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Investments in Unconsolidated Joint Ventures (Investments in Unconsolidated Joint Ventures) (Details) - USD ($) $ in Thousands |  | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Mar. 05, 2025 | Dec. 31, 2025 | Dec. 31, 2024 | Dec. 31, 2023 | Sep. 17, 2025 | Aug. 20, 2025 | Aug. 07, 2025 | Jun. 27, 2025 | Feb. 27, 2025
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Other Liabilities |  |  | $ (386,074) |  | $ (450,796) |  |  |  |  |  |  |
Investments in unconsolidated joint ventures |  |  | 999,309 |  | 1,093,583 |  |  |  |  |  |  |
Investments In Affiliates Subsidiaries Associates And Joint Ventures net | [1] |  | 983,710 |  | 1,060,074 |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  | $ 258,752 |  | 132,096 |  | $ 192,650 |  |  |  |  |
Square 407 Limited Partnership [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Market Square North |  |  |  |  |  |  |  |  |
Ownership Percentage | [2] |  | 50.00% |  |  |  |  |  |  |  |  |
Other Liabilities | [1] |  | $ 0 |  | (11,924) |  |  |  |  |  |  |
WP Project Developer LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Wisconsin Place Land and Infrastructure |  |  |  |  |  |  |  |  |
Ownership Percentage | [3] |  | 33.33% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 29,085 |  | 29,775 |  |  |  |  |  |  |
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] |  | $ (12,655) |  | (11,696) |  |  |  |  |  |  |
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] |  | $ 45,724 |  | 45,903 |  |  |  |  |  |  |
Podium Venture LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | The Hub on Causeway - Podium |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% | [4] |  |  |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 54,742 |  | 42,310 |  |  |  |  |  |  |
Residential Tower Developer LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Hub50House |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 33,942 |  | 42,493 |  |  |  |  |  |  |
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] |  | $ 12,021 |  | 14,271 |  |  |  |  |  |  |
Office Venture LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 100 Causeway Street |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% | [4] |  |  |  |  | 50.00% |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 48,924 |  | 55,810 |  |  |  |  |  |  |
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] |  | $ 3,091 |  | 3,476 |  |  |  |  |  |  |
BNY Tower Holdings LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Dock 72 |  |  |  |  |  |  |  |  |
Ownership Percentage | [5] |  | 50.00% |  |  |  |  |  |  |  |  |
Other Liabilities |  |  | $ (400) |  | (9,889) | [1] |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 83,547 |  |  |  |  |  |  |  |  |
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] |  | $ 69,959 |  | 65,000 |  |  |  |  |  |  |
7750 Wisconsin Avenue LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 7750 Wisconsin Avenue |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% |  |  |  |  |  |  |  |  | 50.00%
Investments in unconsolidated joint ventures | [1] |  | $ 47,144 |  | 48,423 |  |  |  |  |  |  |
BP-M 3HB Venture LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 3 Hudson Boulevard |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 25.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 109,451 |  | 112,771 |  |  |  |  |  |  |
Platform 16 Holdings LP [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Platform 16 |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 55.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 58,561 |  | 56,265 |  |  |  |  |  |  |
Gateway Portfolio Holdings LLC [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Gateway Commons |  |  |  |  |  |  |  |  |
Ownership Percentage | [6] |  | 50.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 125,576 |  | 272,000 |  |  |  |  |  |  |
Rosecrans-Sepulveda Partners 4, LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Beach Cities Media Campus |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 50.00% | [7] |  |  |  | 50.00% |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 272 |  | 27,051 |  |  |  |  |  |  |
Safeco Plaza REIT LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | Safeco Plaza |  |  |  |  |  |  |  |  |
Ownership Percentage | [8] |  | 33.67% |  |  |  |  |  |  |  |  |
Other Liabilities | [1] |  | $ (2,557) |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  |  |  | 0 |  |  |  |  |  |  |
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 |  |  | 71.11% | [9] |  |  |  |  |  | 71.11% |  |
Investments in unconsolidated joint ventures | [1] |  | $ 104,778 |  | 74,592 |  |  |  |  |  |  |
360 PAS Holdco LLC | Company's Share [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 35.79% |  |  |  |  |  |  |  |  |
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] |  | $ 14,506 |  | 14,844 |  |  |  |  |  |  |
