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Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands |  | 12 Months Ended |  |
--- | --- | --- | --- | ---
Jan. 08, 2024 | Dec. 31, 2023 | Dec. 14, 2023 | Dec. 31, 2022
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Other Liabilities |  |  | $ (445,947) |  | $ (450,918) |
Investments in unconsolidated joint ventures |  |  | 1,377,319 |  | 1,715,911 |
Investments In Affiliates Subsidiaries Associates And Joint Ventures net | [1] |  | 1,337,416 |  | 1,630,485 |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Other Liabilities |  |  | $ (39,900) |  | (85,400) |
Square 407 Limited Partnership [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Market Square North |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Other Liabilities | [1] |  | $ (5,996) |  | $ (6,198) |
BP/CRF Metropolitan Square LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Metropolitan Square |  |  |
Ownership Percentage | [2] |  |  |  | 20.00% |
Other Liabilities | [1] |  |  |  | $ (37,629) |
901 New York Avenue LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 901 New York Avenue |  |  |
Ownership Percentage | [3] |  | 25.00% |  |  |
Other Liabilities | [1] |  | $ (11,764) |  | $ (12,493) |
901 New York Avenue LLC (economic ownership) [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% |  | 50.00% |
WP Project Developer LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Wisconsin Place Land and Infrastructure |  |  |
Ownership Percentage | [4] |  | 33.33% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 30,375 |  | $ 31,971 |
500 North Capitol Venture LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 500 North Capitol Street, NW |  |  |
Ownership Percentage |  |  | 30.00% |  |  |
Other Liabilities | [1] |  | $ (10,253) |  | (9,185) |
501 K Street LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 1001 6th Street |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 44,774 |  | 42,922 |
Podium Developer LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | The Hub on Causeway - Podium |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 45,201 |  | 46,839 |
Residential Tower Developer LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Hub50House |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 40,235 |  | 45,414 |
Hotel Tower Developer LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | The Hub on Causeway - Hotel Air Rights |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 13,494 |  | 12,366 |
Office Tower Developer LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 100 Causeway Street |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 57,660 |  | 59,716 |
1265 Main Office JV LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 1265 Main Street |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 3,585 |  | 3,465 |
BNY Tower Holdings LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Dock 72 |  |  |
Ownership Percentage | [5] |  | 50.00% |  |  |
Other Liabilities | [1] |  | $ (11,890) |  | (19,921) |
CA-Colorado Center LLC[Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Colorado Center |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 237,815 |  | 233,862 |
7750 Wisconsin Avenue LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 7750 Wisconsin Avenue |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 50,064 |  | 52,152 |
BP-M 3HB Venture LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 3 Hudson Boulevard |  |  |
Ownership Percentage |  |  | 25.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 115,103 |  | $ 116,397 |
SMBP Venture LP [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Santa Monica Business Park |  |  |
Ownership Percentage | [6] |  |  |  | 55.00% |
Investments in unconsolidated joint ventures | [1] |  |  |  | $ 164,735 |
SMBP Venture LP [Member] | Joint Venture Partner [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  |  | 45.00% |  |
Platform 16 Holdings LP [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Platform 16 |  |  |
Ownership Percentage | [7],[8] |  | 55.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 45,564 |  | 158,109 |
Gateway Portfolio Holdings LLC [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Gateway Commons |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 376,834 |  | 324,038 |
Rosecrans-Sepulveda Partners 4, LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Beach Cities Media Campus |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 27,034 |  | 27,000 |
Safeco Plaza REIT LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Safeco Plaza |  |  |
Ownership Percentage | [8],[9] |  | 33.67% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 44,734 |  | 69,785 |
Safeco Plaza REIT LLC | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 33.00% |  |  |
360 PAS Holdco LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 360 Park Avenue South |  |  |
Ownership Percentage | [8],[10] |  | 71.11% |  |  |
Investments in unconsolidated joint ventures |  |  | $ 42,988 |  | $ 114,992 | [1]
Number of Promote Entities |  |  |  |  | 2 |
Payments to Acquire Real Estate and Real Estate Joint Ventures |  | $ 10,000 |  |  |  |
360 PAS Holdco LLC | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 35.79% |  | 35.79% |
360 PAS Holdco LLC | Joint Venture Partner [Member] | Scenario, Plan |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 29.00% |  |  |
PR II BXP Reston Gateway LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | Skymark - Reston Next Residential |  |  |
Ownership Percentage |  |  | 20.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 15,184 |  | $ 11,351 |
751 Gateway Holdings LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 751 Gateway |  |  |
Ownership Percentage |  |  | 49.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 93,411 |  | 80,714 |
200 Fifth Avenue JV LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 200 Fifth Avenue |  |  |
Ownership Percentage | [8] |  | 26.69% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 75,718 |  | $ 120,083 |
ABXP Worldgate Investments LLC |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Properties |  |  | 13100 and 13150 Worldgate Drive |  |  |
Ownership Percentage |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 17,546 |  |  |
Entity Owning Land And Infrastructure Of Project [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 33.33% |  |  |
Safeco Partner Entity One [Member] | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  |  |
Safeco Partner Entity Two | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  |  |
360 Park Avenue South Partners Entity | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  | 1.00% |
360 Park Avenue South Partners Entity Two | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  |  |  | 1.00% |
360 PAS Holdco LLC (indirect ownership) |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Number of joint venture partner(s) |  |  |  | 1 |  |
360 PAS Holdco LLC (indirect ownership) | Company's Share [Member] |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership Percentage |  |  | 35.02% |  | 5.837% |
[1] | Investments with deficit balances aggregating approximately $39.9 million and $85.4 million at December 31, 2023 and December 31, 2022, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2] | During the year ended December 31, 2023, the Company completed a restructuring of its ownership in Metropolitan Square, as described below in this Note 6.
[3] | The Company’s economic ownership increased based on the achievement of certain return thresholds. At December 31, 2023 and December 31, 2022, the Company’s economic ownership was approximately 50%. On January 8, 2024, the Company’s joint venture partner transferred all of its interest in the joint venture to the Company for a gross purchase price of $10.0 million, see Note 17 for more information.
[4] | The Company’s wholly-owned subsidiary that owns Wisconsin Place Office also owns a 33.33% interest in the joint venture entity that owns the land, parking garage and infrastructure of the project.
[5] | This property includes net equity balances from the amenity joint venture.
[6] | During the year ended December 31, 2023, the Company completed the acquisition of its joint venture partner’s 45% ownership interest in Santa Monica Business Park, as described below in this Note 6 and Note 3.
[7] | At December 31, 2022, this entity was a VIE.
[8] | During the year ended December 31, 2023, the Company recognized an other-than-temporary impairment loss on its investment.
[9] | The Company’s ownership includes (1) a 33.0% direct interest in the joint venture, and (2) an additional 1% interest in each of the two entities through which each partner owns its interest in the joint venture.
[10] | On December 14, 2023, the Company completed the acquisition of all of one of its joint venture partners ownership interest. As a result of this acquisition, at December 31, 2023, the Company’s ownership includes (1) a 35.79% direct interest in the joint venture, (2) an additional 35.02% indirect ownership in the joint venture, and (3) an additional 1% interest in the entity through which the partner owns its interest in the joint venture. The Company’s partner will fund required capital until its aggregate investment is approximately 29% of all capital contributions; thereafter, the partners will fund required capital according to their percentage interests. At December 31, 2022, the Company’s ownership included (1) a 35.79% direct interest in the joint venture, (2) an additional 5.837% indirect ownership in the joint venture, and (3) an additional 1% interest in each of the two entities through which each partner owns its interest in the joint venture.

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