June 30, 2022 and December 31, 2021, respectively) |  |  |  |  |  |  |  | $ 3,413,562 |  | $ 3,413,562 |  |  |  | $ 3,214,961
Loss from early extinguishment of debt |  |  |  |  |  |  |  | 0 | $ 0 | (1,327) | $ 0 |  |  |
Unconsolidated Joint Ventures [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contribution of Property |  |  |  | 11,300 |  |  |  |  |  |  |  |  |  |
Construction Loan |  |  |  |  |  |  |  | $ 0 |  | $ 0 |  |  |  |
Unconsolidated Joint Ventures [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties | Scenario, Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Interest in Joint Venture |  |  |  | $ 3,500 |  |  |  |  |  |  |  |  |  |
Unconsolidated Joint Ventures [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties | Adjustable Rate Loans |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Debt Instrument, Basis Spread on Variable Rate |  |  |  | 2.00% |  |  |  |  |  |  |  |  |  |
Number of extensions | loanExtension |  |  |  | 2 |  |  |  |  |  |  |  |  |  |
Extension Option (in years) | years |  |  |  | 1 |  |  |  |  |  |  |  |  |  |
Debt Instrument, Unused Borrowing Capacity, Amount |  |  |  | $ 140,000 |  |  |  |  |  |  |  |  |  |
Unconsolidated Joint Ventures [Member] | 751 Gateway Holdings LLC | 751 Gateway | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 49.00% |  |  |  |  |  |  |  |  |  |  |
Contribution of Property |  |  | $ 53,900 |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Interest in Joint Venture |  |  | $ 2,600 |  |  |  |  |  |  |  |  |  |  |
Company's Share [Member] | BP/CRF Metropolitan Square LLC [Member] | Metropolitan Square |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from mortgage notes payable |  |  |  |  |  | $ 20,100 |  |  |  |  |  |  |  |
Company's Share [Member] | Residential Tower Developer LLC [Member] | Hub50House [Member] | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proceeds from mortgage notes payable |  | $ 3,400 |  |  |  |  |  |  |  |  |  |  |  |
Company's Share [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 96.00% |  |  |  |  |  |  |  |  |  |
Company's Share [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties | Scenario, Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  |  | 20.00% |  |  |  |  |  |  |  |  |  |
Construction | Gateway Commons Complex [Member] | 651 Gateway | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  |  |  |  |  |  |  |  |  |  |  | 327,000 |
Construction | Platform 16 | Platform 16 | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  |  |  |  |  |  |  |  |  |  | 390,000 |  |
Construction | 751 Gateway Holdings LLC | 751 Gateway | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  | 231,000 |  |  |  |  |  |  |  |  |  |  |
Construction | Unconsolidated Joint Ventures [Member] | PR II BXP Reston Gateway LLC | Reston Next Residential | Unconsolidated Properties | Scenario, Plan |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of Units in Real Estate Property |  |  |  | 508 |  |  |  |  |  |  |  |  |  |
Residential Building | Residential Tower Developer LLC [Member] | Hub50House [Member] | Unconsolidated Properties |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net Rentable Area (in sf) | ft² |  |  |  |  | 320,000 |  |  |  |  |  |  |  |  |
Number of Units in Real Estate Property |  |  |  |  | 440 |  |  |  |  |  |  |  |  |
[1] | On June 16, 2022, 751 Gateway was segregated from Gateway Commons into a single-purpose joint venture.
[2] | This entity is a VIE (See Note 2).
[3] | The Company’s partner will fund required capital until their aggregate investment is approximately 80% of all capital contributions; thereafter, the partners will fund required capital according to their percentage interests.

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