751 Gateway Holdings LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 751 Gateway |  |  |  |  |  |  |  |  |
Ownership Percentage | [10] |  | 49.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 0 |  | 99,701 |  |  |  |  |  |  |
200 Fifth Avenue JV LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 200 Fifth Avenue |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 26.69% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 74,747 |  | 70,673 |  |  |  |  |  |  |
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] |  | $ 21,995 |  | 18,225 |  |  |  |  |  |  |
CAB 290 Coles Venture LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 290 Coles Street - Common Equity |  |  |  |  |  |  |  |  |
Ownership Percentage |  | 19.46% | 19.46% | [11] |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 19,928 |  |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  | $ 20,000 |  |  |  |  |  |  |  |  |  |
CAB 290 Coles Holdco LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 290 Coles Street - Preferred Equity |  |  |  |  |  |  |  |  |
Ownership Percentage | [11],[12] |  | 0.00% |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | [1] |  | $ 30,362 |  |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  | 29,900 |  |  |  |  |  |  |  |  |
CAB 290 Coles Holdco LLC | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Payments to Acquire Equity Method Investments |  |  | $ 65,000 |  |  |  |  |  |  |  |  |
Internal Rate of return on preferred equity |  |  | 13.00% |  |  |  |  |  |  |  |  |
17 Hartwell Avenue JV LLC |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Properties |  |  | 17 Hartwell Avenue |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 20.00% | [11] |  |  |  |  |  |  | 20.00% |
Investments in unconsolidated joint ventures | [1] |  | $ 10,567 |  |  |  |  |  |  |  |  |
Unconsolidated Joint Ventures [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Other Liabilities |  |  | $ (15,600) |  | $ (33,500) |  |  |  |  |  |  |
Entity Owning Land And Infrastructure Of Project [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 33.33% |  |  |  |  |  |  |  |  |
Safeco Partner Entity Two | Company's Share [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  |  |  |  |  |  |  |  |
360 PAS Holdco LLC (indirect ownership) | Company's Share [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 35.02% |  |  |  |  |  |  |  |  |
360 Park Avenue South Partners Entity | Company's Share [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  |  |  |  |  |  |  |  |
Safeco Partner Entity One [Member] | Company's Share [Member] |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Ownership Percentage |  |  | 1.00% |  |  |  |  |  |  |  |  |
[1] | Investments with deficit balances aggregating approximately $15.6 million and $33.5 million at December 31, 2025 and December 31, 2024, respectively, are included within Other Liabilities in the Company’s Consolidated Balance Sheets.
[2] | On November 10, 2025, the Company completed the sale of its ownership interest in the joint venture.
[3] | 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.
[4] | In conjunction with the execution of the mortgage loan on September 30, 2025 (described below), Podium Venture LLC and Office Venture LLC were created for structuring purposes and did not change any of the partner rights previously held by the partners of Podium Developer LLC or Office Tower Developer LLC, respectively.
[5] | This investment includes net equity balances from the amenity joint venture. The amenity joint venture had a deficit balance of approximately $0.4 million at December 31, 2025.
[6] | During the year ended December 31, 2025, the Company recognized an other-than-temporary impairment loss on its investment. On January 2, 2026, the Company completed the sale of its ownership interest in the joint venture (See Note 17).
[7] | On September 17, 2025, the joint venture completed the sale of the land parcel.
[8] | The Company’s ownership includes (1) a 33.0% direct interest in the joint venture, and (2) an additional 1.0% interest in each of the two entities through which each partner owns its interest in the joint venture.
[9] | 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 1.0% interest in the entity through which the partner owns its interest in the joint venture.
[10] | On December 30, 2025, the joint venture completed the sale of the property.
[11] | This entity is a VIE (See Note 2).
[12] | The Company agreed to fund up to $65.0 million of the required capital through its preferred equity investment. The Company’s preferred equity investment will earn and accrue a 13.0% internal rate of return (“IRR”) and is to be redeemed, in full, upon the earlier of two years after stabilization of the property or March 5, 2030.

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